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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R. Kenneth Marcus

Abbrev:
Marcus, R.K.
Other Names:
Address:
Department of Chemistry, Clemson University, Clemson, SC 29634-0973, USA
Phone:
864-656-5011
Fax:
864-656-6613

Citations 7

"Role Of Powering Geometries And Sheath Gas Composition On Operation Characteristics And The Optical Emission In The Liquid Sampling-atmospheric Pressure Glow Discharge"
Spectrochim. Acta B 2002 Volume 57, Issue 9 Pages 1473-1486
W. Clay Davis and R. Kenneth Marcus

Abstract: Characterization of the liquid sampling-atmospheric pressure glow discharge optical emission spectroscopy (LS-APGD-OES) source is described with regards to applications in low-flow separations such as capillary liquid chromatography and electrophoresis. Four powering modes are investigated, including the effects of the individual modes on current-voltage characteristics, analyte emission response, and temporal broadening of flow injection profiles. A concentric sheath gas is employed to stabilize the solution delivery at low liquid flow rates. Sheath gas composition (N2 or He) effects analyte emission responses as well as gas phase rotational and excitation temperatures. The respective powering modes both measures of temperature, with the OH rotational gas temperatures ranging from ~2100 to 3000 K and the Fe (I) excitation temperatures ranging from ~2400 to 3600 K. Rotational temperature values increase slightly when helium is employed as a sheath gas as opposed to nitrogen, with the corresponding excitation temperatures increasing somewhat as well. Analytical response curves for Na and Hg in the various powering modes demonstrate good linearity, with the limits of detection for the analytes found to be on the order of ~4-10 ppm for 5 µl injections; equating to absolute detection limits of between 20 and 45 ng. It is believed that the approach demonstrated here suggests further improvements that will permit applications in a wide variety of aqueous solution analyzes where low-flow rates and limited volumes are encountered.

"Optimization Of Hollow Cathode Diameter For Particle Beam/hollow Cathode Glow Discharge Atomic Emission Spectrometry"
Spectrochim. Acta B 2000 Volume 55, Issue 6 Pages 599-610
Melissa A. Dempster and R. Kenneth Marcus

Abstract: An evaluation of the effect of cathode diameter on analyte emission intensity for the particle beam/hollow cathode glow discharge atomic emission spectroscopy (PB-HC-AES) system is described. A high-efficiency thermoconcentric nebulizer is used to generate a fine aerosol of the aqueous solution flowing at rates of similar to 1 mL/min. Desolvation and use of a momentum separator/particle beam interface serves to introduce analyte particles into a heated HC glow discharge source for subsequent vaporization, atomization and excitation. The effects of discharge gas (He) pressure and current on emission responses for sodium and copper are evaluated in flow injection mode using 200 µL injection volumes for a series of fixed-length (25 mm) cylindrical HC having inner diameters of 2, 3, 5 and 7 mm. Analytical response curves obtained with the 2 mm i.d. HC for sodium and copper yield detection limits of 0.6 and 1.3 ppb in elemental Na and Cu, respectively, with less than 10% relative standard deviation (RSD) for triplicate injections over a concentration range of 0.5-20 ppm.
Interface

"Development Of A New Liquid Chromatography Method For The Separation And Speciation Of Organic And Inorganic Selenium Compounds Via Particle Beam-hollow Cathode Glow Discharge-optical Emission Spectroscopy"
J. Anal. At. Spectrom. 2002 Volume 17, Issue 2 Pages 99-103
W. Clay Davis, Fuxia Jin, Melissa A. Dempster, Jennifer L. Robichaud and R. Kenneth Marcus

Abstract: A system for the separation and detection of inorganic and organic selenium compounds utilizing particle beam-hollow cathode glow discharge-optical emission spectroscopy (PB-HC-OES) as a selenium-specific detector has been investigated. The PB interface includes a thermoconcentric nebulizer to generate a finely dispersed aerosol, a heated metal spray chamber for desolvation, and a two-stage momentum separator, which removes solvent vapor. The resulting beam of dry analyte particles are introduced into a heated (similar to250°C) hollow cathode, where they are vaporized, atomized and excited within the plasma. Using LC-PB-HC-OES the following compounds were examined: selenocystine, selenomethionine, selenoethionine, sodium selenate, and sodium selenite. A reverse phase ion-pairing chromatography method was developed to separate these five compounds (both organic and inorganic), with UV absorbance monitored at 210 nm. The Se I 204.0 nm atomic emission intensity was then monitored by coupling the LC column with the PB-HC-OES system. Emission responses for the selenium of both the organic and inorganic compounds in flow injection mode using 200 µL injection volumes indicate detection limits of similar to200 ppb (100 ng) with less than 10% RSD variability for triplicate injections over a range of 200-1960 ng. The retention times of the five analyte peaks are similar to those detected by UV absorbance, demonstrating the ability of the PB interface to preserve the chromatographic integrity of the separation. Optical emission detection of liquid chromatographic separations of the selenium-containing compounds demonstrates the feasibility of the PB-HC-OES system as a simple selenium-specific detector for liquid chromatography.
Nebulizer

"Analysis Of Amino Acids And Organometallic Compounds By Particle Beam-hollow Cathode Glow Discharge Atomic Emission Spectrometry"
J. Anal. At. Spectrom. 2000 Volume 15, Issue 1 Pages 43-48
Melissa A. Dempster and R. Kenneth Marcus

