University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Gary M. Hieftje

Abbrev:
Hieftje, G.M.
Other Names:
Address:
Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
Phone:
+1-812-855-2189
Fax:
+1-812-855-0958

Citations 12

"Determination Of Arsenic By Hydride Generation Coupled To Time-of-flight Mass Spectrometry With A Gas Sampling Glow Discharge"
Spectrochim. Acta B 2002 Volume 57, Issue 6 Pages 1009-1023
William C. Wetzel, José A. C. Broekaert and Gary M. Hieftje

Abstract: Hydride generation has been used with a gas-sampling glow discharge (GSGD) and time-of-flight mass spectrometry (TOFMS) for the determination of arsenic in solution. Helium, neon, hydrogen, and argon glow discharges have been successfully generated and characterized. Current-pressure-voltage curves were generated for each discharge in the presence and absence of hydride generation. The arsenic detection limit for each of the discharges was found to be 0.60 (HeGSGD), 3.8 (NeGSGD) and 6.4 ppb (H(2)GSGD). The HeGSGD was found to be the most attractive source for arsenic determination due to the lower detection limit, higher sensitivity and greater stability. The figures of merit for these discharges were also compared to those obtained with hydride generation-inductively coupled plasma TOFMS. Noise power spectra obtained for the neon GSGD indicated that no discernible discrete-frequency (whistle-noise) components were present in the analyte signal. (C) 2002 Elsevier Science B.V. All rights reserved.
Speciation Optimization

"Analytical Capabilities Of An Inductively Coupled Plasma Mattauch-Herzog Mass Spectrometer"
Spectrochim. Acta B 2001 Volume 56, Issue 9 Pages 1717-1729
David A. Solyom, Ole A. Gron, James H. Barnes IV and Gary M. Hieftje

Abstract: An inductively coupled plasma (ICP) has been coupled to a custom-designed Mattauch-Herzog mass spectrometer, replacing a glow-discharge source used in earlier research. Adaptation to an ICP source required significant modifications to address concerns regarding shielding from RF radiation and coupling between the ICP and mass spectrometer. The detrimental impact of fringing magnetic fields on the earlier performance of the instruments detector has also been addressed. Current figures of merit utilizing ultrasonic nebulization include sensitivities in the 108-109 cps ppm-1 isotope-1 regime and detection limits of 1-500 pg/l (ppq). Isotope-ratio accuracy and precision are 1% relative error and 1-2% relative standard deviation, respectively. Resolving power (5% valley) exceeds 400. Unfortunately, spectral peak shapes are somewhat disappointing and lead to abundance sensitivity values in the 103-104 range. Although the instrument is designed for use with a multichannel array detector, all results reported here were obtained in scanning mode to separate limitations of the spectrometer from those of the detector.

"Gas-sampling Glow Discharge Coupled To Hydride Generation For The Atomic-spectrometric Determination Of Arsenic"
Spectrochim. Acta B 1993 Volume 48, Issue 10 Pages 1207-1220
J. A. C. Broekaert, R. Pereiro, T. K. Starn and G. M. Hieftje

Abstract: A continuous-flow hydride generation system is described for use in the AES determination of As in solution, using 5% NaBH4, 5% NaOH and 2 M HCl as reagent and He, Ne or Ar as carrier gas. The product gas sampling rate was controlled to maintain a sampling efficiency of >75%. The gas was passed to a silica capillary attached to the cathode of a gas-sampling glow-discharge source, which was operated at constant voltage and pressure. Spatially resolved maps were obtained of the As I 228.8 nm line, the spectral background and the fill-gas lines, all as a function of the discharge pressure. Under optimized conditions the noise amplitude spectra of analytical signals were completely white. The detection limits of As with He (at 6.5 Torr, 650 V and 165 mA), Ne (at 2.5 Torr, 750 V and ~160 mA) and Ar (at 1.5 Torr, 550 V and ~165 mA) were 54, 30 and 20 ng/ml, respectively. The calibration graphs were rectilinear up to 10 µg/ml in the Ar discharge and up to 2.5 µg/ml in Ne and He.
Arsenic Spectrophotometry Optimization

"Flow Injection Analysis Utilizing A Spectrally Segmented Photodiode-array Inductively Coupled Plasma Emission Spectrometer. 1. Micro-column Preconcentration For Determination Of Molybdenum"
Spectrochim. Acta B 1989 Volume 44, Issue 4 Pages 349-358
N. Furuta, K. R. Brushwyler and G. M. Hieftje*

