M Bonner Denton

Interests

Research

Research interests include analytical instrumentation, optical spectroscopy, mass spectrometry, separation science, scientific imaging and forensic analysis.

Courses

No activities entered.

Scholarly Contributions

Chapters

• Denton, M. B., & Ardelt, D. A. (2014). Solid State Array Detectors in Atomic Mass Spectroscopy. In ICP-MS.

Journals/Publications

• Denton, M., & Sperline, R. (2014). New CMOS Detectors are Impacting Atomic Spectroscopy. JAAS.
• Amsden, J. J., Herr, P. J., Landry, D. M., Kim, W., Vyas, R., Parker, C. B., Kirley, M. P., Keil, A. D., Gilchrist, K. H., Radauscher, E. J., Hall, S. D., Carlson, J. B., Baldasaro, N., Stokes, D., Di Dona, S. T., Russell, Z. E., Grego, S., Edwards, S. J., Sperline, R. P., , Denton, M. B., et al. (2018). Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector. Journal of the American Society for Mass Spectrometry, 29(2), 360-372.
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  Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified. Graphical Abstract ᅟ.
• Denton, M. B. (2018). A Call for More Science in Forensic Science. Proc Natl Acad Sci USA.
• Denton, M. B., Sah, S., Casadevall, A., Bell, S., Gates Jr., S. J., & Albright, T. D. (2017). Forensic Science Must Be Scientific. Scientific American, 317(4).
• Denton, M. B., Radauscher, E. J., Parker, C. B., Gilchris, K. H., Dona, S. D., Russell, Z. E., Hall, S. D., Carlson, J. B., Grego, S., Edwards, S. J., Sperline, R. P., Stoner, B. R., Glass, J. T., & Amsden, J. J. (2017). A miniature electron ionization source fabricated using microelectromechanical systems (MEMS) with integrated carbon nanotube (CNT) field emission cathodes and low-temperature co-fired ceramics (LTCC). International Journal of Mass Spectrometry, 8. doi:10.1016/j.ijms.2016.10.021
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  The use of microelectromechanical systems (MEMS) components in miniature mass spectrometers is particularly attractive due to their small size and scalable manufacturing capability. Our group has pioneered the development of miniature electron ionization sources combining MEMS fabricated structures with integrated carbon nanotube (CNT) cold-cathode field emitters. However, until now they have been of limited use due to the limited ability to direct the ions into a mass analyzer. In this work, we design a miniature ion source using a microfabricated MEMS device and a low temperature co-fired ceramic (LTCC) carrier that includes electrical connections, ion optics for directing ions out of the device, and a sample inlet. We present the design and fabrication of the ion source; simulate the energy and angular dispersion; and experimentally determine the energy and angular dispersion.
• Denton, M. B., Saka, M. J., & Albreight, T. (2016). Forensic bitemark identification: weak foundations, exaggerated claims. J. Law Biosci.. doi:10.1093/jlb/lsw045
• Denton, M. (2012). The Impact of Focal Plane Arrays on Chemical Analysis: Today and Tomorrow. Proceedings, Scientific Detectors in Astronomy Workshop.
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  Location: Florence, Italy
• Felton, J. A., Schilling, G. D., Ray, S. J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2011). Evaluation of a fourth-generation focal plane camera for use in plasma-source mass spectrometry. Journal of Analytical Atomic Spectrometry, 26(2), 300-304.
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  Abstract: A fourth-generation focal plane camera containing 1696 Faraday-strip detectors was fitted to a Mattauch-Herzog mass spectrograph and characterized for its performance with inductively coupled plasma ionization. The camera provides limits of detection in the single to tens of ng L-1 range for most elements and has a linear dynamic range of at least nine orders of magnitude. Isotope-ratio precision better than 0.02% has also been achieved with this device, and this fourth-generation system features the broadest simultaneous mass range obtainable to date with this family of focal plane camera detectors. © 2011 The Royal Society of Chemistry.
• Lorincik, J., Denton, M. B., Sperline, R. P., Young, E. T., & Williams, P. (2011). Testing of a micro Faraday cup array for ion detection in SIMS. Analytical Letters, 44(6), 1050-1057.
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  Abstract: A micro-Faraday array detector (row of miniature 32 thin film strip electrodes wire bonded to an on-chip integrated capacitance transimpedance amplifier) was tested for use in a multiple collector secondary ion mass spectrometry. The detector was mounted on a standard IMS3f SIMS instrument in place of a microchannel plate. The measurements were performed by using a silicon sample bombarded by either O+2 or Cs+ primary ions with or without D2O flooding and detecting secondary ions of Si±, SiH±, O-, SiD-, OD-. A parallel detection of near masses of 29Si and 28SiH or 18O and 16OD was demonstrated at a sensitivity level ~230 counts/s. © Taylor & Francis Group.
• Rubinshtein, A. A., Schilling, G. D., Ray, S. J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2010). Characterization of a third-generation Faraday-strip array detector coupled to a Mattauch-Herzog geometry mass spectrograph with a dc-glow discharge ionization source. Journal of Analytical Atomic Spectrometry, 25(5), 735-738.
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  Abstract: A third-generation Faraday-strip array detector has been coupled to a Mattauch-Herzog mass spectrometer and dc glow-discharge ionization source. This combination offers simultaneous determination of multiple elements directly from solid samples and provides superior resolving power and improved limits of detection over previous generations of array detectors. With the third-generation detector array, resolving power is limited only by the mass spectrometer and not by the array. Because of this enhanced resolution, limits of detection, especially for higher mass-to-charge ratios, were improved. Isotope-ratio precision was found to be 0.07% RSD on average and quantitative response was linear over 5 orders of magnitude. © The Royal Society of Chemistry 2010.
• Schilling, G. D., Ray, S. J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2010). Optimization of Ag isotope-ratio precision with a 128-channel array detector coupled to a mattauch-herzog mass spectrograph. Journal of Analytical Atomic Spectrometry, 25(3), 322-327.
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  Abstract: Isotope-ratio measurements are necessary in a wide range of applications. The precision of these measurements is of utmost importance because it governs the ability to distinguish differences between samples. Often, simultaneous isotope detection is necessary to reach the precision values needed for an analysis to be conclusive. Furthermore, the more isotope ratios that can be precisely determined at once, the better the chances of distinguishing between samples. Therefore, detector arrays, able to simultaneously monitor a broad range of isotopes, are attractive. Such an array detector, termed the focal plane camera (FPC), has been shown to be capable of achieving impressive precision values (0.02% RSD) within relatively short integration times (200 s). However, because the channels of the FPC array detector are inherently discrete, optimization of peak integration methods is important. This paper compares isotope-ratio precision values based on different peak integration methods of raw and zero-filled interpolated data. Also, problems associated with peak drift are explored and the use of flat-topped peak shapes for improved isotope-ratio precision levels are investigated. © 2010 The Royal Society of Chemistry.
• Schilling, G. D., Shelley, J. T., H., J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2010). Detection of Positive and Negative Ions from a Flowing Atmospheric Pressure Afterglow Using a Mattauch-Herzog Mass Spectrograph Equipped with a Faraday-Strip Array Detector. Journal of the American Society for Mass Spectrometry, 21(1), 97-103.
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  PMID: 19889553;Abstract: An ambient desorption/ionization (ADI) source, known as the flowing atmospheric pressure afterglow (FAPA), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) equipped with a focal plane camera (FPC) array detector. The FAPA ionization source enables direct mass spectral analysis of solids, liquids, and gases through either positive or negative ionization modes. In either case, spectra are generally simple with dominant peaks being the molecular ions or protonated molecular ions. Use of the FAPA source with the MHMS allows the FPC detector to be characterized for the determination of molecular species, whereas previously only atomic mass spectrometry (MS) has been demonstrated. Furthermore, the FPC is shown to be sensitive to negative ions without the need to change any detector parameters. The analysis of solid, liquid, and gaseous samples through positive and negative ionization is demonstrated with detection limits (1-25 fmol/s, ∼0.3-10 pg of analyte per mL of helium) surpassing those obtained with the FAPA source coupled to a time-of-flight mass analyzer. © 2010 American Society for Mass Spectrometry.
• Babis, J. S., Sperline, R. P., Knight, A. K., Jones, D. A., Gresham, C. A., & Denton, M. B. (2009). Performance evaluation of a miniature ion mobility spectrometer drift cell for application in hand-held explosives detection ion mobility spectrometers. Analytical and Bioanalytical Chemistry, 395(2), 411-419.
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  PMID: 19424683;Abstract: The implementation of hand-held ion mobility spectrometers (IMS) requires the development and evaluation of miniature drift cells providing high sensitivity while maintaining reasonable resolution. This manuscript describes the construction of a miniature IMS designed for such an application and its characterization by evaluation of the detection limits and resolution of the system with seven explosive compounds including trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl), nitroglycerin (NG), 2,4-dinitrotoluene (2,4 DNT), and 2,6-dinitrotoluene (2,6 DNT). © 2009 Springer-Verlag.
• Schilling, G. D., Ray, S. J., Rubinshtein, A. A., Felton, J. A., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2009). Evaluation of a 512-channel Faraday-strip array detector coupled to an inductively coupled plasma Mattauch-Herzog mass spectrograph. Analytical Chemistry, 81(13), 5467-5473.
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  PMID: 19462968;Abstract: A 512-channel Faraday-strip array detector has been developed and fitted to a Mattauch-Herzog geometry mass spectrograph for the simultaneous acquisition of multiple mass-to-charge values. Several advantages are realized by using simultaneous detection methods, including higher duty cycles, removal of correlated noise, and multianalyte transient analyses independent of spectral skew. The new 512-channel version offers narrower, more closely spaced pixels, providing improved spectral peak sampling and resolution. In addition, the electronics in the amplification stage of the new detector array incorporate a sample-and-hold feature that enables truly simultaneous interrogation of all 512 channels. While sensitivity and linear dynamic range remain impressive for this Faraday-based detector system, limits of detection and isotope ratio data have suffered slightly from leaky p-n junctions produced during the manufacture of the semiconductor-based amplification and readout stages. This paper describes the new 512-channel detector array, the current dominant noise sources, and the figures of merit for the device as pertaining to inductively coupled plasma ionization. © 2009 American Chemical Society.
• Schilling, G. D., Shelley, J. T., A., J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2009). Use of an ambient ionization flowing atmospheric-pressure afterglow source for elemental analysis through hydride generation. Journal of Analytical Atomic Spectrometry, 24(1), 34-40.
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  Abstract: An ambient mass spectrometry ionization source based on an atmospheric-pressure flowing afterglow has been coupled to a Mattauch-Herzog mass spectrograph capable of simultaneous acquisition of a range of mass-to-charge values by means of a Faraday-strip array detector. The flowing afterglow was used as the ionization pathway for species produced by hydride generation. This ionization strategy circumvents problems, such as discharge instabilities or memory effects, induced by introducing the gaseous sample into the discharge. The generated spectra show both atomic and molecular peaks; calibration curves were calculated for both peak types with limits of detection for arsenic below 10 ppb. This study demonstrates the ability to use an ambient mass spectrometry source, commonly used for molecular analyses, for the detection of gas phase elemental species with the possibilty of performing speciation by coupling with a separation technique. © The 2009 Royal Society of Chemistry.
• Pommier, C. J., Redhammer, G. J., Denton, M. B., & Downs, R. T. (2008). Raman spectroscopic and visible absorption investigation of LiCrSi ₂O₆ pyroxene under pressure. Applied Spectroscopy, 62(7), 766-772.
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  PMID: 18935826;Abstract: The first observation of the vibrational spectrum of the synthetic pyroxene Li-kosmochlor (LiCrSi2O6) is reported herein. The Raman and visible spectra are reported as a function of pressure. Though the pyroxene retains its P21/c symmetry, changes in the Raman spectra are observed between 6.8 and 7.7 GPa, possibly due to the formation of an additional bond between Li and 03 or some other transition that retains the mineral's P2 1/c space group. Splitting of the peak appearing at approximately 700 cm-1, used to characterize the P21/e phase in other studies, is not observed. Comparison is made with the Raman spectra of LiAlSi2O6 and LiFeSi2O6 in the P21/c phase and the visible spectra of NaCiSi2O 6, at high pressures. ©2008 Society for Applied Spectroscopy.
• Denson, S. C., Pommier, C. J., & Denton, M. B. (2007). The impact of array detectors on Raman spectroscopy. Journal of Chemical Education, 84(1), 67-74.
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  Abstract: Raman spectroscopy has been reborn owing to improvements in lasers, optics, and detectors. Whereas Raman scattering was once considered an obscure technique, it is now thought, by many, to be just as useful as infrared analysis. Array detectors have resulted in greatly reduced measurement times not only because full spectra are collected without scanning, but also because they possess extreme sensitivity and have low noise. The incredible sensitivity of modern array detectors has allowed Raman spectroscopy to be used to detect compounds at part per million concentrations and to perform Raman analyses at advantageous wavelengths that were once nearly impossible to detect. Some of the newer applications, such as simultaneous collection of multiple spectra and Raman imaging, would be nearly impossible without two-dimensional array detectors. Array detectors are not solely responsible for the resurgence of Raman spectroscopy, but there can be no doubt of the tremendous impact array detectors have on Raman spectroscopy.
• Schilling, G. D., Andrade, F. J., H., J., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2007). Continuous simultaneous detection in mass spectrometry. Analytical Chemistry, 79(20), 7662-7668.
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  PMID: 17877420;Abstract: In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously and continuously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry. © 2007 American Chemical Society.
• Peschel, B. U., Andrade, F., Wetzel, W. C., Schilling, G. D., Hieftje, G. M., Broekaert, J. A., Sperline, R., Denton, M. B., Barinaga, C. J., & Koppenaal, D. W. (2006). Electrothermal vaporization coupled with inductively coupled plasma array-detector mass spectrometry for the multielement analysis of Al ₂O₃ ceramic powders. Spectrochimica Acta - Part B Atomic Spectroscopy, 61(1), 42-49.
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  Abstract: An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP-MS) equipped with an array detector. The ability of this instrument to record the transient signals produced for a number of analytes in ETV-ICP-MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4-60 pg μL- 1 for aqueous solutions and in the low μg g- 1 range for the analysis of 10 mg mL- 1 slurries of Al2O3 powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3-5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al 2O3 powders at the 2-270 μg g- 1 level without the use of thermochemical reagents. The results well agree with literature values for Fe and Cu, whereas deviations of 50% at the 90 μg g- 1 level for Ga were found. © 2005 Elsevier B.V. All rights reserved.
• Schilling, G. D., Andrade, F. J., Barnes, J. H., Sperline, R. P., Denton, M. B., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2006). Characterization of a second-generation focal-plane camera coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph. Analytical Chemistry, 78(13), 4319-4325.
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  PMID: 16808438;Abstract: A second-generation Faraday-strip array detector has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph, thereby offering simultaneous acquisition of a range of mass-to-charge ratios. The second-generation device incorporates narrower, more closely spaced collectors than the earlier system. Furthermore, the new camera can acquire signal on all collectors at a frequency greater than 2 kHz and has the ability to independently adjust the gain level of each collector. Each collector can also be reset independently. With these improvements, limits of detection in the hundreds of picograms per liter for metals in solution have been obtained. Some additional features, such as a broader linear dynamic range (over 7 orders of magnitude), greater resolving power (up to 600), and improved isotope ratio accuracy were attained. In addition, isotope ratio precision as low as 0.018% RSD was achieved. © 2006 American Chemical Society.
• Finch, J. W., Toerne, K. A., Schram, K. H., & Denton, M. B. (2005). Evaluation of a hydrogen laser vacuum ultraviolet source for photoionization mass spectrometry of pharmaceuticals. Rapid Communications in Mass Spectrometry, 19(1), 15-22.
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  PMID: 15573417;Abstract: A photoionization hydrogen laser time-of-flight mass spectrometer system (H2-TOFMS) has been evaluated for the rapid analysis of drugs of abuse and pharmaceutical agents extracted from prescription tablets and spiked urine samples. The spectra obtained using the H2-TOFMS showed primarily intact molecular ions (M+) after introduction by a heated probe and irradiation with vacuum ultraviolet (VUV) photons from the laser. Samples analyzed by this technique required only a simple solid-phase extraction step; no chromatographic separation or derivatization was necessary to identify the drugs of abuse or pharmaceutical agents. Copyright © 2004 John Wiley & Sons, Ltd.
