Akbar Montaser - Profile on Academia.edu (original) (raw)

Papers by Akbar Montaser

Research paper thumbnail of Forensic Analysis of Acrylic Copolymer Fibers by Infrared Microscopy

Applied Spectroscopy, 1993

Ratios of absorbance peak areas (Ac_o/~Z~C~N) of carbonyi and nitrile groups were obtained for si... more Ratios of absorbance peak areas (Ac_o/~Z~C~N) of carbonyi and nitrile groups were obtained for single acrylic fibers by IR microscopy. The precision of the comonomer ratios was evaluated for potential application in forensic fiber examinations. Precise (RSDs less than 0.4%) results for repetitive analyses of one location on a fiber were obtained. Precision was reduced when the cited ratio was measured at adjacent locations along the length of a single fiber. A further deterioration in precision was observed when different fiber specimens of the same type were analyzed. Analysis of different acrylic fiber specimens of the same type yielded RSDs which ranged from 2 to 6%. Fibers with diameters which ranged from 13 to 43 pm were examined. Precision was decreased for fibers with smaller diameters. Preliminary results indicate that acrylic fibers can differ by manufacturer as indicated by Ac_o/Ac~N.

Research paper thumbnail of Computer simulation of argon-nitrogen and argon-oxygen inductively coupled plasmas

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by co... more The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by computer simulation. The resuits from the simulations are compared with existing experimental data. The reasons for the deviations are discussed, and inferences are drawn to connect the simulated results to recommendations for practical analytical measurements using ICP atomic emission and ICP mass spectrometries. The effect of the concentration of N2 and 02 in the outer gas flow (0%-100%) and injector gas flow (0%-20%) and the influence of the active power (800-1500 W) on the distribution of the plasma temperatures, electric and magnetic fields and tangential velocity are investigated. In general, mixed-gas plasmas move closer to the state of local thermodynamic equilibrium (LTE) as the concentrations of the molecular gases (N2 and 02) in the outer gas flow are increased. In contrast with the experimental results, the LTE model predicts that mixed-gas plasmas have maximum temperatures (9900-10100 K) comparable with Ar ICPs (10 600 K). The predicted temperature of the mixed-gas plasma is reduced as the concentration of the molecular gas is increased. The temperatures of Ar-O2 ICPs are estimated to be higher than those of Ar-N2 plasmas, except when the outer gas flow contains 100% N2 or 02. © 1997 Elsevier Science B.V.

Research paper thumbnail of A Direct Injection High-Efficiency Nebulizer for Inductively Coupled Plasma Mass Spectrometry

A Direct Injection High-Efficiency Nebulizer for Inductively Coupled Plasma Mass Spectrometry

Analytical Chemistry, 1998

A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced fo... more A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced for argon inductively coupled plasma (Ar ICP) spectrometry. The DIHEN may be operated at solution uptake rates of 1-100 microL/min. Analytical performance indexes for the DIHEN and fundamental characteristics of the aerosol produced are obtained using an ICP mass spectrometer (ICPMS) and a two-dimensional phase Doppler particle analyzer (2D PDPA), respectively. Results are compared to those obtained with a conventional crossflow pneumatic nebulizer (PN), equipped with a Scott-type spray chamber. Droplet sizes and velocities produced with the DIHEN are smaller than those reported for the direct injection nebulizer (DIN). The DIHEN offers optimal sensitivity at low injector gas flow rates (approximately 0.25 L/min) and high rf power (approximately 1.5 kW). For the 17 elements tested, detection limits (ppt) and sensitivities achieved with the DIHEN (at 85 microL/min) are similar to, or better than, those obtained on the same instrument using the PN (at 1 mL/min). However, because the primary aerosol is injected directly into the plasma, oxide-to-metal ion ratios (MO+/M+) are high, as in the case of the DIN. The utility of the DIHEN for the analysis of small-volume samples is demonstrated by microscale flow injection analysis (muFIA) of Cr bound to human lung DNA. Detection of Cr at the femtogram level is feasible.

Research paper thumbnail of Reduction of molecular ion interferences with hexapole collision cell in direct injection nebulization–inductively coupled plasma mass spectrometry

Reduction of molecular ion interferences with hexapole collision cell in direct injection nebulization–inductively coupled plasma mass spectrometry

Journal of Analytical Atomic Spectrometry, 2003

... The authors are grateful to C. Pickhardt (Central Department of Analytical Chemistry, Researc... more ... The authors are grateful to C. Pickhardt (Central Department of Analytical Chemistry, Research Centre Juelich) and John A. McLean (GWU) for constructive discussions and assistance. ... 7, JAMcLean, JS Becker, SF Boulyga, H.-J. Dietze and A. Montaser, Int. ...

Research paper thumbnail of Inductively Coupled Plasmas in Analytical Atomic Spectrotnetry

Research paper thumbnail of Two-temperature model for the simulation of atmospheric-pressure helium ICPs

Applied Spectroscopy, 1995

A two-temperature model (2-T model) was used to predict fundamental properties of pure helium ind... more A two-temperature model (2-T model) was used to predict fundamental properties of pure helium inductively coupled plasmas (He ICPs). Plasma characteristics with the use of the 2-T model were compared to those obtained by the local thermodynamic equilibrum (LTE) model for the He ICP, to those of an Ar ICP, and to the existing experimental data. The distributions of electron and heavy-particle temperatures, electron number density, and electric and magnetic fields were obtained as a function of the internal diameters of the torch, the gas flow rates, the gap between the plasma tube and the MACOR insert, the generator frequency, and the active power. Overall, the He ICP was predicted to have a much higher electron temperature (>12,000 K) in the load coil region, but its axial heavy-particle and electron temperatures (~2000 K) at the analytical zone were lower than those of the Ar ICP (4000-6000 K). The high-temperature region in the He ICP was constricted to a smaller region close to the wall of the plasma confinement tube as compared to that in the Ar ICP. Most of the input power in the He ICP was lost through the plasma quartz tube. The magnetic and electric fields inside the induction coil in the helium plasma were approximately one order of magnitude higher than those in the argon plasma.