Abstract: The flow injection pre-concentration. of Mo for ICP-AES was achieved by adsorption from sample solution of pH 2 to 4 (5 mL min-1) on to a column (5 cm x 1.5 mm) of activated alumina pre-acidified by treatment with 0.01 M HNO3. The adsorbed molybdate was eluted with aqueous 2 M NH3 and fed directly to a Leco Plasmarray spectrometer having three dispersion gratings for photodiode-array detection at 287.15, 281.62 and 277.54 nm (spectral orders 198, 202 and 205, respectively; channel range 140 to 340). The calibration graphs for pre-concentration. times of 1 and 10 min were rectilinear up to 1 and 0.1 µg mL-1, respectively, and the detection limit (pre-concentration. for 10 min) was ~0.2 ng mL-1. The coefficient of variation (n = 10) were 1.95 to 2.17% and 4.5 to 5.55% for 500 and 10 ng mL-1, respectively, with pre-concentration. for 1 and 10 min. Up to 3% of NaCl did not interfere. Use of the photodiode array permitted detection of and correction for a background shift (caused by the injection of NH3) that occurred during the signal integration period.
Molybdenum Spectrophotometry Preconcentration Interferences Activated alumina

"Use Of Rapid Gas-flow Modulation For Improved Performance In Inductively Coupled Plasma Time-of-flight Mass Spectrometry"
J. Anal. At. Spectrom. 2005 Volume 20, Issue 12 Pages 1318-1325
Denise M. McClenathan and Gary M. Hieftje

Abstract: Modulation of the central-channel gas flow rate is explored as a means to operate the ICP as a switched source in order to achieve optimal performance for a greater range of elements and to alleviate certain isobaric overlaps. By rapidly switching between low and high central-channel flow rates, hot and cold plasma conditions are produced in an alternating fashion. Limits of detection with this modulation strategy are similar to those obtained under steady-state hot and cold plasma conditions. Because both plasma conditions are produced in a single analysis, this modulation technique should be particularly useful for multielemental analyzes that employ transient sampling methods such as chromatography, flow injection, electrothermal vaporization, and laser ablation. © The Royal Society of Chemistry 2005.

"Novel Flow Injection Strategies For Study And Control Of Matrix Interferences By Inductively Coupled Plasma Time-of-flight Mass Spectrometry"
J. Anal. At. Spectrom. 2001 Volume 16, Issue 9 Pages 987-990
Denise M. McClenathan, Steven J. Ray and Gary M. Hieftje

Abstract: Inductively coupled plasma time-of-flight mass spectrometry is ideally suited for use with flow injection because of its virtually simultaneous multi-elemental and multi-isotope capabilities. Here, novel flow injection strategies are employed for characterizing matrix interferences, as a diagnostic tool for detecting interferences and as a method for calculating the dilution factors necessary to overcome interferences. Gradient dilution flow injection allows rapid characterization of interferences and avoids problems that arise in steady-state evaluations, such as orifice clogging and baseline drift. Unfortunately, more severe matrix effects are obtained with this technique than in steady-state experiments. In addition, by calculating analyte ratios across the flow injection profile, it is possible to diagnose interference effects as well as to determine the dilution factors necessary for alleviating the interference. However, at this time, this ratio technique is not completely effective, as it is limited by element-specific dispersion curves. Unlike conventional interference approaches that are often time-consuming, these methods offer efficient alternatives for evaluating and possibly avoiding matrix effects.

"Plasma-source Sector Mass Spectrometry With Array Detection"
J. Anal. At. Spectrom. 1999 Volume 14, Issue 8 Pages 1101-1110
David A. Solyom, Thomas W. Burgoyne and Gary M. Hieftje

Abstract: The combination of a mass spectrograph and an array detector possesses several potential advantages over more conventional methods of mass spectrometric analysis. The desirable features of this instrumental combination result from its most important quality, the ability to perform simultaneous analysis of an entire m/z range. These advantages include greater throughput (Felgett advantage), greater precision through isotope ratio determination, and superior analysis of fast, transient signals such as those produced by gas and liquid chromatographies, capillary electrophoresis, flow injection analysis, and laser ablation. Currently, two research groups are investigating the utility of incorporating ionization sources suitable for elemental analysis to mass spectrograph/array detector instrumentation. While progress has been made in both research groups, each project still has significant work ahead in order to realize fully the advantages of a sector mass spectrometer/array detector system. This review focuses primarily on the efforts of these two groups over approximately the last 6 years. However, basic discussions on several other topics including array detectors, the Mattauch-Herzog spectrograph geometry, and fundamental differences between simultaneous and scanning data acquisition are also presented.