• Hanley, Q. S., & Denton, M. B. (2005). Advances in array detectors for X-ray diffraction techniques. Journal of Synchrotron Radiation, 12(5), 618-625.
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  PMID: 16120985;Abstract: Improved focal plane array detector systems are described which can provide improved readout speeds, random addressing and even be employed to simultaneously measure position, intensity and energy. This latter capability promises to rekindle interests in Laue techniques. Simulations of three varieties of foil mask spectrometer in both on- and off-axis configurations indicate that systems of stacked silicon detectors can provide energy measurements within 1 % of the true value based on the use of single 'foils' and ∼ 10000 photons. An eight-detector hybrid design can provide energy coverage from 4 to 60 keV. Energy resolution can be improved by increased integration time or higher flux experiments. An off-axis spectrometer design in which the angle between the incident beam and the detector system is 45° results in a shift in the optimum energy response of the spectrometer system. In the case of a 200 μm-thick silicon absorber, the energy optimum shifts from 8.7 keV to 10.3 keV as the angle of incidence goes from 0 to 45°. These new designs make better use of incident photons, lower the impact of source flicker through simultaneous rather than sequential collection of intensities, and improve the energy range relative to previously reported systems. © 2005 International Union of Crystallography Printed in Great Britain - all rights reserved.
• J., C., Downs, R. T., Stimpfl, M., Redhammer, G. J., & Denton, M. B. (2005). Raman and X-ray investigations of LiFeSi₂O₆ pyroxene under pressure. Journal of Raman Spectroscopy, 36(9), 864-871.
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  Abstract: In situ Raman spectroscopy at high pressure was utilized to follow the phase transition of a synthetic sample of Li-aegerine pyroxene (LiFeSi 2O6) from its low-pressure (C2/c) phase to its high-pressure (P21/c) phase. The phase change occurred between 0.7 and 1 GPa and was accompanied by a change in coordination of the Li atom from 4 to 5, which was confirmed by single-crystal X-ray diffraction. This is the first report of the Raman spectrum of Li-aegerine in the P21/c phase. As was previously observed with other pyroxenes, additional changes in the Raman spectra were observed at pressures higher than the phase transition, including the splitting of the peak near 700 cm-1, which has traditionally been utilized to indicate the phase transition. Comparisons with the Raman spectra of spodumene in both symmetries are utilized for a discussion of modes. Copyright © 2005 John Wiley & Sons, Ltd.
• Koppenaal, D. W., Barinaga, C. J., Denton, M. B., Sperline, R. P., Hieftje, G. M., Schilling, G. D., Andrade, F. J., & H., J. (2005). MS detectors. Analytical Chemistry, 77(21), 418 A-427 A.
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  Abstract: In MS, ion generation and separation have received most of the attention. David W. Koppenaal and colleagues at Pacific Northwest National Laboratory, the University of Arizona, Indiana University, and Los Alamos National Laboratory review current MS detector technology and discuss concepts on the horizon that will allow MS to see the forest, the trees, and all the leaves. © 2005 American Chemical Society.
• Sperline, R. P., Knight, A. K., Gresham, C. A., Koppenaal, D. W., Hieftje, G. M., & Denton, M. B. (2005). Read-noise characterization of focal plane array detectors via mean-variance analysis. Applied Spectroscopy, 59(11), 1315-1323.
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  PMID: 16316508;Abstract: Mean-variance analysis is described as a method for characterization of the read-noise and gain of focal plane array (FPA) detectors, including charge-coupled devices (CCDs), charge-injection devices (CIDs), and complementary metal-oxide-semiconductor (CMOS) multiplexers (infrared arrays). Practical FPA detector characterization is outlined. The nondestructive readout capability available in some CIDs and FPA devices is discussed as a means for signal-to-noise ratio improvement. Derivations of the equations are fully presented to unify understanding of this method by the spectroscopic community. © 2005 Society for Applied Spectroscopy.
• George, G. N., Prince, R. C., Gailer, J., Buttigieg, G. A., Denton, M. B., Harris, H. H., & Pickering, I. J. (2004). Mercury binding to the chelation therapy agents DMSA and DMPS and the rational design of custom chelators for mercury. Chemical Research in Toxicology, 17(8), 999-1006.
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  PMID: 15310232;Abstract: Clinical chelation therapy of mercury poisoning generally uses one or both of two drugs-meso-dimercaptosuccinic acid (DMSA) and dimercaptopropanesulfonic acid (DMPS), commercially sold as Chemet and Dimaval, respectively. We have used a combination of mercury Lin-edge X-ray absorption spectroscopy and density functional theory calculations to investigaite the chemistry of interaction of mercuric ions with each of these chelation therapy drugs. We show that neither DMSA nor DMPS forms a true chelate complex with mercuric ions and that these drugs should be considered suboptimal for their clinical task of binding mercuric ions. We discuss the design criteria for a mercuric specific chelator molecule or "custom chelator", which might form the basis for an improved clinical treatment.
• H, J., Schilling, G. D., Stone, S. F., Sperline, R. P., Denton, M. B., Young, E. T., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2004). Simultaneous multichannel mass-specific detection for high-performance liquid chromatography using an array detector sector-field mass spectrometer.. Analytical and bioanalytical chemistry, 380(2), 227-234.
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  PMID: 15551077;Abstract: The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP-MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP-MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity.
• H., J., Schilling, G. D., Hieftje, G. M., Sperline, R. P., Denton, M. B., Barinaga, C. J., & Koppenaal, D. W. (2004). Use of a novel array detector for the direct analysis of solid samples by laser ablation inductively coupled plasma sector-field mass spectrometry. Journal of the American Society for Mass Spectrometry, 15(6), 769-776.
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  PMID: 15144966;Abstract: The use of laser ablation (LA) as a sample-introduction method for inductively coupled plasma mass spectrometry (ICP-MS) creates a powerful tool for trace elemental analysis. With this type of instrument, high analyte spatial resolution is possible in three dimensions with ng/g limits of detection and minimal sample consumption. Here, simultaneous detection is used to eliminate the correlated noise that plagues the ablation process. This benefit allows analyses to be performed with single laser pulses, resulting in improved depth resolution, even less sample consumption, and improved measurement precision. The new instrument includes an LA sample-introduction system coupled to an ICP ionization source and a Mattauch-Herzog mass spectrograph (MHMS) fitted with a novel array detector. With this instrument, absolute limits of detection are in the tens to hundreds of fg regime and isotope-ratio precision is better than 0.02% RSD with a one-hour integration period. Finally, depth-profile analysis has been performed with a depth resolution of 5 nm per ablation event. © 2004 American Society for Mass Spectrometry.
• H., J., Schilling, G. D., Sperline, R. P., Denton, M. B., Young, E. T., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2004). Coupling of a gas Chromatograph to a simultaneous-detection inductively coupled plasma mass spectrograph for speciation of organohalide and organometallic compounds. Journal of Analytical Atomic Spectrometry, 19(6), 751-756.
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  Abstract: A gas Chromatograph (GC) has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph (ICP-MHMS) equipped with a novel detector array. In its current state of development the detector array, termed the focal plane camera (FPC), permits the simultaneous monitoring of up to 15 m/z: values. A heated line was used to transfer the capillary-column effluent from the GC to the ICP torch, though due to instrument operating conditions, the transfer line was terminated 50 mm ahead of the ICP torch. Minimal tailing was observed, with the most severe effect seen for high-boiling analytes. With this coupling, absolute limits of detection are in the tens to hundreds of femtogram regime for organometallic species and in the single picogram regime for halogenated hydrocarbons. © The Royal Society of Chemistry 2004.
• H., J., Schilling, G. D., Sperline, R., Denton, M. B., Young, E. T., Barinaga, C. J., Koppenaal, D. W., & Hieftje, G. M. (2004). Characterization of a Focal Plane Camera Fitted to a Mattauch-Herzog Geometry Mass Spectrograph. 2. Use with an Inductively Coupled Plasma. Analytical Chemistry, 76(9), 2531-2536.
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  PMID: 15117194;Abstract: A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) with an inductively coupled plasma ionization source. The FPC employs an array of gold Faraday cups, each with its own charge. integrating circuit that allows the simultaneous detection of several m/z ratios. The ion-sampling interface of the MHMS has been redesigned to provide better heat transfer away from the sampler and skimmer cones and to reduce the negative effects of turbulent gas flows around the plasma. The instrument has produced limits of detection in the tens to hundreds of parts per quadrillion regime and isotope ratio accuracy and precision of 5% error and 0.007% RSD, respectively. Limits of detection with the FPC are comparable to those obtained with a single-channel secondary electron multiplier (SEM). However, the isotope ratio accuracy and precision are better with the FPC than when the SEM is employed. The dynamic range has been shown to be linear over 7 orders of magnitude.
• Buttigieg, G. A., Baker, M. E., Ruiz, J., & Denton, M. B. (2003). Lead isotope ratio determination for the forensic analysis of military small arms projectiles. Analytical Chemistry, 75(19), 5022-5029.
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  Abstract: A study focusing on the ability to utilize isotopic analysis of Pb used in small arms projectiles from varying geographic origin was undertaken using the GV Instruments Isoprobe multicollector inductively coupled plasma mass spectrometer. With the exception of two classes of ammunition, these samples were able to be distinguished from one another. Also, following rigorous normalization and mass bias correction, these data were compared to data collected by geochemists in localities corresponding to projectile manufacture. This comparison was successful when projectiles in certain economically isolated countries were analyzed. Pb isotopic analysis with MC-ICPMS is shown to be useful as a tool for distinguishing between ammunition of various manufacturing origins.
• Buttigieg, G. A., Knight, A. K., Denson, S., Pommier, C., & Denton, M. B. (2003). Characterization of the explosive triacetone triperoxide and detection by ion mobility spectrometry. Forensic Science International, 135(1), 53-59.
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  PMID: 12893136;Abstract: The improvised explosive triacetone triperoxide (TATP) was synthesized and characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Raman and infrared (IR) spectroscopy. Triacetone triperoxide was subsequently analyzed by ion mobility spectrometry (IMS) in positive ion mode, and detected as a cluster of three peaks with a drift time of the most intense peak at 13.06ms. Triacetone triperoxide was then analyzed after dissolution in toluene, where a dramatic increase in peak intensity was observed, at a flight time of 12.56ms (K0=2.71cm2V-1s-1). Triacetone triperoxide was subsequently analyzed by coupling the ion mobility spectrometer to a triple quadrupole mass spectrometer, where a single peak at m/z of 223 atomic mass units identified the species present in the ion mobility spectra as being triacetone triperoxide. © 2003 Elsevier Ireland Ltd. All rights reserved.
• Denton, M. B. (2003). Improved analytical instrumentation: Potential for impact in biological sciences. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS, 1, 236-237.
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  Abstract: New approaches for implementing advanced detectors for mass spectrometry and ion mobility spectrometry are described. These detectors that have been implemented using technologies originally developed for advanced visible CCDs and infrared arrays hold great promise for vastly improving many areas of mass spectrometry. Current trends are assessed and employed to predict future application of improved focal plane arrays to modern chemical analysis.
• Denton, M. B., Sperline, R. P., Giles, J. H., Gilmore, D. A., J., C., & Downs, R. T. (2003). Advances in the application of array detectors for improved chemical analysis, part I. Comparison of qualitative analyses using large, computer-based Raman spectral libraries. Australian Journal of Chemistry, 56(2-3), 117-131.
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  Abstract: Although a mature technique, Raman spectroscopy remains not widely used as a routine analytical technique. The advantages of Raman spectroscopy, such as minimal sample preparation and relatively uncomplicated spectra, combined with technical advances, including more stable diode lasers, higher quality filters, and better polychromators and array detectors, have led to a renaissance in sensitive and versatile Raman spectrometers. The lack of appropriate databases for routine analysis, which represents the last barrier to the technique's widespread use, is beginning to be overcome, as described in this review.
• Denton, M., Buttigieg, G. A., Knight, A. K., Denson, S., Pommier, C., & Denton, M. B. (2003). Characterization of the explosive triacetone triperoxide and detection by ion mobility spectrometry. Forensic science international, 135(1).
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  The improvised explosive triacetone triperoxide (TATP) was synthesized and characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Raman and infrared (IR) spectroscopy. Triacetone triperoxide was subsequently analyzed by ion mobility spectrometry (IMS) in positive ion mode, and detected as a cluster of three peaks with a drift time of the most intense peak at 13.06 ms. Triacetone triperoxide was then analyzed after dissolution in toluene, where a dramatic increase in peak intensity was observed, at a flight time of 12.56 ms (K0=2.71 cm2V(-1)s(-1)). Triacetone triperoxide was subsequently analyzed by coupling the ion mobility spectrometer to a triple quadrupole mass spectrometer, where a single peak at m/z of 223 atomic mass units identified the species present in the ion mobility spectra as being triacetone triperoxide.
• Gailer, J., Buttigieg, G. A., & Denton, M. B. (2003). Simultaneous arsenic- and selenium-specific detection of the dimethyldiselenoarsinate anion by high-performance liquid chromatography-inductively coupled plasma atomic emission spectrometry. Applied Organometallic Chemistry, 17(8), 570-574.
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  Abstract: The seleno-bis (S-glutathionyl) arsinium ion, [(GS)2AsSe]-, which can be synthesized from arsenite, selenite and glutathione (GSH) at physiological pH, fundamentally links the mammalian metabolism of arsenite with that of selenite and is potentially involved in the chronic toxicity/carcinogenicity of inorganic arsenic. A mammalian metabolite of inorganic arsenic, dimethylarsinic acid, reacts with selenite and GSH in a similar manner to form the dimethyldiselenoarsinate anion, [(CH3)2As(Se)2]-. Since dimethylarsinic acid is an environmentally abundant arsenic compound that could interfere with the mammalian metabolism of the essential trace element selenium via the in vivo formation of [(CH3)2As(Se)2]-, a chromatographic method was developed to rapidly identify this compound in aqueous samples. Using an inductively coupled plasma atomic emission spectrometer (ICP-AES) as the simultaneous arsenic- and selenium-specific detector, the chromatographic retention behaviour of [(CH3)2As(Se)2]- was investigated on styrene-divinylbenzene-based high-performance liquid chromatography (HPLC) columns. With a Hamilton PRP-1 column as the stationary phase (250 × 4.1 mm ID, equipped with a guard column) and a phosphate-buffered saline buffer (0.01 mol dm-3, pH 7.4) as the mobile phase, [(CH3)2As(Se)2]- was identified in the column effluent according to its arsenic: selenium molar ratio of 1:2. With this stationary phase/mobile phase combination, [(CH3)2As(Se)2]- was baseline-separated from arsenite, selenite, dimethylarsinate, methylarsonate and low molecular weight thiols (GSH, oxidized GSH) that are frequently encountered in biological samples. Thus, the HPLC-ICP-AES method developed should be useful for rapid identification and quantification of [(CH3)2As(Se)2]- in biological fluids. Copyright © 2003 John Wiley & Sons, Ltd.
• H., J., Hieftje, G. M., Denton, M. B., Sperline, R., Koppenaal, D. W., & Barinaga, C. (2003). A mass spectrometry detector array that provides truly simultaneous detection. American Laboratory, 35(20), 15-22.
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  Abstract: A mass spectrometry detector array that provides truly simultaneous detection was discussed. Although still in its initial stages of development, the FPC has already shown wide utility as a mass spectrometry detector. It has demonstrated figures of merit that are comparable to those obtainable with a state-of-the-art single channel detector. Moreover, it has demonstrated improved measurement precision and the accurate recording of fast transient signals.
• H., J., Schilling, G. D., Denton, M. B., Koppenaal, D. W., & Hieftje, G. M. (2003). Development and characterization of an electrostatic quadrupole extraction lens for mass spectrometry. Journal of Analytical Atomic Spectrometry, 18(9), 1015-1018.