Research paper thumbnail of In Situ Visualization and Characterization of Aerosol Droplets in an Inductively Coupled Plasma

Analytical Chemistry, 2005

Laser-scattering techniques are utilized for the first time to visualize the aerosol droplets in ... more Laser-scattering techniques are utilized for the first time to visualize the aerosol droplets in an inductively coupled plasma (ICP) torch from the nebulizer tip to the site of analytical measurements. The resulting images provide key information about the spatial distribution of the aerosol introduced by direct injection and conventional sample introduction devices: (1) a direct injection highefficiency nebulizer (DIHEN); (2) a large-bore DIHEN; and (3) a MicroFlow PFA nebulizer with a PFA Scott-type spray chamber. Moreover, particle image velocimetry is used to study the in situ behavior of the aerosol before interaction with the plasma, while the individual surviving droplets are explored by particle tracking velocimetry. Directly introduced aerosols are highly scattered across the plasma torch as a result of their radial motion, indicating less than optimum sample consumption efficiency for the current direct injection devices. Further, the velocity distribution of the surviving droplets demonstrates the importance of the initial droplet velocities in complete desolvation of the aerosol for optimum analytical performance in ICP spectrometries. These new observations are critical in the design of the next-generation direct injection devices for lower sample consumption, higher sensitivity, lower noise levels, suppressed matrix effects, and developing smart spectrometers.

Research paper thumbnail of Determination of 236U/238U isotope ratio in contaminated environmental samples using different ICP-MS instruments

Determination of 236U/238U isotope ratio in contaminated environmental samples using different ICP-MS instruments

Journal of Analytical Atomic Spectrometry, 2002

... Sergei F. Boulyga, Janna L. Matusevich, Vladislav P. Mironov, Vladimir P. Kudrjashov, Ludwik ... more ... Sergei F. Boulyga, Janna L. Matusevich, Vladislav P. Mironov, Vladimir P. Kudrjashov, Ludwik Halicz, Irina Segal, John A. McLean, Akbar Montaser and J. Sabine Becker J. Anal. At. Spectrom., 2002, 17, 958-964. DOI: 10.1039/B201803A , Paper. ...

Research paper thumbnail of Determination of Depleted Uranium in Urine via Isotope Ratio Measurements Using Large-Bore Direct Injection High Efficiency Nebulizer–Inductively Coupled Plasma Mass Spectrometry

Determination of Depleted Uranium in Urine via Isotope Ratio Measurements Using Large-Bore Direct Injection High Efficiency Nebulizer–Inductively Coupled Plasma Mass Spectrometry

Applied Spectroscopy, 2004

Inductively coupled plasma mass spectrometry (ICP-MS), coupled with a large-bore direct injection... more Inductively coupled plasma mass spectrometry (ICP-MS), coupled with a large-bore direct injection high efficiency nebulizer (LB-DIHEN), was utilized to determine the concentration and isotopic ratio of uranium in 11 samples of synthetic urine spiked with varying concentrations and ratios of uranium isotopes. Total U concentrations and (235)U/(238)U isotopic ratios ranged from 0.1 to 10 microg/L and 0.0011 and 0.00725, respectively. The results are compared with data from other laboratories that used either alpha-spectrometry or quadrupole-based ICP-MS with a conventional nebulizer-spray chamber arrangement. Severe matrix effects due to the high total dissolved solid content of the samples resulted in a 60 to 80% loss of signal intensity, but were compensated for by using (233)U as an internal standard. Accurate results were obtained with LB-DIHEN-ICP-MS, allowing for the positive identification of depleted uranium based on the (235)U/(238)U ratio. Precision for the (235)U/(238)U ratio is typically better than 5% and 15% for ICP-MS and alpha-spectrometry, respectively, determined over the concentrations and ratios investigated in this study, with the LB-DIHEN-ICP-MS system providing the most accurate results. Short-term precision (6 min) for the individual (235)U and (238)U isotopes in synthetic urine is better than 2% (N = 7), compared to approximately 5% for conventional nebulizer-spray chamber arrangements and >10% for alpha-spectrometry. The significance of these measurements is discussed for uranium exposure assessment of Persian Gulf War veterans affected by depleted uranium ammunitions.

Research paper thumbnail of Atmospheric-pressure helium inductively coupled plasmas for elemental mass spectrometry

Atmospheric-pressure helium inductively coupled plasmas for elemental mass spectrometry

Applied Spectroscopy, 1996

Analytical and fundamental characteristics of helium inductively coupled plasma mass spectrometry... more Analytical and fundamental characteristics of helium inductively coupled plasma mass spectrometry (He ICPMS) were explored for atmospheric-pressure plasmas generated in a 13-mm He ICP torch with the use of a prototype ICPMS equipped with an analogue ...

Research paper thumbnail of Nebulizer diagnostics: fundamental parameters, challenges, and techniques on the horizon

Nebulizer diagnostics: fundamental parameters, challenges, and techniques on the horizon

Journal of Analytical Atomic Spectrometry, 1998

... 1. Would not change key fundamental properties of the plasma: Plasma gas temperature ... or p... more ... 1. Would not change key fundamental properties of the plasma: Plasma gas temperature ... or particles in a polydispersion to acquire an accurate estimate (±5%) of the aerosol parameters listed in Table ... 5 High-speed photographs showing variations in aerosol break-up patterns. ...

