The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform

John S Beale - One of the best experts on this subject based on the ideXlab platform.

  • vapor extraction experiments with laboratory soil columns implications for field programs
    Waste Management, 1991
    Co-Authors: Peter M Kearl, Nic Korte, T A Gleason, John S Beale
    Abstract:

    Abstract As part of a site remediation project, laboratory soil column experiments were conducted to evaluate the effectiveness of a field vapor extraction system. Different soil types were placed in specially designed soil columns and saturated with 1,1,1-Trichloroethane and Jet-A fuel. The soil columns were connected to a vacuum pump and removal rates were monitored using mass balance, a portable Photoionization Detector, and a gas chromatograph. Results of the laboratory experiments indicated that the technique is useful for designing and monitoring field vapor extraction systems. Guidelines were developed for flow rate versus removal times, the effects of varying lithologies on removal rates and efficiencies, and the removal characteristics of organic mixtures consisting of varying volatile components.

Masatoshi Morita - One of the best experts on this subject based on the ideXlab platform.

Peter M Kearl - One of the best experts on this subject based on the ideXlab platform.

  • vapor extraction experiments with laboratory soil columns implications for field programs
    Waste Management, 1991
    Co-Authors: Peter M Kearl, Nic Korte, T A Gleason, John S Beale
    Abstract:

    Abstract As part of a site remediation project, laboratory soil column experiments were conducted to evaluate the effectiveness of a field vapor extraction system. Different soil types were placed in specially designed soil columns and saturated with 1,1,1-Trichloroethane and Jet-A fuel. The soil columns were connected to a vacuum pump and removal rates were monitored using mass balance, a portable Photoionization Detector, and a gas chromatograph. Results of the laboratory experiments indicated that the technique is useful for designing and monitoring field vapor extraction systems. Guidelines were developed for flow rate versus removal times, the effects of varying lithologies on removal rates and efficiencies, and the removal characteristics of organic mixtures consisting of varying volatile components.

Masoud Agah - One of the best experts on this subject based on the ideXlab platform.

  • gc on chip integrated column and Photoionization Detector
    Lab on a Chip, 2015
    Co-Authors: Muhammad Akbar, Hamza Shakeel, Masoud Agah
    Abstract:

    This paper reports a unique GC-on-chip module comprising a monolithically integrated semi-packed micro separation column (μSC) and a highly sensitive micro helium discharge Photoionization Detector (μDPID). While semi-packed μSC with atomic layer deposited (ALD) alumina as a stationary phase provides high separation performance, the μDPID implemented for the first time in a silicon–glass architecture inherits the desirable features of being universal, non-destructive, low power consumption (1.4 mW), and responsive. The integrated chip is 1.5 cm × 3 cm in size and requires a two-mask fabrication process. Monolithic integration alleviates the need for transfer lines between the column and the Detector which improves the performance of the individual components with overall reduced fabrication and implementation costs. The chip is capable of operating under the isothermal as well as temperature and flow programming conditions to achieve rapid chromatographic analysis. The chip performance was investigated with two samples: 1) a multi-analyte gas mixture consisting of eight compounds ranging from 98 °C to 174 °C in boiling point and 2) a mixture containing higher alkanes (C9–C12). Our experiments indicate that the chip is capable of providing rapid chromatographic separation and detection of these compounds (<1 min) through the optimization of flow and temperature programming conditions. The GC-on-chip demonstrated a minimum detection limit of ~10 pg which is on a par with the widely used destructive flame ionization Detector (FID).