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  Abstract: A new ion optical element for mass spectrometry has been developed to increase ion-beam transmission into the high-vacuum region of a mass spectrometer. The optic, termed the electrostatic quadrupole extraction lens (EQEL), incorporates quadrupole-like focusing fields into a conventional extraction element. These fields have been established by purposefully positioning openings in an extraction optic and surrounding the optic with a solid, cylindrical barrel unit. Modeling of the EQEL optic shows several regions of high ion beam transmission while, experimentally, the EQEL provides a 35-fold improvement over a conventional extraction optic when used with a glow discharge Mattauch-Herzog geometry mass spectrograph. © The Royal Society of Chemistry 2003.
• Origlieri, M. J., Downs, R. T., Thompson, R. M., J., C., Denton, M. B., & Harlow, G. E. (2003). High-pressure crystal structure of kosmochlor, NaCrSi₂O₆, and systematics of anisotropric compression in pyroxenes. American Mineralogist, 88(7), 1025-1032.
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  Abstract: The crystal structure of synthetic kosmochlor, NaCrSi2O6, was studied using single crystal X-ray diffraction at high pressure. A four-pin diamond anvil cell, with 4:1 methanol:ethanol pressure medium, was used to achieve pressures to 9.28 GPa. Unit-cell data were collected at 20 pressures, and intensity data were collected at 13 of these pressures. Fitting the P-V data to a third-order Birch-Murnaghan equation yields Vo = 418.84(3) Å3, Kc = 134(1) GPa 1, and K1o = 2.0(3). Anisotropic compression was observed with unit strain axial ratios of 1:1.82:2.08. The CrO6 octahedron has a bulk modulus Ko = 90(16) GPa1, while the SiO4 tetrahedron has Ko = 313(55) GPa 1, both with K1o= 4. An o-type rotation of the O3-O3-03 linkage was observed with pressure, with
• Pommier, C. J., Denton, M. B., & Downs, R. T. (2003). Raman spectroscopic study of spodumene (LiAlSi₂O₆) through the pressure-induced phase change from C2/c to P2₁/c. Journal of Raman Spectroscopy, 34(10), 769-775.
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  Abstract: High-pressure Raman spectroscopy was used to follow the effects of a phase transition on the Raman spectrum of a natural specimen of the pyroxene spodumene, from its low-pressure (C2/c) to its high-pressure (P21/c) phases. The transition occurred at 3.2 GPa and was accompanied by an increase from 15 to 23 observed peaks, owing to a decrease in symmetry. Comparisons were made with other pyroxenes with the same space groups. The change in Raman shift with pressure of all peaks observed is reported. An additional change in the spectrum is observed between 7.7 and 8.9 GPa, possibly due to the formation of an additional bond between Li and O3 or some other transition that retained the mineral's P21/c space group. Splitting of the peak appearing at ∼700 cm-1, used to characterize the P21/c phase in other studies, was not observed. Copyright © 2003 John Wiley & Sons, Ltd.
• Prevatt, J., & Denton, M. B. (2003). Advances in the application of array detectors for improved chemical analysis, part II. Rapid trace metal analysis of high solids wastewater and sludge using a direct current plasma source equipped with an echelle spectrometer and a charge-injection device detector. Australian Journal of Chemistry, 56(2-3), 133-140.
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  Abstract: A direct current plasma (DCP) source, equipped with an echelle spectrometer and charge-injection device (CID) detector, was employed for the analysis of trace metals in municipal sludge and wastewater containing high solids. The use of DCP as a plasma source has largely vanished in the past decade due to the popularity of inductively coupled plasma. Resurrecting this robust plasma source and coupling it to a state-of-the-art echelle spectrometer provides for an extremely forgiving analytical technique capable of analysing trace metals rapidly, even in complex high-solid matrices. Instrument performance is further enhanced as the echelle/CID spectrometer provides a simultaneous multi-element fingerprint of contaminants in the waste. The improved design offers increased sensitivity in the far ultraviolet, with overall wavelength coverage from 175 to 800 nm. Furthermore, multi-element analysis is obtained quickly with minimal or no sample preparation, making this the fastest screening technique available.
• Gailer, J., Madden, S., Buttigieg, G. A., Denton, M. B., & Younis, H. S. (2002). Identification of [(GS)₂AsSe]^- in rabbit bile by size-exclusion chromatography and simultaneous multielement-specific detection by inductively coupled plasma atomic emission spectroscopy. Applied Organometallic Chemistry, 16(2), 72-75.
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  Abstract: An arsenic-selenium metabolite that exhibited the same arsenic and selenium X-ray absorption nearedge spectra as the synthetic seleno-bis(S-glutathionyl) arsinium ion [(GS)2AsSe]- was recently detected in rabbit bile within 25 min after intravenous injection of rabbits with sodium selenite and sodium arsenite. X-ray absorption spectroscopy did not (and cannot) conclusively identify the sulfur-donor in the in vivo sample. After similar treatment of rabbits, we analyzed the collected bile samples by size-exclusion chromatography (SEC) using inductively coupled plasma atomic emission spectroscopy (ICP-AES) to monitor arsenic, selenium and sulfur simultaneously. The bulk of arsenic and selenium eluted in a single peak, the intensity of which was greatly increased upon spiking of the bile samples with synthethic [(GS)2AsSe]-. Hence, we identify [(GS)2AsSe]- as the major metabolite in bile after exposure of rabbits to selenite and arsenite. The reported SEC-ICP-AES method is the first chromatographic procedure to identify this biochemically important metabolite in biological fluids and is thus a true alternative to X-ray absorption spectroscopy, which is not available to many chemists. Copyright © 2001 John Wiley & Sons, Ltd.
• H., J., Sperline, R., Denton, M. B., Barinaga, C. J., Koppenaal, D., Young, E. T., & Hieftje, G. M. (2002). Characterization of a focal plane camera fitted to a Mattauch-Herzog geometry mass spectrograph. 1. Use with a glow-discharge source. Analytical Chemistry, 74(20), 5327-5332.
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  PMID: 12403588;Abstract: A Mattauch-Herzog geometry mass spectrograph (MHMS) has been equipped with a novel array detector, the focal plane camera (FPC). The FPC consists of an array of gold Faraday cups, each coupled to its own integrator, with interrogation of the integrators performed by a multiplexer. The initial coupling of this instrument with a pintype glow discharge source has provided limits of detection in the single to hundreds of nanograms per gram regime; isotope ratio accuracy and precision better than 5% error and 0.2% RSD, respectively; and a linear dynamic range of at least 6 orders of magnitude. A current weakness of the FPC is its pixel size, which limits both sensitivity and baseline resolution (to R = 130). The minimum data acquisition time for multiple images at present is 1 ms/image, with a dead time of 3.2 ms between images, which will limit the ability of the FPC to monitor extremely short transient signals.
• Karczmarski, J. D., Miketova, P., Schram, K. H., Vytrasova, J., Cervenka, L., Pejchalova, M., Schram, K. H., Denton, M. B., & Moore, I. M. (2002). Detection of listeria sp. Using cell membrane profiles. Proceedings 50th ASMS Conference on Mass Spectrometry and Allied Topics, 581-582.
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  Abstract: The use of mass spectral ionization methods to study lipid membrane profiles for the detection of Listeria sp. was discussed. The lipid membrane profiles of various Listeria sp. were acquired using different mass spectrometry techniques in order to differentiate the pathogen, Listeria monocytogenes, from related non-pathogenic strains which included L. grayi, L. inanovii, L. seeligeri and L. welshimeri. It was observed that the patterns of unsaturation in the fatty acids chains were evident and species specific. The taxanomical differences were observed in the positive mode of ionization, while structural data was observed from positive mode of ionization.
• Knight, A. K., Sperline, R. P., Barnes, J. H., Barinaga, C. J., Young, E. T., Denton, M. B., Hieftje, G. M., & Koppenaal, D. W. (2002). Development of a micro-Faraday, focal plane array detector for mass spectrometry. Proceedings 50th ASMS Conference on Mass Spectrometry and Allied Topics, 879-880.
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  Abstract: A micro-Faraday based focal plane array detector was developed for mass spectrometric applications. Advanced multiplexer electronics for direct charge detection and versatile signal integration and readout were used for the development of the detector. The Faraday array was fabricated using conventional lithography technique. The detector was assembled with a Mattauch-Herzog geometry MS (MHMS) system and tested by operating them in both static and scanning modes. The results show that the resolution obtained in the static mode was about R∼150, which was improved by scanning to R∼300.
• Knight, A. K., Sperline, R. P., Hieftje, G. M., Young, E., Barinaga, C. J., Koppenaal, D. W., & Denton, M. B. (2002). The development of a micro-Faraday array for ion detection. International Journal of Mass Spectrometry, 215(1-3), 131-139.
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  Abstract: A micro-Faraday array detector was evaluated for use as an ion detector for mass spectrometry. This charge-integrating detector was based upon the merging of technologies from the fields of CCDs and infrared (IR) multiplexers. Measurements were performed by exposing the detector to an Ar+ ion beam of low flux. The array detector responds to both positive and negative charges and preliminary results indicate a detection limit of 100 ions. Current data indicate that the linear dynamic range of the device is over five orders of magnitude. The capability of the device to perform specialized charge read out modes could theoretically both lower the detection limit by a factor of seven and increase the linear dynamic range to nine orders of magnitude using non-destructive read outs. © 2002 Published by Elsevier Science B.V.
• Hieftje, G. M., Barnes, J. H., Grøn, O. A., Leach, A. M., McClenathan, D. M., Ray, S. J., Solyom, D. A., Wetzel, W. C., Denton, M. B., & Koppenaal, D. W. (2001). Evolution and revolution in instrumentation for plasma-source mass spectrometry. Pure and Applied Chemistry, 73(10), 1579-1588.
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  Abstract: Plasma-source mass spectrometry, usually in the form of inductively coupled plasma mass spectrometry (ICP-MS), has matured into a widely accepted method for ultra-trace multielemental analysis. However, the method exhibits shortcomings. For example, it does not provide adequate precision for isotope ratio measurements if many isotopes are to be determined. Moreover, isobaric overlaps (spectral interferences) can be very troublesome in some situations. Similarly, matrix interferences can adversely affect many determinations. Yet, it is in the area of high-speed transient measurements that ICP-MS perhaps suffers its greatest weakness. When sampling devices such as flow injection, laser ablation, electrothermal vaporization, or chromatography are employed, the user must choose between broad elemental or isotopic coverage and signal-to-noise ratio (S/N). In turn, compromised S/N means lower precision or poorer detection limits. Here, new instrumentation aimed at overcoming these limitations will be described. One system, based on a time-of-flight mass spectrometer, provides excellent detection limits, resolving power better than commercial quadrupole mass filters, precision of at least 0.02% rsd in a ratioing mode, and extraordinarily high speed for use with transient sampling devices. The second instrument is based on a sector-field mass spectrometer but, unlike other such units, is equipped with a focal-plane array detector. So equipped, the system can detect a broad mass range at once.
• Pennebaker, F. M., & Denton, M. B. (2001). High-precision, simultaneous analysis of Pt, Pd, and Rh in catalytic converter samples by carius tube dissolution and inductively coupled plasma atomic emission spectroscopy with charge-injection device detection. Applied Spectroscopy, 55(4), 504-509.
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  Abstract: A robust method of analysis that uses multichannel array detector technology is presented for high-precision, accurate measurement of Pt, Pd and Rh in catalytic converters. Catalytic converter samples, National Institute of Standards and Technology (NIST) reference standards, and a fresh converter sample are dissolved and analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Complete dissolution of sample sizes up to 2 g of NIST reference standards is achieved with the use of high-pressure, high-temperature carius tubes. Carius tube dissolution of a modern catalytic converter sample is found to be incomplete because of the presence of higher concentrations of Ce, Ni, and Zr. For this sample, the addition of FeCl3 increases the dissolving power of the carius tube for base metals and noble metals, particularly Rh. Although interference problems are encountered in samples bearing high concentrations of Fe, use of a high-resolution ICP-AES system alleviated these problems. Precise quantitation of Pt, Pd, and Rh is accomplished by using the method of standard additions, with high accuracy and a precision of 1-2% RSD (relative standard deviation). This analysis also confirmed the values determined by NIST by using isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) for standard reference materials (SRMs) 2556 and 2557.
• Pennebaker, F. M., & Denton, M. B. (2001). Precision and noise in inductively coupled plasma atomic emission spectroscopy with charge-injection device detection. Applied Spectroscopy, 55(6), 722-729.
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  Abstract: An inductively coupled plasma (ICP)-echelle optical system coupled with a charge-injection device (CID) detector was evaluated for precision and noise. Simultaneous collection of analyte wavelengths and simultaneous background correction have invalidated underlying assumptions in some traditional models. Signal flicker noise, a major limitation in single-channel detection, was eliminated by the time correlation of analyte and internal standard wavelengths. Once flicker noise was eliminated, most fluctuation was found to be caused by slight wavelength shifts along the axis of the detector, rather than by the theoretically predicted signal shot noise. This fluctuation can be corrected by increasing center subarray sizes or by employing well-matched internal standard lines. In either case, precision of 0.3 to 0.18% relative standard deviation (RSD) was achieved over a time span of 7 h. Background flicker noise was also eliminated by simultaneous background correction, demonstrating a multichannel advantage of ICP detection using charge-transfer devices. In this work, theoretical expressions were developed to incorporate major sources of noise based on the specific readout characteristics of an array detector. These expressions match experimental data extremely well for measurement of relative standard deviation in background (RSDB) and detection limits. These data have then been compared to the single-channel case, which describes photomultiplier tube (PMT) detection, as well as the theoretical limit dictated by background shot noise.
• Simon, R. E., Walton, L. K., Liang, Y., & Denton, M. B. (2001). Fluorescence quenching high-performance thin-layer chromatographic analysis utilizing a scientifically operated charge-coupled device detector. Analyst, 126(4), 446-450.
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  PMID: 11340976;Abstract: A scientifically operated charge-coupled device detector combined with fluorescence quenching high-performance thin-layer chromatographic plates was employed for the detection of organic compounds. The plates were excited with 254 nm light from a mercury lamp, and quantitative information was obtained from organic compounds that absorbed the optimum conditions for detection. The linear dynamic range, sensitivity, and reproducibility of the system were evaluted by quantitative analysis of famotidine, acetaminophen, caffeine, and acetylsalicylic acid. The detection limits of the system were found to be in the nanogram range.
• Gailer, J., George, G. N., Pickering, I. J., Madden, S., Prince, R. C., Yu, E. Y., Denton, M. B., Younis, H. S., & Aposhian, H. V. (2000). Structural basis of the antagonism between inorganic mercury and selenium in mammals. Chemical Research in Toxicology, 13(11), 1135-1142.
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  PMID: 11087435;Abstract: Mercuric chloride toxicity in mammals can be overcome by co-administration of sodium selenite. We report a study of the mutual detoxification product in rabbit plasma, and of a Hg-Se-S-containing species synthesized by addition of equimolar mercuric chloride and sodium selenite to aqueous, buffered glutathione. Chromatographic purification of this Hg-Se-S species and subsequent structural analysis by Se and Hg extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of four-coordinate Se and Hg entities separated by 2.61 Å. Hg and Se near-edge X-ray absorption spectroscopy of erythrocytes, plasma, and bile of rabbits that had been injected with solutions of sodium selenite and mercuric chloride showed that Hg and Se in plasma samples exhibited X-ray absorption spectra that were essentially identical to those of the synthetic Hg-Se-S species. Thus, the molecular detoxification product of sodium selenite and mercuric chloride in rabbits exhibits similarities to the synthetic Hg-Se-S species. The underlying molecular mechanism for the formation of the Hg-Se-S species is discussed.
• Gailer, J., Madden, S., Burke, M. F., Denton, M. B., & Aposhian, H. V. (2000). Simultaneous multielement-specific detection of a novel glutathione-arsenic-selenium ion [(GS)₂AsSe]^- by ICP AES after micellar size-exclusion chromatography. Applied Organometallic Chemistry, 14(7), 355-363.