Research paper thumbnail of Simulation of droplet heating and desolvation in an inductively coupled plasma — Part I

Spectrochimica Acta Part B-atomic Spectroscopy, 2001

A numerical model is developed to consider for the first time droplet coalescence along with tran... more A numerical model is developed to consider for the first time droplet coalescence along with transport, heating and desolvation in an argon inductively coupled plasma (Ar ICP). The direct simulation Monte Carlo (DSMC) method and the Ashgriz-Poo model are used, respectively, to compute droplet-droplet interactions and to determine the outcome of droplet collisions. Molecular dynamics (MD) simulations support the use of the Ashgriz-Poo coalescence model for small droplet coalescence. Simulations predict spatial maps of droplet number and mass densities within an Ar ICP for a conventional nebulizer-spray chamber arrangement, a direct injection high efficiency nebulizer (DIHEN), and a large bore DIHEN (LB-DIHEN). The primary findings are: (1) even at 1500 W, the collisions of the droplets in the plasma lead primarily to coalescence, particularly for direct aerosol injection; (2) the importance of coalescence in a spray simulation exhibits a complex relationship with the gas temperature and droplet size; (3) DIHEN droplets penetrate further into the Ar ICP when coalescence is considered; and (4) droplets from a spray chamber or the LB-DIHEN coalesce less frequently than those from a DIHEN. The implications of these predictions in spectrochemical analysis in ICP spectrometry are discussed. ᮊ

Research paper thumbnail of Internalization of Carcinogenic Lead Chromate Particles by Cultured Normal Human Lung Epithelial Cells: Formation of Intracellular Lead-Inclusion Bodies and Induction of Apoptosis

Internalization of Carcinogenic Lead Chromate Particles by Cultured Normal Human Lung Epithelial Cells: Formation of Intracellular Lead-Inclusion Bodies and Induction of Apoptosis

Toxicology and Applied Pharmacology, 1999

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead... more Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

Research paper thumbnail of A Large Bore-Direct Injection High Efficiency Nebulizer for Inductively Coupled Plasma Spectrometry

A Large Bore-Direct Injection High Efficiency Nebulizer for Inductively Coupled Plasma Spectrometry

Analytical Chemistry, 2000

A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less pro... more A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less prone to capillary blockage and optimally operates at low nebulizer gas pressures compared with the conventional DIHEN used for inductively coupled plasma (ICP) spectrometries. The aerosol quality is examined using a two-dimensional phase Doppler particle analyzer (2D PDPA), and analytical figures of merits are acquired by ICP mass spectrometry. Compared with the DIHEN, the LB-DIHEN produces larger droplets, but the velocity distributions and mean droplet velocities are narrower and lower, respectively, providing longer residence times for the droplets in the plasma. High RF power (1500 W), low nebulizer gas flow rates (0.25-0.35 L/min), and low solution uptake rates (80-110 microL/min) are required to operate the LB-DIHEN at optimum conditions for ICPMS. Detection limits and sensitivities measured with the LB-DIHEN are superior to those of a conventional nebulizer-spray chamber combination, but precision is inferior. The performance of the LB-DIHEN is further explored in the determination of trace elements in an herbal extract.

Research paper thumbnail of Demountable direct injection high efficiency nebulizer for inductively coupled plasma mass spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2004

A low cost, demountable direct injection high efficiency nebulizer (d-DIHEN) is introduced that p... more A low cost, demountable direct injection high efficiency nebulizer (d-DIHEN) is introduced that provides an adjustable solution capillary, allowing fundamental studies to improve operational characteristics of the micronebulizers, aerosol properties, and analytical figures of merit in inductively coupled plasma (ICP) spectrometries. Similar to the DIHEN and the large bore-DIHEN (LB-DIHEN), the d-DIHEN requires high RF power (1500 W), low nebulizer gas flow rates (approx. 0.16 lymin), and low solution uptake rates (1-100 mlymin) for optimal measurements in ICP mass spectrometry (ICPMS). In contrast to the DIHEN and LB-DIHEN, the optimum position for the d-DIHEN nozzle is located 5 mm (rather than 2 mm) below the end of the torch intermediate tube, thus reducing chances of accidental nebulizer tip meltdown. Compared with the DIHEN, the d-DIHEN produces smaller droplets with narrower droplet distributions and lower mean droplet velocities, characteristics important for improved sample-plasma interaction. Sensitivity, detection limits, and precision are superior with the d-DIHEN compared to conventional nebulizer-spray chamber arrangements and other direct injection nebulizers, especially at low solution uptake rates (-40 mly min). In general, oxide ratios for the d-DIHEN and DIHEN are low and similar at solution uptake rates of 10 mlymin or less. Above 10 mlymin, the d-DIHEN provides lower oxide ratios than the DIHEN. For example, the oxide ratio for Ce increases from 0.6% to 3.8% (d-DIHEN) and 0.5 to 7.6% (DIHEN) as the solution uptake rate is increased from 5 to 85 mlymin. Doubly charged ratios for Ba are also lower for the d-DIHEN at all solution uptake rates compared to the DIHEN. The utility of the d-DIHEN is investigated in the analysis of a reference material (Lyphochek urine metals control) at low (Level 1) and high (Level 2) concentration levels. ᮊ

Research paper thumbnail of Formation and fundamental characteristics of novel free-running helium inductively coupled plasmas

Journal of Analytical Atomic Spectrometry, 2000

This report is the ®rst study on the formation, stabilization and fundamental investigation of fr... more This report is the ®rst study on the formation, stabilization and fundamental investigation of free-running helium inductively coupled plasmas (He ICPs). The plasma was operated at 600±900 W with a total helium gas ow of less than 10 L min 21 . The shape and the physical appearance of free-running helium plasmas differ markedly from the He ICP sources reported previously using a crystal-controlled generator. Although the freerunning helium plasma appears annular, high-speed video studies reveal that the plasma rotates at a frequency of 75±275 Hz. Lateral pro®les of emission spectra of the free-running discharge viewed end-on provide rotational temperature (T rot ), excitation temperature (T exc ), and electron number density (n e ) of 1600±1800 K, 3800±4300 K, and 3.0 to 12610 13 cm 23 , respectively. These fundamental characteristics are compared to those reported previously for crystal-controlled He ICPs and Ar ICPs.