  • GC-on-chip: integrated column and Photoionization Detector
    Lab on a Chip, 2015
    Co-Authors: Muhammad Akbar, Hamza Shakeel, Masoud Agah
    Abstract:

    This paper reports a unique GC-on-chip module comprising a monolithically integrated semi-packed micro separation column (μSC) and a highly sensitive micro helium discharge Photoionization Detector (μDPID). While semi-packed μSC with atomic layer deposited (ALD) alumina as a stationary phase provides high separation performance, the μDPID implemented for the first time in a silicon–glass architecture inherits the desirable features of being universal, non-destructive, low power consumption (1.4 mW), and responsive. The integrated chip is 1.5 cm × 3 cm in size and requires a two-mask fabrication process. Monolithic integration alleviates the need for transfer lines between the column and the Detector which improves the performance of the individual components with overall reduced fabrication and implementation costs. The chip is capable of operating under the isothermal as well as temperature and flow programming conditions to achieve rapid chromatographic analysis. The chip performance was investigated with two samples: 1) a multi-analyte gas mixture consisting of eight compounds ranging from 98 °C to 174 °C in boiling point and 2) a mixture containing higher alkanes (C9–C12). Our experiments indicate that the chip is capable of providing rapid chromatographic separation and detection of these compounds (

  • A micro-discharge Photoionization Detector for micro-gas chromatography
    Microchimica Acta, 2014
    Co-Authors: Shree Narayanan, Gary Rice, Masoud Agah
    Abstract:

    We report on a small (20 × 10 mm) micromachined device for the detection of gases in micro-gas chromatography (GC). It incorporates a micro-discharge across a 20-μm gap, and a remote electrode in the micro cavity that generates an electrical signal corresponding to the photo-ionization of gaseous analytes in a stream of carrier gas. Multi-component mixtures were detected and the results compared to those obtained with a flame ionization Detector. The minimum detectable limit is 350 pg.μL^−1 of n-octane in air when applying a 1.4 mW discharge. The combination of wet etching of glass (as used for microfluidic channels) with a lift-off process for Detector electrodes by a robust batch process results in a universal, non-destructive, and sensitive microDetector for micro-GC. Figure ᅟ

  • A micro-discharge Photoionization Detector for micro-gas chromatography
    Mikrochimica Acta, 2014
    Co-Authors: Shree Narayanan, Gary W. Rice, Masoud Agah
    Abstract:

    We report on a small (20 × 10 mm) micromachined device for the detection of gases in micro-gas chromatography (GC). It incorporates a micro-discharge across a 20-μm gap, and a remote electrode in the micro cavity that generates an electrical signal corresponding to the photo-ionization of gaseous analytes in a stream of carrier gas. Multi-component mixtures were detected and the results compared to those obtained with a flame ionization Detector. The minimum detectable limit is 350 pg.μL−1 of n-octane in air when applying a 1.4 mW discharge. The combination of wet etching of glass (as used for microfluidic channels) with a lift-off process for Detector electrodes by a robust batch process results in a universal, non-destructive, and sensitive microDetector for micro-GC.

  • A micro helium-discharge Photoionization Detector for gas sensing
    2013 IEEE SENSORS, 2013
    Co-Authors: Shree Narayanan, Masoud Agah, Gary W. Rice
    Abstract:

    This paper reports a 2cm × 1cm easy-to-micromachine helium discharge Photoionization Detector (μHeDPID) for use in micro gas chromatography by utilizing a lift-off process. This universal Detector consumes a miserly 2.5mW for plasma generation and non-destructively photoionizes analyte compounds, thus avoiding fouling of electrodes. The ionized species is detected by a remote electrode connected to a picoammeter. The Detector exhibits at least 350pg and 50ppm detection limit for n-octane in air. Despite the Detector simplicity, its efficiency is in par with previously reported destructive plasma Detectors which are based on more sophisticated spectrometric analysis.

Stanley D. Stearns - One of the best experts on this subject based on the ideXlab platform.

  • Characterization of chlorinated compounds using a dual chlorine-selective pulsed discharge emission Detector-helium-pulsed discharge Photoionization Detector system.
    Journal of Chromatography A, 2000
    Co-Authors: Kefu Sun, Wayne E. Wentworth, Stanley D. Stearns
    Abstract:

    Abstract The Cl-selective pulsed discharge emission Detector (Cl-PDED) response is dependent only upon the Cl content, irrespective of the molecular structures of the compounds. This provides a simple, fast quantitative method of analysis for chlorinated compounds. The response of the helium-pulsed discharge Photoionization Detector (He-PDPID) is a function of the molecular structure and the number of photoionizable electrons using the He2 band at 13.5–17.5 eV. The ratio of the responses of the two Detectors is independent of concentration and can be used to characterize the Cl-containing compounds along with the retention time, or the ratio can be used as evidence for coelution. The dual Cl-PDED–He-PDPID Detector system is a useful tool for peak identification. The effect of coeluting hydrocarbons on the Cl-PDED response was evaluated by spiking a gasoline sample with US Environmental Protection Agency mixture 502. All Cl-PDED responses were greater than 90% of the response in the absence of the hydrocarbons.