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  Abstract: In order to confirm the solution structure of [(GS)2AsSe]- (GS = glutathione), we have investigated the retention behaviour of a [(GS)2AsSe]-/oxidized glutathione (GSSG) mixture on a Sephadex G-25 (SF) column with Tris buffers (0.1 mol dm-3, pH 8.0) containing various surfactants at concentrations above the critical micellar concentration (CMC): hexadecyltrimethlammonium bromide (HDTAB; 30, 40 and 50 mmol dm-3); dodecyltrimethylammonium bromide (DDTAB; 50 mmol dm-3); and sodium lauryl sulfate (SLS; 50 mmol dm-3). An inductively coupled plasma atomic emission spectrometer (ICP AES) provided simultaneous on-line detection of arsenic, selenium and sulfur in the column effluent. The chromatographic retention behaviour was used to investigate the association of both compounds with the positively charged micelles (HDTAB and DDTAB mobile phases). The relative strength of association with the micelles provided insight into the effective negative charge on [(GS)2AsSe]- and GSSG. The chromatograms obtained with 50 mmol dm-3 HDTAB indicated that two glutathione molecules are associated with the elution of an arsenic-selenium compound. Combined, these chromatographic data strongly support the spectroscopically derived solution structure of [(GS)2AsSe]-. Copyright (C) 2000 John Wiley and Sons, Ltd.
• Gailer, J., Madden, S., Cullen, W. R., & Denton, M. B. (1999). The separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid on the hamilton PRP-X100 anion-exchange column. Applied Organometallic Chemistry, 13(11), 837-843.
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  Abstract: In order to separate the potential arsenite metabolites methylarsonous acid and dimethylarsinous acid from arsenite, arsenate, methylarsonic acid and dimethylarsinic acid, the pH-dependent retention behaviour of all six arsenic compounds was studied on a Hamilton PRP-X100 anion-exchange column with 30 mM phosphate buffers (pH 5, 6, 7, 8 and 9) containing 20% (v/v) methanol as mobile phase and employing an inductively coupled plasma atomic emission spectrometer (ICP-AES) as the arsenic-specific detector. Baseline separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid was achieved with a 30 mmol dm-3 phosphate buffer (pH 5)-methanol mixture (80:20, v/v) in 25 min. Arsenite is not baseline-separated from dimethylarsinic acid under these conditions. Copyright ©1999 John Wiley & Sons, Ltd.
• Gailer, J., Madden, S., Denton, M. B., & Aposhian, H. V. (1999). Chemical characterization of a mercury-selenium detoxification compound. ACS Division of Environmental Chemistry, Preprints, 39(2), 216-217.
• Giles, J. H., Gilmore, D. A., & Denton, M. B. (1999). Quantitative analysis using Raman spectroscopy without spectral standardization. Journal of Raman Spectroscopy, 30(9), 767-771.
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  Abstract: Compared with other spectroscopic techniques, Raman spectroscopy has not generally been applied to problems of quantitative analysis, primarily because it is assumed that spectral irreproducibility due to source, sample or optical parameters requires standardization of the Raman signal. However, a custom-built Raman spectrometer with a 785 nm excitation source has yielded a spectral peak height reproducibility of 0.5% relative standard deviation. Quantitative studies of glucose in water, ethanol in water and p-xylene in m-xylene, described here, illustrate the linearity and precision of the Raman system. In order to estimate the linear dynamic range of the instrument, detection limits were determined for benzene in water and in CCl4, demonstrating a range from sub-ppm to 100% concentration. Specific factors affecting spectral reproducibility, and therefore quantitative results, are discussed. The quality of the results presented indicates that Raman spectroscopy should be a more common quantitative spectroscopic technique. Copyright © 1999 John Wiley & Sons, Ltd.
• Gresham, C. A., Gilmore, D. A., & Denton, M. B. (1999). Direct comparison of near-infrared absorbance spectroscopy with Raman scattering spectroscopy for the quantitative analysis of xylene isomer mixtures. Applied Spectroscopy, 53(10), 1177-1182.
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  Abstract: In order to overcome instrument problems associated with moving parts, such as optical misalignment and/or mechanical breakdown, we have developed two solid-state (no moving parts) spectrometers suitable for many industrial process monitoring applications. The first instrument utilizes near-infrared absorbance spectroscopy with a 1024-element platinum-silicide linear photodiode array detector, and the other employs Raman scattering spectroscopy with a 1024×1024 element charge-coupled device (CCD) detector. In order to demonstrate the utility of solid-state instrumentation for industrial process monitoring analysis, both instruments were used for the simultaneous quantitative analysis of individual components of xylene isomer mixtures. The xylene isomer mixture samples prepared for this study contained approximately 75-86, 0.6-5, and 0.1-14% w/v ortho-, meta-, and para-xylene, respectively, to reflect compositions of xylene raw materials used by specialty chemical manufacturers. Each spectroscopic system provides a means for fast (seconds), nondestructive data acquisition with no sample preparation. With the use of the chemometric data treatment of partial least-squares (PLS) regression, the absolute accuracies at 95% confidence for each isomer were found to be ±0.05, ±0.12, and ±0.09% w/v with near-infrared spectroscopy and ±0.08, ±0.04, and ±0.07% w/v with Raman spectroscopy for ortho-, meta-, and para-xylene, respectively.
• Liang, Y., Simon, R. E., & Denton, M. B. (1999). Utilization of a scientifically operated charge-coupled device detector for high-performance thin-layer chromatographic analysis of tetracyclines. Analyst, 124(11), 1577-1582.
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  PMID: 10746316;Abstract: A high-performance thin-layer chromatography (HPTLC) method using a scientifically operated charge-coupled device detector is described for the assay of tetracycline pharmaceutical products. Quantitative information can be obtained for all samples on a TLC plate within a few seconds. The separation efficiency and detection limits were determined on both normal phase and reverse phase TLC plates. Fluorescence detection mode offers higher sensitivity than fluorescence quenching mode. The dynamic range, sensitivity, accuracy and precision of the system were evaluated. Detection limits of the impurities are in the range of 0.1 to 0.5 ng or 0.3 to 1% of tetracycline, depending on the compound, with a recovery percentage over 85%. The existing impurities in tetracycline capsules were determined using both HPLC and HPTLC techniques. All of the impurities were below the regulation level.
• True, J. B., Williams, R. H., & Denton, M. B. (1999). On the implementation of multielement continuum source graphite furnace atomic absorption spectrometry utilizing an echelle/CID detection system. Applied Spectroscopy, 53(9), 1102-1110.
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  Abstract: A continuum source, multielement graphite furnace atomic absorption spectrometer was developed that employed a high-resolution echelle polychromator with charge-injection device (CID) detection. The detection system employed a new device, the CID 38, and camera control unit, the SCM5000E, providing unique new capabilities. A data acquisition and analysis scheme was developed for the prototype system, and the instrument demonstrated detection limits approaching that of commercial line source graphite furnace atomic absorption spectroscopy (GFAAS). However, the performance degrades in the ultraviolet due to decreasing source output.
• Liang, Y., Denton, M. B., & Bates, R. B. (1998). Stability studies of tetracycline in methanol solution. Journal of Chromatography A, 827(1), 45-55.
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  PMID: 9894344;Abstract: The stability of tetracycline in methanol solution was investigated by UV-visible spectroscopy, HPLC and TLC methods. After dissolution in methanol, tetracycline decomposed rapidly under the influence of light and atmospheric oxygen, forming more than fourteen different degradation products. None of the previously reported degradation products, such as the epi- and anhydro-compounds, were detected as the final degradation products. The molecular structures for eight of the compounds were suggested by their product-ion mass spectra. A degradation sequence was proposed for the reactions of tetracycline with methanol. A new HPLC-MS mobile phase was developed, which solved the clogging problem at the interface between the HPLC and MS chamber and enabled a high separation efficiency. Copyright (C) 1998 Elsevier Science B.V.
• Pennebaker, F. M., Jones, D. A., Gresham, C. A., Williams, R. H., Simon, R. E., Schappert, M. F., & Denton, M. B. (1998). Spectroscopic instrumentation in the 21st Century: Excitement at the horizon: Plenary lecture. Journal of Analytical Atomic Spectrometry, 13(9), 821-827.
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  Abstract: Recent developments in technology have suggested a promising future for plasma spectroscopy. New optical technologies, such as volume phase technology and unconventional optical systems, when coupled with new generations of optical detectors promise to provide powerful tools for plasma diagnostics or spectrochemical analysis. Next generation charge injection devices will provide both complete random access of individual detector sites and 'collective readout,' a new readout mode. Collective readout will promise faster readout and improved signal to noise ratios. A new generation of pro-amp per pixel array detectors with proper addressing architecture will allow random pixel readout and extreme resistance to blooming. These technological advances will yield new capabilities for not only current and future plasma sources, but also vintage sources such as the microwave-induced plasma, the direct current plasma, direct current arc and the direct current spark. Developments in software data processing techniques including neural networks and other chemometric techniques will allow present and future spectroscopists to extract useful diagnostic and chemical information from the almost overwhelming abundance of analytical data generated by the present and future generations of array detectors.
• Hanley, Q. S., Campbell, J. W., & Denton, M. B. (1997). Application of energy-resolved measurements to laue diffraction: Determination of unit-cell parameters, deconvolution of harmonics and assignment of systematic absences. Journal of Synchrotron Radiation, 4(4), 214-222.
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  PMID: 16699233;Abstract: The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 Å3. Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 ± 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 21 screw axes (h, k or l = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.
• Hanley, Q. S., Dunphy, D. R., & Denton, M. B. (1996). A foil-mask spectrometer for laue diffraction pattern imaging: Simultaneous position, intensity and energy. Journal of Synchrotron Radiation, 3(3), 101-111.
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  PMID: 16702667;Abstract: An X-ray spectrometer for simultaneous position, intensity and energy determinations suitable for Laue diffraction applications is described. The foil-mask spectrometer consists of a series of metal foils of varying composition and thickness which are used to modulate the energy distribution of an incident X-ray source. Three modes of operation are described: a high-resolution spectrometer for measurement of nearly monochromatic X-rays, an intensity discriminator for partitioning the intensity from a small number of spatially overlapped monochromatic X-ray sources, and a low-resolution spectrometer for polychromatic X-rays with broad spectral features. The first mode of operation is designed to allow the energy of monochromatic Laue reflections to be measured with a resolution suitable for determination of unit-cell parameters. The second mode of operation is designed to allow the intensity of each component in a spatial region containing overlapping orders or spatially overlapped reflections to be discriminated for use in refinements or space-group assignment. The third mode of operation is described for completeness. The theory behind each mode of operation is described. The energy resolution of the spectrometer improves with the square root of the intensity of the incident beam. It also increases linearly with the change in energy with respect to transmission efficiency of a particular foil. In theory, the resolution of the spectrometer can readily exceed 50 eV over a wide range of energies depending on the foils used and the incident X-ray photon flux. Determinations of the energies of Mo Kα and Cu Kα radiation using a first-generation ten-foil spectrometer gave values of 17.5 ± 0.1 and 8.08 ± 0.05 keV, respectively. Treatment of random error shows good correspondence with a Poisson model. The use of this spectrometer is demonstrated using a sample of tetraphenylphosphonium tetrachlorooxomolybdenum(V). Comparison of predicted and observed energies shows good agreement over a wide range of energies. The ratio of predicted to measured energy for the first 50 measurements was 0.9918 ± 0.0344. Up to three components of a position having harmonic overlap were separated. This work demonstrates the feasibility of using Laue diffraction to completely determine the crystal structure of a molecule without recourse to monochromatic methods.
• Hanley, Q. S., Earle, C. W., Pennebaker, F. M., Madden, S. P., & Denton, M. B. (1996). Charge-Transfer Devices in Analytical Instrumentation. Analytical Chemistry, 68(21), 661A-667A.
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  Abstract: CTDs are an attractive alternative to film, vidicons, photodiode arrays, and photomultiplier tubes.
• Liang, Y., Baker, M. E., Gilmore, D. A., & Denton, M. B. (1996). Evaluation of commercial silica-gel HPTLC plates for quantitative fluorescence analysis. Journal of Planar Chromatography - Modern TLC, 9(4), 247-253.
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  Abstract: Several commercially available high-performance thin-layer chromatographic (HPTLC) plates were evaluated for quantitative fluorescence imaging analysis using scientific charge-coupled device (CCD) detection. This investigation examined the effects on the observed background intensity as it relates to: the technique used for precleaning the plates, the fluorescence from the plate backing material, the presence of inhomogeneous fluorescence 'impurities', and the thickness of the glass backing material and silica layer. The sensitivity and linear dynamic range were found to be limited primarily by the intensity of the fluorescence background from the plate rather than by the detector or the excitation source. The results show that plate precleaning is a crucial step in providing for a correctable fluorescence background sufficient for obtaining reliable quantitative results. The influence of particle size on sensitivity was negligible compared with the florescence background from the plates. With plate precleaning, detection limits of approximately 100 fg were obtained for rhodamine 6G with an intraimage linear dynamic range of four orders of magnitude when utilizing scientific CCD fluorescence detection.
• Liang, Y., Baker, M. E., Yeager, B. T., & Denton, M. B. (1996). Quantitative Analysis of Aflatoxins by High-Performance Thin-Layer Chromatography Utilizing a Scientifically Operated Charge-Coupled Device Detector. Analytical Chemistry, 68(22), 3885-3891.
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  Abstract: The use of a scientifically operated charge-coupled device (CCD) for the detection and quantitation of aflatoxins on a high-performance thin-layer chromatographic (HPTLC) plate was investigated. A nebulizer-based sample application system was utilized to quantitatively transfer the sample onto the HPTLC plate without disturbing the sorbent layer. Fluorescence excitation of the aflatoxins was accomplished with an ultraviolet transilluminator, which caused the analytes of interest to emit in the blue-green portion of the visible spectrum. The dynamic range, sensitivity, accuracy, and precision of the system were evaluated. Detection limits of the aflatoxins were determined to be in the low picogram range. The existence of aflatoxins in peanut butter samples was analyzed both quantitatively and qualitatively by using multidimensional TLC. The capabilities of the system for performing real-time monitoring of the separation process were also investigated.
• Denton, M., & Gilmore, D. A. (1995). New detector technologies and their impact on Raman spectroscopy. Proceedings of SPIE - The International Society for Optical Engineering, 2388, 121-130.
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  Abstract: The latest generation of solid state detectors including Charged- Coupled Devices (CCD) and Charge-Injection Devices will be reviewed. Over the last several years, these detectors have contributed to major advances in Raman spectroscopy. Compact Raman systems using diode laser excitation, fiber-optic probes, and new generations of imaging spectrometers have been developed. New approaches for implementing very high throughput monochromators will be discussed, and their impact on the overall Raman system considered. Detection sensitivities obtained using these new optical geometries and array detector technologies are truly astounding. Even at an analyte concentration of a few ppm, a spectrum with several identifiable peaks can be obtained in a mater of seconds. This high sensitivity coupled with the ability of fiber optics to provide remote as well as in-situ sampling now make Raman a technique appropriate for many medical, environmental, and industrial applications. An overview of combining proper optical systems with currently available and soon to be introduced detectors will be presented. A variety of operating parameters for today's and tomorrow's arrays including readout noise, quantum efficiency, dark current, cosmic ray noise, and readout modes will be considered.
• Zumwalt, M. C., & Denton, M. B. (1995). Using high performance liquid chromatography to determine the C₆₀:C₇₀ ratio in fullerene soot: An undergraduate chemistry lab. Journal of Chemical Education, 72(10), 939-940.
• Denton, M. (1994). Ongoing revolution in optical spectroscopy. Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting, 8.
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  Abstract: Recent advances in the capabilities of state-of-the-art array detectors offer exciting new frontiers for exploration. The latest generation of solid state detector arrays, including charge coupled devices (CCDs), charge injection devices (CIDS), and new hybrid devices, are becoming available in a variety of formats. The impact of these detectors on a number of spectroscopic techniques will be discussed. Several applications for improved chemical analysis, including rapid scan, fluorescent and atomic spectroscopy, will be presented as applications to describe a variety of design and software considerations. In each case, the impact of the new capabilities will be demonstrated through examples of experimental system performance. Present and future trends in spectroscopic analysis will be considered.