Research paper thumbnail of Direct injection high efficiency nebulizer-inductively coupled plasma mass spectrometry for analysis of petroleum samples

Spectrochimica Acta Part B-atomic Spectroscopy, 2003

Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (... more Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (ICPMS) is investigated for analysis of petroleum samples dissolved in volatile organic solvents. To minimize solvent loading, the solution uptake rate is reduced to 10 mlymin, far less than the level (85 mlymin) commonly used for aqueous sample introduction with the DIHEN, and oxygen is added to the nebulizer gas flow and outer flow of the ICP. Factorial design is applied to investigate the effect of nebulizer tip position within the torch and the nebulizer and intermediate gas flow rates on the precision and the net signal intensity of the elements tested for multielemental analysis. Cluster analysis and principal component analysis are performed to distinguish the behavior of different isotopes, oxide species and doubly charged ions. The best operating conditions at a solution uptake rate of 10 mly min are: RF powers1500 W, nebulizer gas flow rates0.10-0.12 lymin, intermediate gas flow rates1.5 lymin and DIHEN tip positions3-4 mm below the top of the torch intermediate tube. Acceptable recoveries (100"10%) and good precision (less than 3% relative standard deviation) are obtained for trace elemental analysis in organic matrices (a certified gas oil sample and a custom-made certified reference material) using flow injection analysis. Because of high blank levels, detection limits are 1-3 orders of magnitude higher for organic sample introduction than those acquired for aqueous solutions. ᮊ

Research paper thumbnail of Direct injection high efficiency nebulization in inductively coupled plasma mass spectrometry under cool and normal plasma conditions

Applied Spectroscopy, 2000

The direct injection high ef ciency nebulizer (DIHEN) was investigated for application to inducti... more The direct injection high ef ciency nebulizer (DIHEN) was investigated for application to inductively coupled plasma m ass spectrom etry (ICPMS) with a cool plasma. Elem ents are organized into three categories based on their perform ance in the cool and normal plasma. Sensitivity, precision, and detection limits are presen ted for elem ents ( 39 K, 40 Ca, and 56 Fe) that suffer from m ass spectra l interferences ( 38 ArH 1 , 40 Ar 1 , and 40 Ar 16 O 1 ) derived from the plasma gas. Figures of merit are also reported for a group of elements that are suitable for analysis using either the cool or norm al plasma condition. In a departure from previous published accounts, however, a group of elements is investigated that is suitable for analysis in the cool plasma only by m easurem ent of the metal oxide ion because the sensitivity and precision of the atomic ion are inferior to those obtained for the m etal oxide ion. The sensitivity and precision obtained for these m olecular species are comparable to those obtained for the atomic ions of elem ents that are suitable for analysis using the cool plasma. Calibration curves for the m etal oxide signal as a function of the m etal concentration in the cool plasma are linear over six orders of m agnitude, covering the concentration range from 1 ppt to 1 ppm. Nerve tonic tablets that contain Na, Mg, K , Ca, and Fe in unspeci ed amounts were analyzed under cool plasma conditions. Index Headings: Cool plasm a; Inductively coupled plasma; Inductively coupled plasma mass spectrometry; Direct injection high efciency nebulizer.

Research paper thumbnail of Simulation of droplet heating and desolvation in inductively coupled plasma—part II: coalescence in the plasma

Spectrochimica Acta Part B-atomic Spectroscopy, 2003

A numerical model is developed to consider for the first time droplet coalescence along with tran... more A numerical model is developed to consider for the first time droplet coalescence along with transport, heating and desolvation in an argon inductively coupled plasma (Ar ICP). The direct simulation Monte Carlo (DSMC) method and the Ashgriz-Poo model are used, respectively, to compute droplet-droplet interactions and to determine the outcome of droplet collisions. Molecular dynamics (MD) simulations support the use of the Ashgriz-Poo coalescence model for small droplet coalescence. Simulations predict spatial maps of droplet number and mass densities within an Ar ICP for a conventional nebulizer-spray chamber arrangement, a direct injection high efficiency nebulizer (DIHEN), and a large bore DIHEN (LB-DIHEN). The primary findings are: (1) even at 1500 W, the collisions of the droplets in the plasma lead primarily to coalescence, particularly for direct aerosol injection; (2) the importance of coalescence in a spray simulation exhibits a complex relationship with the gas temperature and droplet size; (3) DIHEN droplets penetrate further into the Ar ICP when coalescence is considered; and (4) droplets from a spray chamber or the LB-DIHEN coalesce less frequently than those from a DIHEN. The implications of these predictions in spectrochemical analysis in ICP spectrometry are discussed. ᮊ

Research paper thumbnail of Computer simulation of argon-nitrogen and argon-oxygen inductively coupled plasmas

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by co... more The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by computer simulation. The resuits from the simulations are compared with existing experimental data. The reasons for the deviations are discussed, and inferences are drawn to connect the simulated results to recommendations for practical analytical measurements using ICP atomic emission and ICP mass spectrometries. The effect of the concentration of N2 and 02 in the outer gas flow (0%-100%) and injector gas flow (0%-20%) and the influence of the active power (800-1500 W) on the distribution of the plasma temperatures, electric and magnetic fields and tangential velocity are investigated. In general, mixed-gas plasmas move closer to the state of local thermodynamic equilibrium (LTE) as the concentrations of the molecular gases (N2 and 02) in the outer gas flow are increased. In contrast with the experimental results, the LTE model predicts that mixed-gas plasmas have maximum temperatures (9900-10100 K) comparable with Ar ICPs (10 600 K). The predicted temperature of the mixed-gas plasma is reduced as the concentration of the molecular gas is increased. The temperatures of Ar-O2 ICPs are estimated to be higher than those of Ar-N2 plasmas, except when the outer gas flow contains 100% N2 or 02. © 1997 Elsevier Science B.V.