  • A Unique Qualitative GC Experiment for an Undergraduate Instrumental Methods Course Using Selective Photoionization Detectors
    Journal of Chemical Education, 1998
    Co-Authors: Justin M. Notestein, Wayne E. Wentworth, Edward C. M. Chen, Nadege Helias, Julie G. Dojahn, Stanley D. Stearns
    Abstract:

    In this experiment designed for the undergraduate instrumental analysis laboratory, a pulsed discharge Photoionization Detector (PDPID) is used to efficiently differentiate between and qualitatively identify 12 compounds in a sample mixture. This is accomplished using benzene as an internal standard and by correlating the relative responses of the 11 organic compounds in a He, Ar, and Kr PDPID with their relative retention times. This method is designed to be safe, relatively inexpensive, virtually nondestructive, and highly sensitive.

  • Relative responses of various classes of compounds using a pulsed discharge helium Photoionization Detector experimental determination and theoretical calculations
    Journal of Chromatography A, 1996
    Co-Authors: Sanford Mendonca, Wayne E. Wentworth, Edward C. M. Chen, Stanley D. Stearns
    Abstract:

    Abstract The relative response factors for 174 compounds have been determined using a helium pulsed discharge Photoionization Detector. The values were obtained with a relative standard deviation that ranged to 4.3% with a median of 1%. The mean values of the relative mass response factors ranged from 0.26 to 1.18. If the Detector is not calibrated and equal response factors are assumed, a potential error of ± 32% could be expected. The SCF molecular orbitals of these same molecules were calculated and used to determine the number of ionizable electrons based upon the He2 continuous emission. The molar response of the compounds and the number of ionizable electrons are well correlated.

  • Experimental and theoretical relative response factors for a pulsed discharge krypton Photoionization Detector
    Journal of Chromatography A, 1996
    Co-Authors: Wayne E. Wentworth, Edward C. M. Chen, Nadege Helias, Robert Swatloski, Sarasak Watanesk, Stanley D. Stearns
    Abstract:

    The relative Photoionization cross sections (RePIX) have been determined for a series of compounds normalized to benzene. The Detectors are doped (5.01% Kr) Kr-PDPID and pure helium(He-PDPID) pulsed discharge helium Photoionization Detectors. The pure helium Detector is used to reference the responses. The magnitudes for the Kr-PDPID varied from about 0.0 to 0.95. In order to understand the relative responses of these compounds in the Kr-PDPID, the SCF-MO energy levels were calculated for these compounds using HyperChem. Calculated vertical ionization potentials are compared with experimental adiabatic ionization potentials.

  • Windowless pulsed-discharge Photoionization Detector application to qualitative analysis of volatile organic compounds
    Journal of Chromatography A, 1996
    Co-Authors: Gerard Gremaud, Wayne E. Wentworth, Edward C. M. Chen, Albert Zlatkis, Robert Swatloski, Stanley D. Stearns
    Abstract:

    Abstract The effluent from a gas chromatograph was split and directed to four identical windowless Photoionization Detectors. These Detectors use pure helium, helium with Ar (0.64%), Ar (4.15%) and Kr (0.58%) as the discharge gas. The relative ionization cross-sections can be obtained from the ratio of the normalized response using an internal standard. This value is characteristic of the compound and could be used for qualitative analysis. These ratios for 47 compounds encompassing 13 functional groups have been determined and are reported. The values have an average relative standard deviation of 2% for the majority of the compounds. The long-term reproducibility of a smaller set of compounds has been determined and was 0.78–2% relative standard deviation for the Ar Detector and 5.6–11.3% (worse cases) where the response of the krypton Detector is low.