• Wentink, R. F., Carbone, J., Aloisi, D. C., Gibson, W. M., MacDonald, C. A., Hanley, Q. E., Fields, R. E., & Denton, M. B. (1994). Charge injection device detectors for x-ray imaging. Proceedings of SPIE - The International Society for Optical Engineering, 2279, 380-387.
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  Abstract: Charge Injection Device (CID) array detectors are well suited for the direct imaging with x- ray and particle beams. In common with CCD detectors, CID arrays have been shown to have good spatial resolution and broad spectral response in the visible range. In addition, CID imagers offer unique architectural features which may be particularly applicable to x-ray and particle beams, including exceptionally large pixel charge capacity, non-destructive pixel readout, and random pixel addressibility. These can dramatically extend the dynamic range, eliminate blooming effects, allow monitoring and dynamic adaptation of application exposure in real-time, improve signal-to-noise by repeated readout and permit the readout of small pixel sub-arrays at exceptionally fast rates. In addition CIDs possess extremely good radiation tolerance. Preliminary results of x-ray measurements with CIDs are presented along with a discussion of potential applications utilizing their unique features.
• Earle, C. W., Baker, M. E., Denton, M. B., & Pomeroy, R. S. (1993). Imaging applications for chemical analysis utilizing charge coupled device array detectors. TrAC - Trends in Analytical Chemistry, 12(10), 395-403.
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  Abstract: Scientific charge transfer devices (CTDs) are rapidly becoming the detector of choice for optical chemical analysis. The high sensitivity and resolution of these detectors make them ideal for a wide range of chemical imaging applications. In this article we high-fight some of the current trends and future research directions of CTDs as imaging detectors for chemical analysis.
• Zumwalt, M. C., & Denton, M. B. (1993). Photoionization mass spectrometry of C₆₀ and C₇₀ with a vacuum ultraviolet hydrogen laser source. Applied Spectroscopy, 47(11), 1739-1741.
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  Abstract: A time-of-flight mass spectrum of the C60 and C70 fnllerenes with the use of a vacuum ultraviolet H2 laser photoionization source is presented. The photon energy is 7.8 eV, approximately 0.2 eV above the reported ion thresholds of both molecules. This relatively low excess energy is believed to be insufficient for fragmentation, as demonstrated by production of only parent ions. © 1993 Society for Applied Spectroscopy.
• Pomeroy, R. S., Baker, M. E., Radspinner, D. A., & Denton, M. B. (1992). Fluorescence imaging of latent fingerprints with a cooled charge-coupled-device detector. Proceedings of SPIE - The International Society for Optical Engineering, 1439, 60-65.
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  Abstract: Images of fluorescently tagged latent fingerprints were obtained using a low power source and a scientifically operated charge-coupled device (CCD) detector. The luminescence of the fingerprints is chemically enhanced with a fluorescent tag, orthophthalaldehyde. The orthophthalaldehyde undergoes a Schiff base reaction with phenyl ring containing amino acids to produce fluorescence emission at ≈446 nm under UV illumination. An inexpensive, portable, low power UV source was constructed utilizing two 4-watt UV fluorescent lamps and appropriate filters. In the past, the use of filtered lamp sources resulted in an appreciable loss in sensitivity compared to laser sources. Preliminary investigations into the use of a low power tungsten filament lamp source for the excitation of NBD chloride tagged fingerprint on paper were also conducted. Sensitive detection by way of a CCD eliminates the need for the use of expensive, high power laser sources in field instruments and provides a wide range of additional advantages over photographic film.
• Radspinner, D. A., Fields, R. E., Earle, C. W., & Denton, M. B. (1992). Revolutionary impact of today's array detector technology on chemical analysis. Proceedings of SPIE - The International Society for Optical Engineering, 1439, 2-14.
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  Abstract: State-of-the-art array detector technology is having a profound impact on numerous types of chemical analysis. The unique capabilities of these detectors create unprecedented opportunities in the various domains of high resolution, ultra sensitive optical spectroscopy. These array detectors, including charge coupled devices (CCDs) and charge injection devices (CIDs) have found successful application in molecular fluorescence, chemiluminescence, and atomic emission spectroscopies. The potential of these detectors for spatial and spectral imaging has been realized in a variety of applications including thin layer chromatography and flow cytometry. Applications of array detectors to these areas are discussed along with the inherently unique methods of operation such as random access integration, time delay integration, and flat fielding.
• Bilhorn, R. B., Pomeroy, R. S., & Denton, M. B. (1991). Chapter 4 The Future of Intelligent Spectrometers in Speciation by Atomic Emission Spectrometry. Journal of Chromatography Library, 48(C), 75-99.
• Denton, M. B. (1991). Applications of charge-coupled and charge-injection devices in analytical spectroscopy. Proceedings of SPIE - The International Society for Optical Engineering, 1447, 2-11.
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  Abstract: The latest generation of solid-state arrays, including charge-coupled devices and charge injection devices, holds great promise for revolutionizing spectrochemical methods of analysis. However, successful application of these new technologies will require more than substituting new detectors for old. Different optical system configurations and operational approaches are considered and their impact on a number of spectroscopic techniques are discussed. Specific examples for efficiently employing x-y array detectors, including aberration corrected holographic grating, crossed interferometric dispersive and echelle spectrometers, are discussed. Present and future trends for applying array detector technology to advanced spectroscopic analysis are considered.
• Pomeroy, R. S., Jalkian, R. D., & Denton, M. B. (1991). Spark spectroscopy using charge transfer devices. Analysis, automated systems, and imaging. Applied Spectroscopy, 45(7), 1120-1125.
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  Abstract: An atomic emission spectroscopic system utilizing a spark source for excitation has been developed. The instrument employs a custom echelle spectrometer and a charge injection device (CID) array detector system. This system simultaneously covers wavelengths from 200 to 450 nm with a resolution of 0.02 nm at 300 nm. Solids sample analyses of steels and aluminums were used to demonstrate this system's speed, sensitivity, and flexibility. Automated systems for rapid qualitative and semi-quantitative screening of these materials will also be discussed. Another spectroscopic system based on a commercial imaging spectrograph and a charge-coupled device (CCD) array detector has been used to obtain temporally resolved spectral images of single sparks discharges.
• Pomeroy, R. S., Kolczynski, J. D., & Denton, M. B. (1991). Information-based expert systems for atomic emission spectroscopy. Applied Spectroscopy, 45(7), 1111-1119.
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  Abstract: The development of the direct-current plasma echelle/CID spectroscopic system for atomic emission spectroscopy (AES) provides new alternatives for automated system control and data analysis. With this system, the concept of the 'intelligent' spectrometer becomes tangible. The echelle/CID system simultaneously gathers a wealth of spectral information over a wide spectral region. The mechanical stability of the system and the absence of moving parts give rise to reproducible wavelength assignment. The large amount of spectral information acquired has led to the development of information-based expert systems for AES: automated qualitative analysis, semi-quantitative analysis, and an 'on the fly' matrix-dependent line selection. These algorithms are effective in situations where there is a large variability among samples. The analytical power of these routines is heavily dependent on their utilization of the large database and the use of fundamental spectroscopic principles. Examples of the use of these algorithms in environmental monitoring, in the identification of chemical waste, in the analysis of geologic materials and steels, and in HPLC-AES are presented.
• Babis, J., Pilon, M. J., & Denton, M. (1990). Spatial distribution of vacuum ultraviolet radiation in an inductively coupled plasma. Applied Spectroscopy, 44(8), 1281-1289.
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  Abstract: Spatially resolved emission maps of an ICP as a function of torch design, power, and gas flow rate have been obtained for O, N, Cl, Br, and C in the vacuum ultraviolet with the use of an Abel inversion data reduction algorithm. Two coolant tube configurations were studied, one a standard strait coolant tube with a 'bell'-style collar, and a second with a 'T'-shaped sidearm tube. The studies show that the maximum emission intensities for Br and Cl occurred below the top of the coolant tube and that the N 149.28-nm emission cannot be observed for the bell collar configuration. The investigation of the T-tube configuration yielded useful information for all elements studied, with optimum observation heights ranging from 8 mm above the load coil for C at 165.70 nm to 20 mm above the load coil for O at 130.49 nm. In most cases, the maximum intensity is observed in the center of the discharge. Signal-to-noise studies indicate that the highest power practical with the minimum flow rate possible should be used for the analysis of the four nonmetals investigated.
• Bilhorn, R. B., & Denton, M. (1990). Wide dynamic range detection with a charge injection device (CID) for quantitative plasma emission spectroscopy. Applied Spectroscopy, 44(9), 1538-1546.
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  Abstract: The operation and performance of an analytical plasma emission spectrometer based on an echelle polychromator and a charge injection device (CID) two-dimensional multichannel array detector is described. Quantitative analysis methodology for measuring the intensity of emission lines over a wide dynamic range is presented. The procedure involves varying the integration time on the detector for each spectral line, based on the intensity of that line, in a process called random access integration (RAI). The factors that determine the maximum number of spectral lines that may be simultaneously observed are presented. With current CID technology these include the size of the array, the intensity of spectral lines at the focal plane, and the size of the subarrays used to record the line intensities. The sensitivity and dynamic range of the system equal those of emission spectrometers employing photomultiplier tubes, and the flexibility to use any spectral line, or group of lines, for a particular element provides unprecedented ability to perform simultaneous multielement trace analysis in complex mixtures. Background intensity in the vicinity of each spectral line is measured simultaneously, enabling precise spectral background corrections. The simultaneous availability of the information from the entire emission spectrum allows spectral features of diagnostic value such as argon, hydroxide, and carbon emission to be monitored, as well as spectral features due to the principal components of the sample matrix. Changes in analysis conditions or matrix composition can be detected because of the availability of this additional information, thereby increasing the reliability of the analytical results.
• Denton, M., Pilon, M. J., & Babis, J. S. (1990). Vacuum ultraviolet inductively coupled plasma spectroscopy for element-selective detection of nonmetals. Applied Spectroscopy, 44(6), 975-978.
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  Abstract: Use of an inductively coupled plasma for elemental analysis of many organic compounds has been limited by the inability to provide sensitive analysis for a variety of nonmetallic elements. Data presented in this manuscript demonstrate detection limits and working curves showing usable dynamic ranges for oxygen, nitrogen, chlorine, and bromine in the vacuum ultraviolet region. The use of inductively coupled plasma as an element-selective gas-chromatographic detector is also investigated.
• Miller, P. E., & Denton, M. B. (1990). A notch rejection quadrupole mass filter. International Journal of Mass Spectrometry and Ion Processes, 96(1), 17-26.
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  Abstract: The quadrupole mass filter can be implemented in one of several operational modes. The present work describes the theory, construction, and operation of a unique mass rejection mass filter. In contrast to previous frequency tuned mass rejection filters, the position of the present filter is shown to be easily tuned by adjustment of the amplitude of the r.f. potential used to excite the electrode structure. © 1990.
• Phillips, H. A., Denton, M., Rozsa, K., & Apai, P. (1990). Absorption and emission of copper radiation in a low and a high voltage internal anode hollow cathode discharge. Spectrochimica Acta Part B: Atomic Spectroscopy, 45(7), 621-631.
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  Abstract: The internal anode hollow cathode discharge (IAHCD) achieves positive current voltage behavior in a hollow cathode related construction by using the obstructed discharge phenomenon. A stronger current-voltage dependence is obtained by increasing the degree of obstruction or decreasing the fill gas pressure. Of the five noble gases He, Ne, Ar, Kr and Xe, Ne provides the highest intensity for the Cu I 324.7 nm emission in both a low and high voltage version of the IAHCD. The other four noble gases have increased Cu I 324.7 nm emission intensity relative to neon in the high voltage discharge. Atomic absorption measurements through the cathode bore indicate that at the pressure yielding the highest Cu I 324,7 nm emission for each gas and the same current for all investigated gases, the absorbance of the discharge increases with the atomic weight of the fill gas. The intensity of the Cu II 224.3 and 224.7 nm lines compared to the Cu I 324.7 nm line are greatest for Ar, Ne and He gases whose metastable or ion energies are greater or equal to the excitation energy of the ion lines. The ionic-atomic line intensity ratio is higher in the high voltage than the low voltage IAHCD. © 1990.
• Pilon, M. J., Denton, M., Schleicher, R. G., Moran, P. M., & Smith Jr., S. B. (1990). Evaluation of a new array detector atomic emission spectrometer for inductively coupled plasma atomic emission spectroscopy. Applied Spectroscopy, 44(10), 1613-1620.
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  Abstract: A unique echelle spectrometer system employing charge injection device (CID) array detector technology for use in inductively coupled plasma atomic emission spectroscopy (ICP-AES) is described. Due to improvements in optical design, this system offers increased wavelength coverage and improved light throughput over those of previous systems. Low sensitivity in the far-ultraviolet has been considered a major draw-back when silicon-based detectors are used, due to absorbance in the insulating SiO2 layer. The problem has been overcome through the use of a wavelength conversion phosphor. Therefore, detection limits comparable to those available with most commercial instruments have been obtained even in the far-UV. Operating parameters including precision, resolution, and background correction are also discussed. An analysis of the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1643b demonstrates that the system is capable of simultaneously determining at least 15 elements using 31 emission wavelengths with a high degree of accuracy.
• Pomeroy, R. S., Sweedler, J. V., & Denton, M. (1990). Charge-injection device detection for improved performance in atomic-emission spectroscopy. Talanta, 37(1), 15-21.
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  Abstract: Studies into the use of simultaneous multiwavelength detection over a broad wavelength region (220-520 nm) demonstrate the power and flexibility offered by a charge-injection device for detection in atomic-emission spectrometry. An echelle monochromator and a charge-injection device utilizing the general electric CID17B array detector are used in conjunction with a direct current plasma source to perform multi-line analysis for Mg, Sr, Fe, Dy, Ho and Yb, increasing the sensitivity and limits of detection. By monitoring the 341-nm OH band and background Ar emission lines, changes in the nebulization and excitation conditions are easily detected. The presence of an organic matrix component not present in the standards is detected by observing the C(I) emission at 247.8 nm. These diagnostic tools can be combined with the use of an internal standard to obtain a reliability not previously available in automated AES instrumentation. © 1987.
• Sims, G. R., & Denton, M. B. (1990). Simultaneous multielement atomic-emission spectrometry with a charge-injection device detector. Talanta, 37(1), 1-13.
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  Abstract: Simultaneous multielement atomic-emission spectrometry with a charge-inection device (CID) as a multichannel optical detector is described. The system used in this study employs a standard commercial D.C. plasma source, a modified echelle spectrometer, and a special digital camera system that uses a two-dimensional CID array sensor. A description of the modified spectrometer is given along with performance results. Computer algorithms for acquiring and analysing spectral information are described. Detection limits for several elements are determined simultaneously. Results of simultaneous determination of several elements in an NBS standard reference material (SRM 1643A) are given. These results indicate that the CID detector is capable of reasonably good accuracy and high sensitivity in the simultaneous determination of several elements in complex samples. © 1987.
• Smith, T. R., & Denton, M. B. (1990). Evaluation of current nebulizers and nebulizer characterization techniques. Applied Spectroscopy, 44(1), 21-24.
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  Abstract: The operating characteristics of a number of recent, commercially available inductively coupled plasma (ICP) nebulizer designs have been compared. The operating characteristics studied included bulk efficiency, primary and tertiary aerosol production, and analyte response by ICP-AES. Several concentric glass nebulizers along with a slurry and a dual-platinum-grid nebulizer were investigated. In all cases, tertiary aerosol production was found to be the best indicator of the analytical performance of the nebulizer. Of the nebulizers studied, the dual-platinum-grid nebulizer was found to generate the largest quantity of aerosol and to possess the most compatible droplet-size distribution for use with an ICP.
• Sweedler, J. V., Jalkian, R. D., Sims, G. R., & Denton, M. B. (1990). Crossed interferometric dispersive spectroscopy. Applied Spectroscopy, 44(1), 14-20.
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  Abstract: A novel design is described which combines dispersive and interferometric spectrometric instrumentation for ultraviolet visible spectroscopy, offering significant advantages in comparison to conventional spectroscopic configurations. The optical system incorporates the triangular common-path interferometer with an additional cross-dispersive element, allowing spectra to be obtained in a format compatible with rectangular CTD array detectors. The use of a cross-dispersive optical element reduces the distributive multiplex effects of interferometry in a rugged, compact, optically simple system.