Research paper thumbnail of Forensic Analysis of Acrylic Copolymer Fibers by Infrared Microscopy

Applied Spectroscopy, 1993

Ratios of absorbance peak areas (Ac_o/~Z~C~N) of carbonyi and nitrile groups were obtained for si... more Ratios of absorbance peak areas (Ac_o/~Z~C~N) of carbonyi and nitrile groups were obtained for single acrylic fibers by IR microscopy. The precision of the comonomer ratios was evaluated for potential application in forensic fiber examinations. Precise (RSDs less than 0.4%) results for repetitive analyses of one location on a fiber were obtained. Precision was reduced when the cited ratio was measured at adjacent locations along the length of a single fiber. A further deterioration in precision was observed when different fiber specimens of the same type were analyzed. Analysis of different acrylic fiber specimens of the same type yielded RSDs which ranged from 2 to 6%. Fibers with diameters which ranged from 13 to 43 pm were examined. Precision was decreased for fibers with smaller diameters. Preliminary results indicate that acrylic fibers can differ by manufacturer as indicated by Ac_o/Ac~N.

Research paper thumbnail of Computer simulation of argon-nitrogen and argon-oxygen inductively coupled plasmas

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by co... more The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by computer simulation. The resuits from the simulations are compared with existing experimental data. The reasons for the deviations are discussed, and inferences are drawn to connect the simulated results to recommendations for practical analytical measurements using ICP atomic emission and ICP mass spectrometries. The effect of the concentration of N2 and 02 in the outer gas flow (0%-100%) and injector gas flow (0%-20%) and the influence of the active power (800-1500 W) on the distribution of the plasma temperatures, electric and magnetic fields and tangential velocity are investigated. In general, mixed-gas plasmas move closer to the state of local thermodynamic equilibrium (LTE) as the concentrations of the molecular gases (N2 and 02) in the outer gas flow are increased. In contrast with the experimental results, the LTE model predicts that mixed-gas plasmas have maximum temperatures (9900-10100 K) comparable with Ar ICPs (10 600 K). The predicted temperature of the mixed-gas plasma is reduced as the concentration of the molecular gas is increased. The temperatures of Ar-O2 ICPs are estimated to be higher than those of Ar-N2 plasmas, except when the outer gas flow contains 100% N2 or 02. © 1997 Elsevier Science B.V.

Research paper thumbnail of A Direct Injection High-Efficiency Nebulizer for Inductively Coupled Plasma Mass Spectrometry

A Direct Injection High-Efficiency Nebulizer for Inductively Coupled Plasma Mass Spectrometry

Analytical Chemistry, 1998

A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced fo... more A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced for argon inductively coupled plasma (Ar ICP) spectrometry. The DIHEN may be operated at solution uptake rates of 1-100 microL/min. Analytical performance indexes for the DIHEN and fundamental characteristics of the aerosol produced are obtained using an ICP mass spectrometer (ICPMS) and a two-dimensional phase Doppler particle analyzer (2D PDPA), respectively. Results are compared to those obtained with a conventional crossflow pneumatic nebulizer (PN), equipped with a Scott-type spray chamber. Droplet sizes and velocities produced with the DIHEN are smaller than those reported for the direct injection nebulizer (DIN). The DIHEN offers optimal sensitivity at low injector gas flow rates (approximately 0.25 L/min) and high rf power (approximately 1.5 kW). For the 17 elements tested, detection limits (ppt) and sensitivities achieved with the DIHEN (at 85 microL/min) are similar to, or better than, those obtained on the same instrument using the PN (at 1 mL/min). However, because the primary aerosol is injected directly into the plasma, oxide-to-metal ion ratios (MO+/M+) are high, as in the case of the DIN. The utility of the DIHEN for the analysis of small-volume samples is demonstrated by microscale flow injection analysis (muFIA) of Cr bound to human lung DNA. Detection of Cr at the femtogram level is feasible.

Research paper thumbnail of Reduction of molecular ion interferences with hexapole collision cell in direct injection nebulization–inductively coupled plasma mass spectrometry

Reduction of molecular ion interferences with hexapole collision cell in direct injection nebulization–inductively coupled plasma mass spectrometry

Journal of Analytical Atomic Spectrometry, 2003

... The authors are grateful to C. Pickhardt (Central Department of Analytical Chemistry, Researc... more ... The authors are grateful to C. Pickhardt (Central Department of Analytical Chemistry, Research Centre Juelich) and John A. McLean (GWU) for constructive discussions and assistance. ... 7, JAMcLean, JS Becker, SF Boulyga, H.-J. Dietze and A. Montaser, Int. ...

Research paper thumbnail of Inductively Coupled Plasmas in Analytical Atomic Spectrotnetry

Research paper thumbnail of Two-temperature model for the simulation of atmospheric-pressure helium ICPs

Applied Spectroscopy, 1995

A two-temperature model (2-T model) was used to predict fundamental properties of pure helium ind... more A two-temperature model (2-T model) was used to predict fundamental properties of pure helium inductively coupled plasmas (He ICPs). Plasma characteristics with the use of the 2-T model were compared to those obtained by the local thermodynamic equilibrum (LTE) model for the He ICP, to those of an Ar ICP, and to the existing experimental data. The distributions of electron and heavy-particle temperatures, electron number density, and electric and magnetic fields were obtained as a function of the internal diameters of the torch, the gas flow rates, the gap between the plasma tube and the MACOR insert, the generator frequency, and the active power. Overall, the He ICP was predicted to have a much higher electron temperature (>12,000 K) in the load coil region, but its axial heavy-particle and electron temperatures (~2000 K) at the analytical zone were lower than those of the Ar ICP (4000-6000 K). The high-temperature region in the He ICP was constricted to a smaller region close to the wall of the plasma confinement tube as compared to that in the Ar ICP. Most of the input power in the He ICP was lost through the plasma quartz tube. The magnetic and electric fields inside the induction coil in the helium plasma were approximately one order of magnitude higher than those in the argon plasma.