"Online Gradient Calibration For Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1992 Volume 7, Issue 2 Pages 335-338
Timothy K. Starn and Gary M. Hieftje

Abstract: A microprocessor-controlled, automated, online method for generating calibration standards is described. Math. gradients, programmed with a high performance liquid chromatography pump module, mix stock and dilute solutions to form desired concentrations Online produced gradient calibrations are demonstrated to be comparable to those made with individual solution standards Advantages of the technique are the convenience and savings involved in maintaining a limited selection of stock solutions and the ease of performing standard additions calibrations. A possible drawback is a slight, but noticeable, time lag between successive gradient steps.
Spectrophotometry Computer Gradient technique Calibration

"Plasma-source Mass Spectrometry"
Int. J. Mass Spectrom. 1992 Volume 118, Issue 1 Pages 519-573
Gary M. Hieftje and Lori A. Norman

Abstract: A review is presented, with references that are grouped under the headings: general review articles (46), fundamental studies and instrument optimization (89), alternative sources and support gases (23), sample introduction systems (74), applications with chromatography and flow injection analysis (28), applications to environmental analysis (50), analyzes of biological and medical samples (45), applications in materials science (20), analysis of geological samples (117).
Mass spectrometry Review Optimization

"Radioluminescence Detector For The Flow Injection Determination Of Phosphorus As Vanadomolybdophosphoric Acid"
Anal. Chim. Acta 1999 Volume 402, Issue 1-2 Pages 267-274
Andrew M. Leach, Daniel L. Burden and Gary M. Hieftje

Abstract: A radioluminescent light source has been used in a detector for the how injection (FI) determination of phosphorus by means of the vanadomolybdophosphoric (VMP) acid spectrophotometric method. A comparison with previous studies in which lamp-based instrumentation was utilized proves that radioluminescence (RL) is a viable alternative source. RL enables the design of compact, inexpensive light sources for spectroscopic studies. Through the selection of a radioisotope and scintillation medium, the spectral and temporal characteristics of the source can be chosen independently. In this study, a broadband radioluminescent source provided detection limits similar to those of conventional lamp-based detectors while increasing the dynamic range of the method. Possible interferences caused by the use of a broadband light source have been explored as a function of the spectral region employed.

"New Spray Chamber For Use In Flow Injection Plasma Emission Spectrometry"
Anal. Chim. Acta 1994 Volume 286, Issue 2 Pages 155-167
Min Wu, Yoland Madrid, Jake A. Auxier and Gary M. Hieftje*

Abstract: A 200 W microwave plasma torch using Ar carrier and plasma support gases with a 2.45 GHz microwave generator, was used with a novel low-volume 4 cm vertical rotary spray chamber and a glass-concentric nebulizer in the cited technique (details given). The spray chamber was optimized for both continuous-flow (2 ml/min) nebulization, and discrete sample injection (200 µL). With an aqueous flow carrier, detection limits of 5-50 ng/ml were obtained for ten cations, with RSD typically 2.5% at sub ppm concentrations. Using methanol and ethanol as sample solvents, flowing at up to 2.5 ml/min, sensitivity decreases of approximately 40-50% were obtained compared to H2O.
Cations Environmental Spectrophotometry

"Evaluation Of Flow Injection Techniques For Microwave Plasma Torch Atomic-emission Spectrometry"
Anal. Chim. Acta 1993 Volume 277, Issue 1 Pages 1-8
Yolanda Madrid, Min Wu, Qinhan Jin and Gary M. Hieftje*

Abstract: Carrier solution, water, was pumped through an ultrasonic nebulizer to a microwave plasma torch (MPT; operating conditions tabulated). Sample containing Cu was pre-concentrated on a tapered micro-column (described) of C18-bonded silica and chelated with sodium diethyldithiocarbamate. After elution with ethanol the sample was drawn into a sample loop (75, 200, 250 or 500 µL); the carrier was directed through the sample loop, directing the sample into the MPT. The signal peak height obtained in flow injection (FI) mode (signal ~85% of that obtained with continuous nebulization) levelled off with a sample volume of 500 µL. The detection limit was 4.5 ng mL-1 with coefficient of variation of 1.8%; values were indistinguishable from results obtained with continuous sample injection. Copper in synthetic seawater was determined using the FI system. The pre-concentration. of the Cu prior to elution with ethanol eliminated errors due to Na+ and K+ present in a large number of natural matrices. The detection limit for Cu, following pre-concentration, was 0.16 ng mL-1 with coefficient of variation of ~3.2% at 500 ng mL-1 and recoveries of 94 to 97%.
Copper Sea Spectrophotometry C18 Preconcentration Interferences