• Babis, J. S., Kacsir, J. M., & Denton, M. B. (1989). Glass capillary array nebulizer for atomic spectrometry. Applied Spectroscopy, 43(5), 786-790.
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  Abstract: The nebulization of sample solution is a critical step in most atomic spectrometric methods. A novel nebulization technique, based on a glass capillary array, has been investigated. Basic operating parameters and characteristics have been studied to determine how this new nebulizer may be applied to atomic spectrometric methods. The results of preliminary comparisons with current pneumatic nebulizers as well as the porous glass frit nebulizer indicate several notable differences. The glass capillary array nebulizer has a high sample transport efficiency, and, in addition, the glass capillary array is not as limited in performance as the porous frit nebulizer in terms of sample equilibration time and the requirement for a wash cycle. The nebulizer shows great promise where sample volume is limited or where rapid response is necessary, as in chromatography or flow injection analysis.
• Bilhorn, R. B., & Denton, M. B. (1989). Elemental analysis with a plasma emission echelle spectrometer employing a charge injection device (CID) detector. Applied Spectroscopy, 43(1), 1-11.
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  Abstract: An atomic emission spectrometer which allows simultaneous high-precision digital recording of the ultraviolet spectrum has been developed. The instrument employs both a custom-built echelle spectrometer and a custom-built slow-scan charge injection device (CID) based detector system. The system is capable of measuring the wide dynamic range of signal intensities associated with plasma emission sources, and sensitivity is comparable to that of photomultiplier-tube-equipped instruments. Unprecedented speed and flexibility for elemental analysis are provided by the ability to display background-subtracted emission spectra and to have the computer assist in spectral line identification.
• Epperson, P. M., & Denton, M. B. (1989). Binning spectral images in a charge-coupled device. Analytical Chemistry, 61(14), 1513-1517.
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  Abstract: A charge-coupled device (CCD) can selectively combine photogenerated charge from several detector elements into a single charge packet via a special charge readout mode called binning. This article focuses on the use of charge binning in a two-dimensional CCD for Increasing the sensitivity and dynamic range of spectroscopic measurements. Binning allows the effective detector element size to be matched to the size of the silt image. Equations describing the signal-to-noise ratio and dynamic range of the binned readout of spectral lines are developed. Results of binning to increase the sensitivity of atomic emission and molecular fluorescence measurements are presented. An lntraspectral dynamic range of 500 000 is achieved by mixing binned and normal readout modes of a Hg atomic emission spectrum. Practical factors related to binning spectral Images including spectral line orientation, readout speed, and blooming are discussed. © 1989 American Chemical Society.
• Epperson, P. M., Jalkian, R. D., & Denton, M. B. (1989). Molecular fluorescence measurements with a charge-coupled device detector. Analytical Chemistry, 61(3), 282-285.
• Kolczynski, J. D., Pomeroy, R. S., Jalkian, R. D., & Denton, M. B. (1989). Spatial and spectral imaging of plasma excitation sources. Applied Spectroscopy, 43(5), 887-891.
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  Abstract: The imaging polychromator used in this study has been shown to have good flat-field response and no observable coma or astigmatism. In addition, it is simple and rugged. The polychromator is also the first commercially available instrument specifically designed to be interfaced with both linear and area array detectors. With the coupling of these two technologies, the rapid and sensitive detection afforded by the CCD detectors, along with the computer-aided data manipulation, provides an advantage in image array processing. Although the resolution of this polychromator system limits its application in atomic emission spectroscopy, the resolution is acceptable for molecular fluorescence and UV-Vis absorption spectroscopy. The spatial fidelity of the system can be used in multidimensional luminescence or to monitor several sources with a single polychromator.
• Phillips, H. A., Smith, T. R., Webb, B. D., & Denton, M. B. (1989). Simplified construction of demountable ICP torches. Applied Spectroscopy, 43(8), 1488-1489.
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  Abstract: Demountable ICP torch bases make possible the rapid and inexpensive replacement of the portions of the torch glassware which become opaque, fused closed, or broken. A description is given of two recent torch base designs: a one-piece base and a two-piece base. Both bases reduce the cost of ICP operation by allowing the easy replacement of any damaged quartz. The one-piece base is small enough to fit into a commercial system. Use of the two-piece base allows the positions of the sample and plasma tubes to be changed relative to each other and relative to the load coil during plasma operation. The one- and two-piece demountable torch bases are relatively simple to construct and allow increased flexibility in the operation of the ICP.
• Pomeroy, R. S., Denton, M. B., & Armstrong, N. R. (1989). Voltammetry at the thin-film mercury electrode (TFME): Anodic and cathodic stripping voltammetries and simple potentiostat construction. Journal of Chemical Education, 66(10), 877-880.
• Pomeroy, R. S., Kolczynski, J. D., Sweedler, J. V., & Denton, M. (1989). Analysis of microgram amounts of particulate material by simultaneous multiwavelength AES. Mikrochimica Acta, 99(3-6), 347-353.
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  Abstract: A unique simultaneous emission spectrograph is utilized to perform qualitative and quantitative analysis on trace quantities of solid particulates. The atomic emission spectroscopic system consists of a direct current plasma source and an echelle spectrograph with a charge injection device detector, enabling the system to simultaneously measure the wavelength range from 220 nm to 520 nm with 0.02 nm resolution at 300 nm. Monitoring all wavelengths simultaneously allows the qualitative and quantitative determination of most major and minor constituent in a trace quantity of sample with little prior knowledge about the sample. The ability to perform qualitative and quantitative analysis on particulates is demonstrated by evaluating NBS certified coal fly ash, as well as a sample taken from the respirator air filter at an acute care unit in a hospital. © 1990 Springer-Verlag.
• Smith, T. R., & Denton, M. B. (1989). LTE conditions within the cental channel of the plasma. Applied Spectroscopy, 43(8), 1385-1387.
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  Abstract: Studies were performed on the effect of torch pressure on the excitation conditions within an inductively coupled plasma (ICP). Experimentally measured magnesium ion-to-atom ratios and electron densities were used to determine the deviation of the plasma from local thermodynamic equilibrium (LTE) conditions. Results of these studies indicate that the plasma is in an infrathermal state when operated at atmospheric pressure, and excitation conditions within the central channel of an ICP shift towards LTE conditions as torch pressure is increased.
• Sweedler, J. V., & Denton, M. B. (1989). Spatially encoded Fourier transform spectroscopy in the ultraviolet to near-infrared. Applied Spectroscopy, 43(8), 1378-1384.
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  Abstract: A spatial (Sagnac triangular common path) interferometer is described and evaluated for obtaining spectra in the 200-950 nm wavelength region. The interferometer has no moving parts, requires no entrance or exit slits, and is easy to align. A linear CCD is employed as the detector, allowing spectra to be simultaneously acquired. The performance of the interferometer is demonstrated for atomic emission and solution absorbance spectra. A method to remove the fixed-pattern response of the detector and optical system is demonstrated which effectively increases the dynamic range of the resulting spectra.
• Sweedler, J. V., Jalkian, R. D., & Denton, M. (1989). Linear charge-coupled device detector system for spectroscopy. Applied Spectroscopy, 43(6), 953-962.
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  Abstract: The spectroscopically important performance capabilities of a linear charge-coupled device detector system, along with the methods used to evaluate the detector performance, are described. The linearity, read noise, full-well capacity, charge transfer efficiency, and ultraviolet to near-infrared quantum efficiency of the detector are presented along with the methods required to operate the detector in unconventional modes allowing low noise and antiblooming operation. With the antiblooming mode of operation, the detector performance is shown to be unaffected by light overloads hundreds of times over the saturation level. The performance of the detector for high-resolution diagnostic studies of hollow cathode lamps as well as for molecular fluorescence is presented.
• Sweedler, J. V., Jalkian, R. D., Pomeroy, R. S., & Denton, M. (1989). A comparison of CCD and CID detection for atomic emission spectroscopy. Spectrochimica Acta Part B: Atomic Spectroscopy, 44(7), 683-692.
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  Abstract: The performances of two classes of charge transfer device detectors-the charge-coupled device and the charge injection device-are compared for atomic emission spectroscopy. For these studies, a direct current plasma source is employed with an echelle spectrograph having a spectral image size matched to the format of these array detectors. In a clean matrix, both detectors yield good detection limits. In more complex matrices, blooming, or the spilling of excess photogenerated charge from the regions of the detector which are overexposed, greatly limits the utility and sensitivity of the charge-coupled device for atomic emission spectroscopy. Several methods to improve the performance of charge-coupled device detectors are described, including preliminary work using an antiblooming charge-coupled device. The charge injection device detector is found to be highly resistant to blooming and is able to analyze complex mixtures with little to no loss in sensitivity. © 1989.
• Epperson, P. M., Sweedler, J. V., Bilhorn, R. B., Sims, G. R., & Denton, M. B. (1988). Applications of charge transfer devices in spectroscopy. Analytical Chemistry, 60(5), 327 A-335 A.
• Jalkian, R. D., & Benton, M. (1988). Ultra-trace-level determination of cobalt, chromium, and hydrogen peroxide by luminol chemiluminescence detected with a charge-coupled device. Applied Spectroscopy, 42(7), 1194-1199.
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  Abstract: A solid-state two-dimensional charge-coupled device (CCD) is used to detect the chemiluminescence of luminol with hydrogen peroxide and a transition metal ion. The chemiluminescence spectra are recorded with the use of trace amounts of metal ions. Excellent linearity, dynamic range, and detection limits are obtained for the total amount of Cr3+, CO2+, and H2O2 analyzed by manual injection. Detection limits on the order of low femto-mole levels of analytes are reported. The utility of CCDs for ultra-low-level light measurements is discussed, and new concepts for 'luminometers,' both wavelength dispersive and nondispersive, are described.
• Phillips, H. A., Lancaster, H. L., Denton, M., Rozsa, K., & Apai, P. (1988). SELF-ABSORPTION IN COPPER HOLLOW CATHODE DISCHARGES: EFFECTS ON SPECTRAL LINE SHAPE AND ABSORPTION SENSITIVITY.. Applied Spectroscopy, 42(4), 572-576.
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  Abstract: The intensity of the hyperfine doublet of the Cu(I) 324. 8-nm transition was observed as a function of current, fill gas, and fill gas pressure for a new design of hollow cathode lamp incorporating a positive column and an enlarged volume cathode cavity. The intensity ratio of the two components, which reflects the degree of self-absorption, and the flame absorption sensitivity were compared with those of a conventional hollow cathode lamp. Higher intensity, better component ratio, and increased absorption sensitivity were found in the new lamp.
• Bilhorn, R. B., Epperson, P. M., Sweedler, J. V., & Denton, M. B. (1987). SPECTROCHEMICAL MEASUREMENTS WITH MULTICHANNEL INTEGRATING DETECTORS.. Applied Spectroscopy, 41(7), 1125-1136.
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  Abstract: This article covers three major topics related to the optimum use of integrating detectors in analytical spectroscopy. The advantages of employing integrating multichannel detectors in analytical spectroscopy, rather than a single detector in a wavelength scanning system or an interferometer, are discussed. Included are detector read noise considerations. When one is employing an integrating detector in luminescence, absorption, and emission applications, achievable sensitivity is dependent on differing detector parameters.
• Bilhorn, R. B., Sweedler, J. V., Epperson, P. M., & Denton, M. B. (1987). CHARGE TRANSFER DEVICE DETECTORS FOR ANALYTICAL OPTICAL SPECTROSCOPY - OPERATION AND CHARACTERISTICS.. Applied Spectroscopy, 41(7), 1114-1125.
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  Abstract: In this paper, charge transfer devices (CTDs) are described. Detector characteristics pertinent to spectroscopic application - including quantum efficiency, read noise, dark count rate, and available formats - are emphasized. Unique capabilities, such as the ability to nondestructively read out the detector array and the ability to alter the effective detector element size by a process called binning, are described. CTDs with peak quantum efficiencies over 80% and significant responsivity over the wavelength range of 0. 1 nm to 1100 nm are discussed.
• Denton, M. B. (1987). Concepts for improved automated laboratory productivity. Plenary lecture. The Analyst, 112(4), 347-353.
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  Abstract: The use of automated laboratory techniques is rapidly increasing. Significant changes are occurring both in how tasks are accomplished and in which tasks are practical and cost effective. Although the automation of a given task does not inherently dictate the use of some form of computer, the greater system flexibility achieved through software control, coupled with the recent drastic reduction in computer hardware costs, has already made this approach to automation extremely popular. The vast proliferation of computational hardware does not solve all of the problems in laboratory automation-far from it. Two major problem areas arise, development of suitable function systems to conduct the desired chemistry and development of the proper software. Today, in many instances workers have resorted to mimicking human manipulation of samples through the use of robotics. Although this approach is viable for some situations, it is far from optimal for many other applications. Laboratory automation today often involves the use of instruments designed to perform a specific task (e.g., sample preparation and analysis) on a high work load. However, there is a trend toward increasing flexibility through multi-task capability. This concept can be implemented through several means. One example would be an instrument which is configured in such a manner that it can or does obtain a wide range of data. Software quickly sifts through the results and displays the requested information to the user. This approach allows a great deal of flexibility, as different information can be obtained merely by changing the software. Additionally, the presence of possible interferences, unusual results on species not requested and even over-all system performance can be constantly monitored and presented to the user. Many of these concepts will be considered while describing a new generation of intelligent atomic spectrometric instrumentation. The ultimate goal is an automated system capable of accepting any type of sample and performing any analysis such that all desired information would be obtained. Ideally, following analysis, the sample would be returned unharmed. Such a highly flexible, non-destructive instrument is "science fiction" today, but much more limited systems based on present technology are not out of the question.
• Epperson, P. M., Sweedler, J. V., Denton, M., Sims, G. R., McCurnin, T. W., & Aikens, R. S. (1987). ELECTRO-OPTICAL CHARACTERIZATION OF THE TEKTRONIX TK512M-011 CHARGE-COUPLED DEVICE.. Optical Engineering, 26(8), 715-724.
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  Abstract: The electro-optical characterization of the first in a new series of Tektronix CCDs is described. This device, the TK512M-011, is a frontside-illuminated CCD with a 512 by 512 format and 27 by 27 mu m pixels. Electro-optical characteristics measured in this study include linearity, blooming, dark count rate, charge-transfer efficiency (CTE), and quantum efficiency. The results of a detailed study of the noise characteristics of the CCD output FET are reported. The TK512M-011 has excellent photometric linearity, high well capacity, and a low dark count rate. Very good low light level CTE is observed in the parallel shift direction; however, CTE problems are observed in the serial direction. The quantum efficiency of the front-side-illuminated CCD over the wavelength range of 400 to 1000 nm is lower than expected based on experience with similar devices. The noise of the output FET of the CCD is equivalent to 5 to 12 electrons, depending on the FET operating conditions and system bandwidth.
• Huth, T. C., & Denton, M. B. (1987). Analysis of complex mixtures by photoionization mass spectrometry with a vacuum-ultraviolet hydrogen-laser source. Analytica Chimica Acta, 192(C), 165-173.
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  Abstract: Trace organic analysis of a complex matrix presents one of the most challenging problems in analytical mass spectrometry. Inselective electron-impact ionization often requires extensive sample clean-up to isolate the analyte from the matrix. Sample preparation can be greatly reduced when a hydrogen laser is used for selective photoionization of only a small fraction of the compounds introduced into the ion source. This device produces parent ions only for all compounds with ionization potentials that lie below a threshold value limited by the photon energy of 7.8 eV. The only observed interference arises from electron-impact ionization when scattered laser radiation interacts with metal surfaces, producing electrons which are then accelerated by potential fields inside the source. These can be suppressed to levels acceptable for practical analysis through proper instrumental design. Results are presented which indicate the ability of this ion source to discriminate against interfering matrix components in simple extracts from real samples such as brewed coffee, beer, and urine. © 1987.
• Sims, G. R., & Denton, M. (1987). CHARACTERIZATION OF A CHARGE-INJECTION-DEVICE CAMERA SYSTEM AS A MULTICHANNEL SPECTROSCOPIC DETECTOR.. Optical Engineering, 26(10), 1008-1019.