Research paper thumbnail of In Situ Visualization and Characterization of Aerosol Droplets in an Inductively Coupled Plasma

Analytical Chemistry, 2005

Laser-scattering techniques are utilized for the first time to visualize the aerosol droplets in ... more Laser-scattering techniques are utilized for the first time to visualize the aerosol droplets in an inductively coupled plasma (ICP) torch from the nebulizer tip to the site of analytical measurements. The resulting images provide key information about the spatial distribution of the aerosol introduced by direct injection and conventional sample introduction devices: (1) a direct injection highefficiency nebulizer (DIHEN); (2) a large-bore DIHEN; and (3) a MicroFlow PFA nebulizer with a PFA Scott-type spray chamber. Moreover, particle image velocimetry is used to study the in situ behavior of the aerosol before interaction with the plasma, while the individual surviving droplets are explored by particle tracking velocimetry. Directly introduced aerosols are highly scattered across the plasma torch as a result of their radial motion, indicating less than optimum sample consumption efficiency for the current direct injection devices. Further, the velocity distribution of the surviving droplets demonstrates the importance of the initial droplet velocities in complete desolvation of the aerosol for optimum analytical performance in ICP spectrometries. These new observations are critical in the design of the next-generation direct injection devices for lower sample consumption, higher sensitivity, lower noise levels, suppressed matrix effects, and developing smart spectrometers.

Research paper thumbnail of Determination of 236U/238U isotope ratio in contaminated environmental samples using different ICP-MS instruments

Determination of 236U/238U isotope ratio in contaminated environmental samples using different ICP-MS instruments

Journal of Analytical Atomic Spectrometry, 2002

... Sergei F. Boulyga, Janna L. Matusevich, Vladislav P. Mironov, Vladimir P. Kudrjashov, Ludwik ... more ... Sergei F. Boulyga, Janna L. Matusevich, Vladislav P. Mironov, Vladimir P. Kudrjashov, Ludwik Halicz, Irina Segal, John A. McLean, Akbar Montaser and J. Sabine Becker J. Anal. At. Spectrom., 2002, 17, 958-964. DOI: 10.1039/B201803A , Paper. ...

Research paper thumbnail of Determination of Depleted Uranium in Urine via Isotope Ratio Measurements Using Large-Bore Direct Injection High Efficiency Nebulizer–Inductively Coupled Plasma Mass Spectrometry

Determination of Depleted Uranium in Urine via Isotope Ratio Measurements Using Large-Bore Direct Injection High Efficiency Nebulizer–Inductively Coupled Plasma Mass Spectrometry

Applied Spectroscopy, 2004

Inductively coupled plasma mass spectrometry (ICP-MS), coupled with a large-bore direct injection... more Inductively coupled plasma mass spectrometry (ICP-MS), coupled with a large-bore direct injection high efficiency nebulizer (LB-DIHEN), was utilized to determine the concentration and isotopic ratio of uranium in 11 samples of synthetic urine spiked with varying concentrations and ratios of uranium isotopes. Total U concentrations and (235)U/(238)U isotopic ratios ranged from 0.1 to 10 microg/L and 0.0011 and 0.00725, respectively. The results are compared with data from other laboratories that used either alpha-spectrometry or quadrupole-based ICP-MS with a conventional nebulizer-spray chamber arrangement. Severe matrix effects due to the high total dissolved solid content of the samples resulted in a 60 to 80% loss of signal intensity, but were compensated for by using (233)U as an internal standard. Accurate results were obtained with LB-DIHEN-ICP-MS, allowing for the positive identification of depleted uranium based on the (235)U/(238)U ratio. Precision for the (235)U/(238)U ratio is typically better than 5% and 15% for ICP-MS and alpha-spectrometry, respectively, determined over the concentrations and ratios investigated in this study, with the LB-DIHEN-ICP-MS system providing the most accurate results. Short-term precision (6 min) for the individual (235)U and (238)U isotopes in synthetic urine is better than 2% (N = 7), compared to approximately 5% for conventional nebulizer-spray chamber arrangements and >10% for alpha-spectrometry. The significance of these measurements is discussed for uranium exposure assessment of Persian Gulf War veterans affected by depleted uranium ammunitions.

Research paper thumbnail of Atmospheric-pressure helium inductively coupled plasmas for elemental mass spectrometry

Atmospheric-pressure helium inductively coupled plasmas for elemental mass spectrometry

Applied Spectroscopy, 1996

Analytical and fundamental characteristics of helium inductively coupled plasma mass spectrometry... more Analytical and fundamental characteristics of helium inductively coupled plasma mass spectrometry (He ICPMS) were explored for atmospheric-pressure plasmas generated in a 13-mm He ICP torch with the use of a prototype ICPMS equipped with an analogue ...

Research paper thumbnail of Nebulizer diagnostics: fundamental parameters, challenges, and techniques on the horizon

Nebulizer diagnostics: fundamental parameters, challenges, and techniques on the horizon

Journal of Analytical Atomic Spectrometry, 1998

... 1. Would not change key fundamental properties of the plasma: Plasma gas temperature ... or p... more ... 1. Would not change key fundamental properties of the plasma: Plasma gas temperature ... or particles in a polydispersion to acquire an accurate estimate (±5%) of the aerosol parameters listed in Table ... 5 High-speed photographs showing variations in aerosol break-up patterns. ...

