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

Papers by Akbar Montaser

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

Applied Spectroscopy, 1993

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

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

Research paper thumbnail of 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

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

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

Analytical Chemistry, 2005

Research paper thumbnail of 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

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

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

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

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

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

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

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

Journal of Analytical Atomic Spectrometry, 2000

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

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

Applied Spectroscopy, 2000

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

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

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

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

Applied Spectroscopy, 1993

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

Spectrochimica Acta Part B-atomic Spectroscopy, 1997

Research paper thumbnail of 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

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

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

Analytical Chemistry, 2005

Research paper thumbnail of 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

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

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

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

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

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

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

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

Journal of Analytical Atomic Spectrometry, 2000

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

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

Applied Spectroscopy, 2000

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

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

Spectrochimica Acta Part B-atomic Spectroscopy, 1997