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  Abstract: A solid-state camera system designed for use as a multichannel detection system for spectroscopic applications is evaluated. The camera is based on a charge-injection-device sensor that permits very high dynamic range operation by virtue of its unique nondestructive readout capability. Methods of determining gain and readout noise are discussed. Performance of the camera system is evaluated with respect to sensitivity, linearity, readout noise, and dynamic range. The use of nondestructive readout to reduce effective readout noise and increase dynamic range is described. Spectral responses in the visible and ultraviolet of coronene-coated and uncoated devices are reported. Various time-dependent anomalies caused by interface trapped charge are discussed.
• Sims, G. R., & Denton, M. (1987). SPATIAL PIXEL CROSSTALK IN A CHARGE-INJECTION DEVICE.. Optical Engineering, 26(10), 999-1007.
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  Abstract: An optical multichannel detector system based on a charge-injection device (CID) sensor has been designed and constructed. This system is intended for use in a variety of spectroscopic studies, including atomic emission spectrometry (AES), in the ultraviolet to near-infrared spectral region. A General Electric Co. CID11B was selected as the sensor because preliminary research indicated that this device has excellent characteristics for detection of the very wide dynamic range signals encountered in AES. During initial characterization of this detection system, a phenomenon was observed in which the signal obtained from reading a pixel of the array was affected by the quantity of charge in orthogonally located pixels. Investigations indicate that this spatial crosstalk effect is not caused by charge migration among pixels ('blooming') as in many other types of imaging detectors.
• Smith, T. R., & Denton, M. (1987). HIGH-PRESSURE INDUCTIVELY COUPLED PLASMA TORCH.. Applied Spectroscopy, 41(4), 654-657.
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  Abstract: An inductively coupled plasma (ICP) torch utilizing an extended coolant tube that tapers down to a small exit orifice designed to increase the pressure within the ICP torch is described. This torch design makes use of the advantages associated with higher torch operating pressures (including improved detection limits, increased sensitivity, and better plasma stability), without requiring major modifications to existing commercially available ICP torch box and matching networks. Detection limits obtained with the use of the new torch design are compared with those obtained from several commonly used torch designs using a commercially available torch box and spectrometer.
• Smith, T. R., Phillips, H. A., & Denton, M. (1987). SAFETY SHUTOFF FOR YOUR PLASMA TORCH BOX.. Applied Spectroscopy, 41(2), 330-.
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  Abstract: The authors present a simple circuit that can be added to most commercial ICP-AES systems that will automatically shut off the rf power if the plasma is extinguished. This circuit design has been used on at least four ICPs in the authors' laboratory for the past three years and has proven to be an invaluable safeguard. The theory of operation is discussed. The entire sensor circuit will easily fit in a 1 5/8 in. multiplied by 2 1/8 in. multiplied by 2 3/4 in. Model Cu-3000-a BUD box and can be mounted on the side of the commercial torch box. The parts list is included in this study.
• Sweedler, J. V., Denton, M., Sims, G. R., & Aikens, R. S. (1987). SINGLE-ELEMENT CHARGE-INJECTION DEVICE AS A SPECTROSCOPIC DETECTOR.. Optical Engineering, 26(10), 1020-1028.
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  Abstract: The need for a single-element charge-transfer device as a spectroscopic detector is discussed. Such a detector promises to offer superior performance compared to current photomultiplier tubes over a wide range of illumination levels. As a detector to address this need, the prototype CID75 manufactured by General Electric Co. is described and characterized. The CID75 is a single-element charge-injection-device sensor with a 1 mm by 1 mm photoactive area and a readout rate adjustable from 0 to 20 kHz. The electro-optical characteristics reported in this study include linearity, read noise, full-well capacity, dark count rate, and quantum efficiency. The sensors have good photometric linearity with a full-well capacity in excess of 1. 2 multiplied by 10**8 e** minus . The read noise of the detector can be lowered to 80 e** minus when its nondestructive readout mode is employed. The quantum efficiency of the CID75 is reported for the wavelength range from 200 to 1000 nm.
• Webb, B. D., & Denton, M. B. (1987). Effect of torch size on a 148-MHz inductively coupled plasma. Journal of Analytical Atomic Spectrometry, 2(1), 21-26.
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  Abstract: Physical parameters and analytical performance are presented for three analytical ICPs operated at 148 MHz. The torch size has been varied in these three systems in order to investigate more closely the influence of the ratio of plasma radius (r) to skin depth (s) on the plasma characteristics. The electron number density appears to be directly related to the r/s ratio, while the excitation temperatures and ion to atom intensity ratios only follow a general trend. A10 mm i.d. torch at 148 MHz provides conditions most similar to a standard 18 mm i.d. torch at 27 MHz. An intermediate-size torch of 13 mm i.d. provides a good balance between the increased ease of sample handling of a large r/s ratio torch and the improved sensitivity of a small r/s ratio system. The r/s ratio is shown to be a convenient means of understanding the effects of changes in the plasma operating frequency and in the torch size.
• Miller, P. E., & Denton, M. (1986). The transmission properties of an RF-only quadrupole mass filter. International Journal of Mass Spectrometry and Ion Processes, 72(3), 223-238.
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  Abstract: The performance of a quadrupole mass filter operated in the RF-only mode was investigated. Data are presented which demonstrate that the transmission properties of such devices deviate markedly from that which would be predicted from the Mathieu stability diagram. Discussion of the factors influencing the transmission efficiency of ions through an RF-only quadrupole is presented. The transmission efficiency of ionic species through an RF-only quadrupole is primarily influenced by three factors. The first of these is the formal stability of the ion trajectory as summarized by the coordinates of the particle in a, q space. The second factor is the acceptance aperture of the quadrupole in combination with the emittance of the ion source. The final factor is shown to be spatial focusing conditions which arise due to the nature of the frequency components that are contained within the trajectory of an ion as it traverses the quadrupole electrode structure. The theory of such spatial focusing conditions is reported. The measurement of naturally occurring isotope abundance ratios is used to demonstrate the magnitude of errors which may result due to the non-ideal transmission properties of the RF-only quadrupole. Suggestions are provided to minimize such mass discrimination effects. © 1986.
• Miller, P. E., & Denton, M. B. (1986). The quadrupole mass filter: Basic operating concepts. Journal of Chemical Education, 63(7), 617-622.
• Webb, B. D., & Denton, M. (1986). Comparison of a very high frequency 148 MHz inductively coupled plasma to a 27 MHz ICP. Spectrochimica Acta Part B: Atomic Spectroscopy, 41(4), 361-376.
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  Abstract: Physical parameters and analytical performance are determined for an analytical ICP operated at 148 MHz, a frequency nearly three times higher than any previously reported. The iron(I) excitation temperatures are approximately 1.5 times lower and the electron densities are five times lower than at 27 MHz. The consequences of these changes are lower analyte and background continuum emission intensities, such that the signal to background ratios are decreased at the higher frequency. Freedom from interferences and working curve linearity are unaffected while ease of sample introduction is improved. A shift towards atomic emission indicates a deviation farther from LTE at 148 MHz. These effects are attributed to the decrease in skin depth with increasing frequency. © 1986.
• Algeo, J. D., Heine, D. R., Phillips, H. A., Hoek, F. B., Schneider, M. R., Freelin, J. M., & Denton, M. B. (1985). On the direct determination of metals in lubricating oils by ICP. Spectrochimica Acta Part B: Atomic Spectroscopy, 40(10-12), 1447-1456.
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  Abstract: New equipment and procedures are evaluated for the direct analysis of metals in lubricating oils without the need for sample pretreatment or dilution. A modified Babington principle nebulizer equipped with a sample heater is shown to be capable of producing aerosols from undiluted oils, which are suitable for introduction into an inductively coupled plasma atomic emission spectrophotometer. Heating the samples immediately prior to nebulization greatly increases the output of aerosol and reduces output variations in emission intensity due to differences in oil manufacture and viscosity. The type of organometallic complex used in the preparation of standards is shown to be unimportant if the plasma observation region is properly chosen. Performance of a conventional plasma geometry and an inverted torch geometry on analysis of field collected oil samples is presented. © 1985.
• Babis, J. S., Huth, T. C., & Denton, M. B. (1985). Construction techniques of a molecular hydrogen laser. Review of Scientific Instruments, 56(10), 1969-1970.
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  Abstract: Simple techniques are described for construction of a discharge channel, and spark gap trigger electrode for a traveling-wave excited molecular hydrogen laser.
• Huth, T. C., & Denton, M. (1985). Photoionization mass spectrometry with a vacuum ultraviolet hydrogen laser source. International Journal of Mass Spectrometry and Ion Processes, 67(2), 199-208.
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  Abstract: Results are presented which characterize the vacuum ultraviolet H2 laser as a selective ion source for analytical mass spectrometry of easily ionized compounds. The types of compounds ionized below the photon energy of 7.8 eV include many pharmaceuticals and drugs of abuse, such as cocaine, heroin, phencyclidine, methamphetamine, and LSD. Hydrogen laser photoionization has produced parent ions only, for all compounds studied thus far. The selectivity of the threshold photoionization process is very high, as compounds within as little as 0.2 eV above the threshold are completely rejected. Photoactive species can be injected as solutions in appropriate organic solvents, without interference from the solvent. At low levels, ion signals are observed, which are due to acceleration of stray electrons in the ion source. The electrons result from interaction of scattered laser radiation with metal surfaces. © 1985.
• Smith, T. R., & Denton, M. (1985). On the operation of inductively coupled plasmas as a function of pressure. Spectrochimica Acta Part B: Atomic Spectroscopy, 40(9), 1227-1237.
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  Abstract: The effect of pressure on the operating conditions within a 27-MHz inductively coupled plasma is investigated. The results show a direct relationship between torch pressure and the excitation temperature of an analyte species introduced into the plasma. The excitation temperature of the plasma support gas is shown to increase with torch pressure. A shift towards local thermal equilibrium is also observed with increasing pressure. The possibility of using alternate plasma support gases such as He is also investigated. © 1985.
• Tilden, S. B., & Denton, M. (1985). COMPARISON OF DATA REDUCTION TECHNIQUES FOR LINE-EXCITED OPTOACOUSTIC ANALYSIS OF MIXTURES.. Applied Spectroscopy, 39(6), 1017-1022.
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  Abstract: The use of discrete line laser excitation for the optoacoustic analysis of gas mixtures holds promise as a formidable analytical tool. However, this technique presents challenging demands on the data reduction process to increase the reliability of the analytical results. The problems unique to this method which make data reduction difficult are discussed. Use of simultaneous equations, multivariate least-squares, and a new iterative coefficient weighted least-squares approach are compared. Data indicating the relative performance of these methods are presented.
• Tilden, S. B., & Denton, M. (1985). THEORY AND EVALUATION OF A WINDOWLESS NONRESONANT OPTOACOUSTIC CELL.. Applied Spectroscopy, 1022-1029.
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  Abstract: A novel nonresonant flow-through optoacoustic cell is characterized. This cell is operated without windows, completely eliminating the window background interference. Data are presented comparing sensitivity, resistance to cross-contamination, and operating characteristics of this approach with more conventional single and differential cell techniques. The capability of operation at widely varying sample flow rates is demonstrated.
• Aikens, R. S., Epperson, P. M., & Denton, M. (1984). TECHNIQUES FOR OPERATING CHARGE COUPLED DEVICES (CCD's) IN VERY HIGH SPEED FRAMING MODE.. Proceedings of SPIE - The International Society for Optical Engineering, 501, 49-54.
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  Abstract: New concepts for operating charge coupled devices (CCD's) in a multiple frame transfer mode which allow very high speed imaging of transient phenomena are described. These methods coupled with the inherent advantages of slow scan readout, including high dynamic range, low noise and excellent linearity, provide unique, new observational capabilities. Appropriate masking techniques allow a large portion of the CCD to be employed as a high speed image buffer. Applications include spatial imaging of rapidly moving objects, observations of transient spectral chemical phenomena and the study of rapid physiological motion.
• Algeo, J. D., & Denton, M. B. (1982). A comparison of three methods for the determination of wear metals in lubricating oils: direct introduction-ICP, solvent dilution-AAS, and ashing-AAS.. Array.
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  Abstract: A new method for the analysis of wear metals in lubricating oils which utilizes a modified Babington Principle nebulizer was compared to two other existing methods. The new method was found to be faster and more convenient than the others. When compared to the results from an existing solvent dilution method, the results from the new method showed a stronger correlation to those of the reference method.
• Heine, D. R., Denton, M. B., & Schlabach, T. D. (1982). Determination of nucleotides by liquid chromatography with a phosphorus-sensitive inductively coupled plasma detector. Analytical Chemistry, 54(1), 81-84.
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  Abstract: Quantitative analysis of 100-μL nucleotide samples is accurately performed by analyzing total phosphorus concentration using an inductively coupled plasma (ICP) system. A single calibration using Na2HP04(aq) is useful for all nucleotides. A detection limit of 750 ng of phosphorus is determined with a relative standard deviation of 4.5%. High-performance liquid chromatography (HPLC) is used to separate mixtures of nucleotides on an anton exchange column using acetate buffers. The ICP is used as a selective detector by observing P I emissions at 213.6 nm. A Babington nebulizer which is used to aspirate the high percentage salt solutions with 6% efficiency is described. © 1981 American Chemical Society.
• Koontz, S. L., & Denton, M. B. (1982). VERY HIGH YIELD ELECTRON IMPACT ION SOURCE FOR ANALYTICAL MASS SPECTROMETRY.. Annual Conference on Mass Spectrometry and Allied Topics, 527-528.
• Algeo, J. D., & Denton, M. B. (1981). ON THE USE OF THE INVERTED ABEL INTEGRAL FOR EVALUATING SPECTROSCOPIC SOURCES.. Applied Spectroscopy, 35(1), 35-42.
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  Abstract: A numerical method for evaluating the inverted Abel integral employing cubic spline approximations is described along with a modification of the procedure of Cremers and Birkebak, and an extension of the Barr method. The accuracy of the computations is evaluated at several noise levels and with varying resolution of the input data. The cubic spline method is found to be useful only at very low noise levels, but capable of providing good results with small data sets. The Barr method is computationally the simplest, and is adequate when large data sets are available. For noisy data, the method of C. J. Cremers and R. C. Birkebak gave the best results.
• Brown Jr., R. M., Fry, R. C., Moyers, J. L., Northway, S. J., Denton, M. B., & Wilson, G. S. (1981). INTERFERENCE BY VOLATILE NITROGEN OXIDES AND TRANSITION-METAL CATALYSIS IN THE PRECONCENTRATION OF ARSENIC AND SELENIUM AS HYDRIDES.. Analytical Chemistry, 53(11), 1560-1566.
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  Abstract: When tested individually in a clean system, NO//3** minus and HNO//3 are shown not to be serious inhibitors of AsH//3 and H//2Se evolution. The real inhibitors of AsH//3 and H//2Se evolution (encountered when solid samples are oxidatively dissolved in nitric acid) are shown to be correspondingly reduced nitrogen oxides (NO//2** minus , etc. ) produced in sample digestion. Volatile NO//x interferants can then result upon acidic disproportionation. These volatile NO//x species are found to transport with the AsH//3 and H//2Se analyte. The N//2O//3 species is detected in a cryogenic trap.
• Koontz, S. L., & Denton, M. (1981). A very high yield electron impact ion source for analytical mass spectrometry. International Journal of Mass Spectrometry and Ion Physics, 37(2), 227-239.
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  Abstract: A novel ion source designed for use in mass spectrometric determination of organic compounds is described. The source is designed around a low pressure, large volume, hot cathode Penning discharge. The source operates in the 10-4 -10-7 torr pressure domain and is capable of producing focusable current densities several orders of magnitude greater than those produced by conventional "Nier"-type sources. Mass spectra of n-butane and octafluoro-2-butene are presented. An improved signal-to-noise ratio is demonstrated with a General Electric Monopole 300 mass spectrometer. © 1981.
• Reinsfelder, R. E., & Denton, M. (1981). Theory and characterization of a separator analyzer mass spectrometer. International Journal of Mass Spectrometry and Ion Physics, 37(2), 241-250.