Research paper thumbnail of Simulation of droplet heating and desolvation in an inductively coupled plasma — Part I

Spectrochimica Acta Part B-atomic Spectroscopy, 2001

A numerical model is developed to consider for the first time droplet coalescence along with tran... more A numerical model is developed to consider for the first time droplet coalescence along with transport, heating and desolvation in an argon inductively coupled plasma (Ar ICP). The direct simulation Monte Carlo (DSMC) method and the Ashgriz-Poo model are used, respectively, to compute droplet-droplet interactions and to determine the outcome of droplet collisions. Molecular dynamics (MD) simulations support the use of the Ashgriz-Poo coalescence model for small droplet coalescence. Simulations predict spatial maps of droplet number and mass densities within an Ar ICP for a conventional nebulizer-spray chamber arrangement, a direct injection high efficiency nebulizer (DIHEN), and a large bore DIHEN (LB-DIHEN). The primary findings are: (1) even at 1500 W, the collisions of the droplets in the plasma lead primarily to coalescence, particularly for direct aerosol injection; (2) the importance of coalescence in a spray simulation exhibits a complex relationship with the gas temperature and droplet size; (3) DIHEN droplets penetrate further into the Ar ICP when coalescence is considered; and (4) droplets from a spray chamber or the LB-DIHEN coalesce less frequently than those from a DIHEN. The implications of these predictions in spectrochemical analysis in ICP spectrometry are discussed. ᮊ

Research paper thumbnail of Internalization of Carcinogenic Lead Chromate Particles by Cultured Normal Human Lung Epithelial Cells: Formation of Intracellular Lead-Inclusion Bodies and Induction of Apoptosis

Internalization of Carcinogenic Lead Chromate Particles by Cultured Normal Human Lung Epithelial Cells: Formation of Intracellular Lead-Inclusion Bodies and Induction of Apoptosis

Toxicology and Applied Pharmacology, 1999

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead... more Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

Research paper thumbnail of A Large Bore-Direct Injection High Efficiency Nebulizer for Inductively Coupled Plasma Spectrometry

A Large Bore-Direct Injection High Efficiency Nebulizer for Inductively Coupled Plasma Spectrometry

Analytical Chemistry, 2000

A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less pro... more A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less prone to capillary blockage and optimally operates at low nebulizer gas pressures compared with the conventional DIHEN used for inductively coupled plasma (ICP) spectrometries. The aerosol quality is examined using a two-dimensional phase Doppler particle analyzer (2D PDPA), and analytical figures of merits are acquired by ICP mass spectrometry. Compared with the DIHEN, the LB-DIHEN produces larger droplets, but the velocity distributions and mean droplet velocities are narrower and lower, respectively, providing longer residence times for the droplets in the plasma. High RF power (1500 W), low nebulizer gas flow rates (0.25-0.35 L/min), and low solution uptake rates (80-110 microL/min) are required to operate the LB-DIHEN at optimum conditions for ICPMS. Detection limits and sensitivities measured with the LB-DIHEN are superior to those of a conventional nebulizer-spray chamber combination, but precision is inferior. The performance of the LB-DIHEN is further explored in the determination of trace elements in an herbal extract.

Research paper thumbnail of Demountable direct injection high efficiency nebulizer for inductively coupled plasma mass spectrometry

Spectrochimica Acta Part B-atomic Spectroscopy, 2004

A low cost, demountable direct injection high efficiency nebulizer (d-DIHEN) is introduced that p... more A low cost, demountable direct injection high efficiency nebulizer (d-DIHEN) is introduced that provides an adjustable solution capillary, allowing fundamental studies to improve operational characteristics of the micronebulizers, aerosol properties, and analytical figures of merit in inductively coupled plasma (ICP) spectrometries. Similar to the DIHEN and the large bore-DIHEN (LB-DIHEN), the d-DIHEN requires high RF power (1500 W), low nebulizer gas flow rates (approx. 0.16 lymin), and low solution uptake rates (1-100 mlymin) for optimal measurements in ICP mass spectrometry (ICPMS). In contrast to the DIHEN and LB-DIHEN, the optimum position for the d-DIHEN nozzle is located 5 mm (rather than 2 mm) below the end of the torch intermediate tube, thus reducing chances of accidental nebulizer tip meltdown. Compared with the DIHEN, the d-DIHEN produces smaller droplets with narrower droplet distributions and lower mean droplet velocities, characteristics important for improved sample-plasma interaction. Sensitivity, detection limits, and precision are superior with the d-DIHEN compared to conventional nebulizer-spray chamber arrangements and other direct injection nebulizers, especially at low solution uptake rates (-40 mly min). In general, oxide ratios for the d-DIHEN and DIHEN are low and similar at solution uptake rates of 10 mlymin or less. Above 10 mlymin, the d-DIHEN provides lower oxide ratios than the DIHEN. For example, the oxide ratio for Ce increases from 0.6% to 3.8% (d-DIHEN) and 0.5 to 7.6% (DIHEN) as the solution uptake rate is increased from 5 to 85 mlymin. Doubly charged ratios for Ba are also lower for the d-DIHEN at all solution uptake rates compared to the DIHEN. The utility of the d-DIHEN is investigated in the analysis of a reference material (Lyphochek urine metals control) at low (Level 1) and high (Level 2) concentration levels. ᮊ

Research paper thumbnail of Formation and fundamental characteristics of novel free-running helium inductively coupled plasmas

Journal of Analytical Atomic Spectrometry, 2000

This report is the ®rst study on the formation, stabilization and fundamental investigation of fr... more This report is the ®rst study on the formation, stabilization and fundamental investigation of free-running helium inductively coupled plasmas (He ICPs). The plasma was operated at 600±900 W with a total helium gas ow of less than 10 L min 21 . The shape and the physical appearance of free-running helium plasmas differ markedly from the He ICP sources reported previously using a crystal-controlled generator. Although the freerunning helium plasma appears annular, high-speed video studies reveal that the plasma rotates at a frequency of 75±275 Hz. Lateral pro®les of emission spectra of the free-running discharge viewed end-on provide rotational temperature (T rot ), excitation temperature (T exc ), and electron number density (n e ) of 1600±1800 K, 3800±4300 K, and 3.0 to 12610 13 cm 23 , respectively. These fundamental characteristics are compared to those reported previously for crystal-controlled He ICPs and Ar ICPs.