Abstract: An evaluation of the particle beam-hollow cathode glow discharge atomic emission spectroscopy (PB-HC-AES) system as an element-specific detector for liquid chromatography is described for aromatic amino acids and organomercury and organolead compounds. A high-efficiency thermoconcentric nebulizer is used to introduce analyte particles into a heated hollow cathode glow discharge source for subsequent vaporization, atomization and excitation. Emission responses for hydrogen and nitrogen of amino acids in flow injection mode using 200 µL injection volumes indicate detection limits of 0.13 and 3.6 ppm elemental H and N, respectively, with RSD < 10% for triplicate injections over a concentration range of 10^-3-10^-2 M. Analysis of the response of hydrogen and nitrogen emission signal intensities to differences in amino acid stoichiometries indicates the potential of the PB-HC-AES system for the determination of empirical formulas based on H I/N I intensity ratios. Detection limits for metals and non-metals in organomercury compounds as determined through flow injection of 200 µL sample volumes fall in the sub ppm range. Liquid chromatographic separations of both amino acids and organolead compounds demonstrate the feasibility of the PB-HC-AES system as a detector for liquid chromatography. Retention times for 20 µL injections of the selected component mixtures as determined by C I emission for amino acids and Pb I emission for organolead compounds correlate well with the corresponding UV absorbance results.
Preconcentration Derivatization Speciation

"Nebulization And Analysis Characteristics Of A Particle-beam Hollow-cathode Glow-discharge Atomic-emission Spectrometry System"
J. Anal. At. Spectrom. 1996 Volume 11, Issue 7 Pages 483-490
Jianzhang You, Patrick A. Depalma Jr. and R. Kenneth Marcus

Abstract: A detailed evaluation of the nebulization characteristics of a particle beam/hollow cathode glow discharge atomic emission spectrometry system is described, The optimization of sample introduction and particle beam interface operation was further evaluated for applications in elemental analysis for a number of transition metals, A high efficiency thermoconcentric nebulizer, coupled to a particle beam LC-MS interface, was employed to introduce analyte particles into a heated hollow cathode glow discharge source in either flow injection or continuous-flow mode, The measurement of pressure and temperature in the desolvation chamber, along with the addition of a helium supplement gas, provides an insight into the sample/particle transport mechanism, The effects of capillary size (inner diameter) and solvent composition (methanol-water volume ratio) at various liquid Bow rates were studied to evaluate optimum sample introduction conditions, Calibration graphs of Cu, Pb, Fe and Mg in the range 50 ppb-10 ppm show promising linearity under optimized conditions, The variability of multiple injections at a single concentration is less than 15% RSD over this concentration range, The limits of detection for Cu, Pb, Fe and Mg are 12, 25, 20 and 15 ppb, respectively, for 200 µl injection volumes.
Copper Iron Tin Magnesium Spectrophotometry Mass spectrometry LC Optimization

"Total Protein Determinations By Particle Beam/Hollow Cathode Optical Emission Spectroscopy"
Anal. Chem. 2003 Volume 75, Issue 18 Pages 4801-4810
Fuxia Jin, Keith Lenghaus, James Hickman and R. Kenneth Marcus

Abstract: A novel method for quantitative total protein determinations is presented. Total protein content is determined by particle beam/hollow cathode optical emission spectroscopy (PB/HC-OES) through monitoring of carbon atomic emission. The PB/HC-OES offers such advantages as ease of operation, exclusion of labor-intensive sample pretreatment processes, rapid analysis, high sensitivity, and low detection limit. The method could also be adapted to be integrated to current microfluidics devices. Parametric optimization for sample introduction, nebulization, desolvation, and hollow cathode source conditions is performed for the analysis of aqueous bovine serum albumin solutions. Response curves of C (I) 193.0-nm emission were obtained under the optimized conditions with both 10% HCl and 100 µg/mL KCl added to the sample matrix as potential carriers. The detection limit for triplicate injections of bovine serum albumin standards was found to be on the single-nanogram level with 200 µL injections. The addition of KCl significantly improved the sensitivity, supporting the proposed 'carrier effect' of chloride salts in the particle transport process. Results obtained here suggest a range of applications for the use of the PB/HC-OES source for total protein determinations; emphasis here is future use in assessing protein quantification in microfluidic systems.

"Total Protein Determinations By Particle Beam/hollow Cathode Optical Emission Spectroscopy (PB/HC-OES) System III: Investigation Of Carrier Salts For Enhanced Particle Transport"
Anal. Bioanal. Chem. 2004 Volume 380, Issue 2 Pages 204-211
Fuxia Jin, James J. Hickman, Keith Lenghaus and R. Kenneth Marcus

Abstract: Particle beam hollow cathode optical emission spectroscopy (PB/HC-OES) is evaluated as a generic tool for total protein determinations by monitoring the carbon atomic emission (C (I) 193.0 nm) resultant from dissociated analyte species. Previous studies demonstrated the capability of the PB/HC-OES system for total protein determinations with limits of detection for bovine serum albumin (BSA) samples being at the single-nanogram level for 200 µL injections. Non-linear behavior across the concentration range in the calibration curve was observed due to the poor transport of small particles (owing to low analyte concentrations) through the PB interface. The potential use of non-volatile salts as carrier agents is investigated in the determination of protein samples by PB/HC-OES. A range of chloride salts (different cations), potassium salts (different anions), and an organic modifier (ammonium acetate) is investigated here for possible use as carriers upon addition as sample injection matrices for protein samples. The analyte response curves of BSA samples with KCl added as the sample injection matrix show higher sensitivity, better linearity (R2) and subsequently lower detection limits in comparison to those obtained with water, HCl, KNO3 or ammonium acetate as carrier matrices.