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  Abstract: A separator analyzer mass spectrometer (SAMS) technique is described. The approach utilizes sequential tandem quadrupole structures. The first quadrupole, operated in the notch filter mode, is used to reject one or more masses of ions. The theory of operation and the performance observed are described. © 1981.
• Fry, R. C., & Denton, M. B. (1979). CHARACTERISTICS OF A ″HIGH SOLIDS″ NEBULIZER FOR FLAME ATOMIC ABSORPTION SPECTROMETRY.. Applied Spectroscopy, 33(4), 393-399.
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  Abstract: Studies are presented to characterize a new nebulizer developed for direct atomic absorption analysis of extremely complex clinical and environmental materials. Important parameters are described concerning the design and performance of ″high solids″ spectrochemical nebulizers based on the Babington principle. A new simplified design is presented and mechanisms of undesirable sample wastage are considered. Data are presented concerning the effect of impaction on conventional and ″high solids″ aerosol generation.
• Fry, R. C., & Denton, M. B. (1979). MOLECULAR ABSORPTION SPECTRA OF COMPLEX MATRICES IN PREMIXED FLAMES.. Anal Chem, 51(2), 266-268.
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  Abstract: The question of molecular spectral interferences by undissociated inorganic matrix salts is inevitably raised when the direct atomic absorption analysis of digested or untreated complex materials is considered. Data presented in these studies indicate that the problem is not nearly as serious for premixed flame systems as has been reported for electrothermal and total consumption burner atomization.
• Fry, R. C., Denton, M. B., Windsor, D. L., & Northway, S. J. (1979). HYDRIDE PRECONCENTRATION FOR INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROMETRY.. Applied Spectroscopy, 33(4), 399-404.
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  Abstract: Studies are presented describing an improved application of the NaBH//4 reduction of soluble arsenite to form arsine as a preconcentration approach for ultra-trace level arsenic determination by inductively coupled plasma optical emission spectrometry. Specialized analyte introduction techniques are described for elimination of reaction by-products that would normally extinguish a medium power plasma discharge. An approach is presented to minimize the need for background correction and facilitate a superior arsenic detection limit in a relatively inexpensive 1. 2 kW inductively coupled plasma system.
• Windsor, D. L., & Denton, M. (1979). ELEMENTAL ANALYSIS OF GAS CHROMATOGRAPHIC EFFLUENTS WITH AN INDUCTIVELY COUPLED PLASMA.. Journal of Chromatographic Science, 17(9), 492-496.
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  Abstract: The performance of the inductively-coupled plasma (ICP) as an element selective gas chromatographic (GC) detector is investigated. Special emphasis is placed on evaluating the ability of the ICP to perform simultaneous, multielement analyses on each component of a mixture. In general, ICP detection limits, linear dynamic ranges, and selectivities are shown to compare favorably with those which have been observed for the flame photometric detectors (FPD), argon, and low pressure helium microwave-excited plasma detectors (MEPD).
• Windsor, D. L., & Denton, M. B. (1979). Empirical formula determination with an inductively coupled plasma gas chromatographic detector. Analytical Chemistry, 51(8), 1116-1119.
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  Abstract: The ability of the inductively-coupled plasma (ICP) gas chromatographic (GC) detector to determine empirical formulas is evaluated. Elemental compositions and empirical formulas of hydrocarbons and halogens are determined as the compounds are eluted from a chromatograph. The observed accuracy and precision are found to be of sufficient quality to indicate that the technique holds promise for the determination of empirical formulas. © 1979 American Chemical Society.
• Windsor, D. L., & Denton, M. (1978). EVALUATION OF INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROMETRY AS A METHOD FOR THE ELEMENTAL ANALYSIS OF ORGANIC COMPOUNDS.. Applied Spectroscopy, 32(4), 366-371.
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  Abstract: The application of inductively coupled plasma optical emission spectrometry (ICP-OES) to the elemental analysis of organic compounds is evaluated successfully for seven nonmetallic elements. A comparison of this method with previously reported microwave techniques shows that, while both methods are sensitive (detection limits in the low nanogram region), ICP-OES has fewer complications and appears to be less prone to interferences than the analogous microwave techniques. The results of these studies suggest that ICP-OES should be applicable to the simultaneous multielement analysis of the gaseous effluents from a gas chromatograph.
• Denton, M. B. (1977). Performance of the super modified simplex. Analytical Chemistry, 49(9), 1422-1428.
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  Abstract: A new, improved simplex optimization procedure has been developed which significantly increases the utility, reliability, and efficiency of current state-of-the-art simpllcial methods in the presence of random response fluctuations. Comparison of this improved procedure, the Super Modified Simplex (SMS), with several variations of the modified simplex approach utilizing an interactively computer-controlled flame spectrephotometer reveals Its Inherent superiority In rapidly and efficiently conforming to multidimensional response surface topography. Data are presented which Indicate fewer simplices and data points, as well as a reduction in experimental time results when the SMS procedure is employed. Moreover, failure to satisfactorily locate the optimum in the presence of noise due to premature diminuation of the simplex, adherence to false ridges, or inability to accurately home in on the optimum is minimized.
• Fry, R. C., & Denton, M. B. (1977). HIGH SOLIDS SAMPLE INTRODUCTION FOR FLAME ATOMIC ABSORPTION ANALYSIS.. Analytical Chemistry, 49(9), 1413-1417.
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  Abstract: Studies are presented describing direct, clog-free production of high density finely dispersed aerosols from highly complex samples through use of a special nebulizer design based on principles first developed by R. S. Babington. Application of this technique to sample introduction for atomic absorption spectrometry is described for matrices of combined high suspended solids content, increased viscosity, and elevated salt concentration. Cu and Zn are determined in whole blood, urine, seawater, evaporated milk concentrate, and tomato sauce with minimal sample preparation.
• Routh, M. W., & Denton, M. B. (1976). EVALUATION OF THE CONTRIBUTION OF ORGANIC SOLVENT SPECIES TOWARD SIGNAL ENHANCEMENT IN THE PREMIXED OXYGEN-HYDROGEN FLAME.. Applied Spectroscopy, 30(3), 344-349.
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  Abstract: Studies conducted in premixed oxygen-hydrogen, oxygen-acetylene, and nitrous oxide-acetylene flames utilizing a relatively small drop size aerosol generated with high frequency ultrasonic nebulization indicate that under the proper conditions emission signal enhancements observed with methanol can be attributed primarily to both increased rate of nebulization and the presence of additional reducing species. However, under the fuel-rich conditions commonly employed for analysis, solvent-supplied reducing species were found to be of primary significance only in the case of the premixed oxygen-hydrogen flame.
• Suddendorf, R. F., Gutzler, D. E., & Denton, M. B. (1976). On the utilization of pulse ultrasonic nebulization for analyzing small volumes of solution by flame emission spectrometry. Spectrochimica Acta Part B: Atomic Spectroscopy, 31(5), 281-287.
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  Abstract: A pulse ultrasonic nebulizer system capable of reproducibly introducing small sample volumes into a flame for analysis by flame emission spectrometry i. © 1976.
• Eckhardt, J., Denton, M., & Moyers, J. L. (1975). SULFUR FPD FLOW OPTIMIZATION AND RESPONSE NORMALIZATION WITH A VARIABLE EXPONENTIAL FUNCTION DEVICE.. Journal of Chromatographic Science, 13(3), 133-138.
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  Abstract: Description of the optimum flow characteristics of the flame photometric sulfur detector to maximize both the relative sensitivity and the exponential proportionality factor ( ″n″ ). In this investigation it was found that the gas flow rates for hydrogen and nitrogen plus oxidant as well as the oxidant to fuel ratio drastically affect both the exponential proportionality factor and the relative sensitivity. Also described is a simple, inexpensive electronic device designed to monitor the output signal of a flame photometric sulfur detector. With this device it is possible to obtain a linear response with changing sulfur concentration even in cases where the photomultiplier output current is proportional to the sulfur concentration raised to a power of less than two.
• Gutzler, D. E., & Denton, M. B. (1975). Improvements in flame emission spectrometry through the use of ultrasonic nebulization into a premixed oxygen-hydrogen flame. Analytical Chemistry, 47(6), 830-833.
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  Abstract: A laminar flow premixed oxygen-hydrogen flame when combined with ultrasonic nebulization has demonstrated substantial improvements in detection limits for a number of elements studied when compared to those obtained using laminar nitrous oxide-acetylene, laminar oxygen-acetylene, and a conventional turbulent oxygen-hydrogen flame. The improved performance observed is attributed to the low flame background emission and reduced flame flicker.
• Denton, M. B., & Swartz, D. B. (1974). An improved ultrasonic nebulizer system for the generation of high density aerosol dispersions. Review of Scientific Instruments, 45(1), 81-83.
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  Abstract: An ultrasonic nebulizer system capable of converting solution into an aerosol of various controlled droplet sizes with conversion rates in excess of 1 ml/min is described. This design allows generation of various sizes of droplets through overtone operation and simplified transducer substitution. The described irradiation cell is constructed from glass and fluorocarbon materials providing a high degree of chemical inertness.
• Suddendorft, R. F., & Denton, M. B. (1974). BURNING PARAMETERS OF PREMIXED OXYGEN-HYDROGEN AND OXYGEN-ACETYLENE FLAMES.. Applied Spectroscopy, 28(1), 8-13.
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  Abstract: Parameters affecting the stability of premixed oxyhydrogen and oxyacetylene flames are investigated. The results of this study show the effect of port diameter, fuel-oxidant ratio, total gas flow, and burner temperature on the stability of these flames. Data were obtained by the use of a specially designed and constructed one-hole insert burner. The results of this study provide the required design criteria and operational parameters for utilization of these fuel mixtures.
• Korte, N. E., Moyers, J. L., & Denton, M. B. (1973). Investigations into the use of a pulse ultrasonic nebulizer-burner system for atomic absorption spectrometry. Analytical Chemistry, 45(3), 530-534.
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  Abstract: An integral pulse ultrasonic nebulizer-burner system is described which combines the desirable characteristics of flame atomization with an ultrasonic nebulizer system capable of reproducibly nebulizing small volumes of solution. Data are presented comparing this sytem with a conventional pneumatic slot burner system, showing improved sensitivity and a reduction in the required sample volume.
• Smith, R. G., Bryan, R. J., Denton, M. B., Feldstein, M., Levadie, B., Locke, D. C., Miller, F. A., Stephens, E. R., & Warner, P. O. (1973). Tentative method of analysis for phenols in the atmosphere (gas chromatographic method). Health Laboratory Science, 10(4), 362-366.
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  PMID: 4752048;
• Stanley, J. L., Bentley, H. W., & Denton, M. B. (1973). Radiation exposure considerations when employing microwave excited spectroscopic sources. Applied Spectroscopy, 27(4), 265-267.
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  Abstract: Studies are described which demonstrate the presence of microwave radiation levels exceeding the present national safety standards in the vicinity of several common microwave excited source configurations. Since the various pathological effects of microwave energy are not fully understood, shielding considerations and on site radiation surveys are recommended.
• Swartz, D. B., Denton, M. B., & Moyers, J. L. (1973). On calibrating of cascade impactors. American Industrial Hygiene Association Journal, 34(10), 429-439.
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  PMID: 4766098;Abstract: This paper presents a detailed coverage of the relevant considerations pertaining to the calibration of cascade impactors. A simple and inexpensive method utilizing a polydisperse wax aerosol is described. In the method an aerosol is generated by the condensation of wax vapor. The size distribution of the aerosol is controlled by the flow rate of a carrier gas stream. Microscopic counting and sizing procedures are detailed. Various methods for evaluating impactor performance characteristics are reviewed and discussed. Calibration data using this method are presented for a commercially available impactor and for a specially constructed cascade impactor.
• Denton, M. B. (1972). Burner and ultrasonic nebulizer improvements for atomic absorption spectrometry. Analytical Chemistry, 44(2), 241-247.
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  Abstract: An approach to optimized burner design for use with conventional commercial ultrasonic transducers is presented. Several burner designs are described that operate properly at very low flow rates so as to increase droplet residence time in the flame and minimize flow rate demands on the ultrasonic nebulizer. This system provides improved stability and an increase in sensitivity by atomic absorption of ten times compared with a conventional burner-pneumatic nebulizer system. The ultrasonic nebulization system is constructed for efficient introduction and changing of sample solutions.
• Denton, M. B., & Malmstadt, H. V. (1972). Ultrasonic nebulization in a low-emission flame for atomic fluorescence spectrometry. Analytical Chemistry, 44(11), 1813-1818.
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  Abstract: The use of an ultrasonic nebulizer in conjunction with a low turbulence, argon-hydrogen-entrained air flame provides improved performance of almost two orders of magnitude as compared with a conventional pneumatic total consumption burner. Increased sensitivity results from more efficient nebulization, reduced light scattering, and lower flame background emission. An automated sample changing system is described which provides the required freedom from sample cross-contamination.
• Iracki, E. S., Denton, M. B., & Malmstadt, H. V. (1972). Triac switching circuitry for eliminating interfering transients in digital logic automated systems. Analytical Chemistry, 44(11), 1924-1925.
• Denton, M. B., & Malmstadt, H. V. (1971). Tunable organic dye laser as an excitation source for atomic-flame fluorescence spectroscopy. Applied Physics Letters, 18(11), 485-487.
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  Abstract: A laser-pumped tunable organic dye laser is shown to excite atomic-flame fluorescence of the 5535. 5-Å barium resonance line. Ultrasonic nebulization reduces light scattering, producing a straight-line analytical working curve suitable for quantitative analysis. © 1971 The American Institute of Physics.

Presentations

• Denton, M. B. (2016, April). Advanced Instrumentation for Improved Chemical Analysis. University of North Texas, Denton, Texas. Denton, Texas: University of North Texas.
• Denton, M. B. (2016, January). 49 Years of Atomic Spectroscopy -- From Nebulizers to Detectors -- Time Marches On. 2016 Winter Conference on Plasma Spectrochemistry. Tucson, Arizona: Winter Conference on Plasma Spectrochemistry.
• Denton, M. B. (2016, Summer). Advanced Array Detectors for Optical and Mass Spectrometries. American Chemical Society 2016 Fall Meeting. Philadelphia, PA: Analytical Division of the American Chemical Society.
• Denton, M. B. (2014, January). Advanced Technology to Outwit the Terrorist and A Chemist Builds and Races a High Speed Sports Car - Or, What Could Go Wrong Here?. Eastman Chemical Company. Kingsport, TN.
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  Invited Presentation
• Denton, M. B. (2014, January). Advances in Instrumentation Contribute to Improved Chemical Analysis. Eastman Chemical Company. Kingsport, TN.
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  Invited Presentation
• Denton, M. B. (2014, January). Characterization of a New High Performance CMOS Array and Echelle Spectrometer for Atomic Emission Spectroscopy. 2014 Winter Conference on Spectrochemistry. Amelia Island, FL.
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• Denton, M. B. (2014, June). New Array Detectors for Mass Spectrometry. Pacific Northwest National Laboratory 2014 Mass Spectrometry Workshop. Richland, WA.
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  Invited Presentation
• Denton, M. B. (2013, March). Chemical Instrumentation - New Methodologies Open Doors for Advanced Handheld Instrumentation - Taking the Lab to the Sample. Pittsburgh Conference (Pittcon).
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• Denton, M. B. (2012, February). The Role of Raman Spectroscopy in Gem Identification and How Evolving Technology is Expanding its Use and Availability. Accredited Gemologists Association.
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  Invited Presentation
• Denton, M. B. (2012, January). High Resolution Plasma Instrumentation and Advanced Plasma Detectors. 2012 Winter Conference on Plasma Spectrochemistry.
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  Invited Presentation
• Denton, M. B. (2012, June). Recent Technological Advances Unleash the Analytical Power of an 80 Year Old Spectroscopic Technique - Raman Technology. Alchema 2012.
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  Invited Presentation

Others

• Denton, M. B. (2018, July). Brief of Amicus Curiae, State v. Mcphaul. Supreme Court of North Carolina.
• Denton, M. B. (2018, October). Brief of Amicus Curiae, Long v. Hooks. United States Court of Appeals for the Fourth Circuit.