Research paper thumbnail of Direct injection high efficiency nebulizer-inductively coupled plasma mass spectrometry for analysis of petroleum samples

Spectrochimica Acta Part B-atomic Spectroscopy, 2003

Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (... more Direct injection high efficiency nebulizer (DIHEN)-inductively coupled plasma mass spectrometry (ICPMS) is investigated for analysis of petroleum samples dissolved in volatile organic solvents. To minimize solvent loading, the solution uptake rate is reduced to 10 mlymin, far less than the level (85 mlymin) commonly used for aqueous sample introduction with the DIHEN, and oxygen is added to the nebulizer gas flow and outer flow of the ICP. Factorial design is applied to investigate the effect of nebulizer tip position within the torch and the nebulizer and intermediate gas flow rates on the precision and the net signal intensity of the elements tested for multielemental analysis. Cluster analysis and principal component analysis are performed to distinguish the behavior of different isotopes, oxide species and doubly charged ions. The best operating conditions at a solution uptake rate of 10 mly min are: RF powers1500 W, nebulizer gas flow rates0.10-0.12 lymin, intermediate gas flow rates1.5 lymin and DIHEN tip positions3-4 mm below the top of the torch intermediate tube. Acceptable recoveries (100"10%) and good precision (less than 3% relative standard deviation) are obtained for trace elemental analysis in organic matrices (a certified gas oil sample and a custom-made certified reference material) using flow injection analysis. Because of high blank levels, detection limits are 1-3 orders of magnitude higher for organic sample introduction than those acquired for aqueous solutions. ᮊ

Research paper thumbnail of Direct injection high efficiency nebulization in inductively coupled plasma mass spectrometry under cool and normal plasma conditions

Applied Spectroscopy, 2000

The direct injection high ef ciency nebulizer (DIHEN) was investigated for application to inducti... more The direct injection high ef ciency nebulizer (DIHEN) was investigated for application to inductively coupled plasma m ass spectrom etry (ICPMS) with a cool plasma. Elem ents are organized into three categories based on their perform ance in the cool and normal plasma. Sensitivity, precision, and detection limits are presen ted for elem ents ( 39 K, 40 Ca, and 56 Fe) that suffer from m ass spectra l interferences ( 38 ArH 1 , 40 Ar 1 , and 40 Ar 16 O 1 ) derived from the plasma gas. Figures of merit are also reported for a group of elements that are suitable for analysis using either the cool or norm al plasma condition. In a departure from previous published accounts, however, a group of elements is investigated that is suitable for analysis in the cool plasma only by m easurem ent of the metal oxide ion because the sensitivity and precision of the atomic ion are inferior to those obtained for the m etal oxide ion. The sensitivity and precision obtained for these m olecular species are comparable to those obtained for the atomic ions of elem ents that are suitable for analysis using the cool plasma. Calibration curves for the m etal oxide signal as a function of the m etal concentration in the cool plasma are linear over six orders of m agnitude, covering the concentration range from 1 ppt to 1 ppm. Nerve tonic tablets that contain Na, Mg, K , Ca, and Fe in unspeci ed amounts were analyzed under cool plasma conditions. Index Headings: Cool plasm a; Inductively coupled plasma; Inductively coupled plasma mass spectrometry; Direct injection high efciency nebulizer.

Research paper thumbnail of Simulation of droplet heating and desolvation in inductively coupled plasma—part II: coalescence in the plasma

Spectrochimica Acta Part B-atomic Spectroscopy, 2003

A numerical model is developed to consider for the first time droplet coalescence along with tran... more A numerical model is developed to consider for the first time droplet coalescence along with transport, heating and desolvation in an argon inductively coupled plasma (Ar ICP). The direct simulation Monte Carlo (DSMC) method and the Ashgriz-Poo model are used, respectively, to compute droplet-droplet interactions and to determine the outcome of droplet collisions. Molecular dynamics (MD) simulations support the use of the Ashgriz-Poo coalescence model for small droplet coalescence. Simulations predict spatial maps of droplet number and mass densities within an Ar ICP for a conventional nebulizer-spray chamber arrangement, a direct injection high efficiency nebulizer (DIHEN), and a large bore DIHEN (LB-DIHEN). The primary findings are: (1) even at 1500 W, the collisions of the droplets in the plasma lead primarily to coalescence, particularly for direct aerosol injection; (2) the importance of coalescence in a spray simulation exhibits a complex relationship with the gas temperature and droplet size; (3) DIHEN droplets penetrate further into the Ar ICP when coalescence is considered; and (4) droplets from a spray chamber or the LB-DIHEN coalesce less frequently than those from a DIHEN. The implications of these predictions in spectrochemical analysis in ICP spectrometry are discussed. ᮊ

Research paper thumbnail of Computer simulation of argon-nitrogen and argon-oxygen inductively coupled plasmas

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by co... more The properties of mixed-gas At-N2 and Ar-O2 inductively coupled plasmas (ICPs) are obtained by computer simulation. The resuits from the simulations are compared with existing experimental data. The reasons for the deviations are discussed, and inferences are drawn to connect the simulated results to recommendations for practical analytical measurements using ICP atomic emission and ICP mass spectrometries. The effect of the concentration of N2 and 02 in the outer gas flow (0%-100%) and injector gas flow (0%-20%) and the influence of the active power (800-1500 W) on the distribution of the plasma temperatures, electric and magnetic fields and tangential velocity are investigated. In general, mixed-gas plasmas move closer to the state of local thermodynamic equilibrium (LTE) as the concentrations of the molecular gases (N2 and 02) in the outer gas flow are increased. In contrast with the experimental results, the LTE model predicts that mixed-gas plasmas have maximum temperatures (9900-10100 K) comparable with Ar ICPs (10 600 K). The predicted temperature of the mixed-gas plasma is reduced as the concentration of the molecular gas is increased. The temperatures of Ar-O2 ICPs are estimated to be higher than those of Ar-N2 plasmas, except when the outer gas flow contains 100% N2 or 02. © 1997 Elsevier Science B.V.