Laboratory evaluation of a prototype portable gas chromatograph (GC) with a flame ionization detector (FID) for toluene, ethylbenzene, and xylenes (TEX) analysis

Abstract The standard method to evaluate human exposure to volatile organic compounds (VOCs) is in general performed by sampling the air on sorbents followed by liquid extraction and detection using laboratory gas chromatograph (GC). The conventional method is time and labor intensive and employs a toxic solvent which adds a risk factor as well as waste. Hence, there have been increasing demands for portable GC instruments which allow near real-time, in-situ analysis. In this study, the potential use of a prototype, dual column portable GC (protoGC) with flame ionization detector (FID) was examined by comparing its performance with a conventional GC laboratory method. Four target concentration levels (1x, 2x, 4x, and 8x; x = 1.12 ± 0.01 ppm) of toluene, ethylbenzene, and o-, m-, and p-xylene were generated in an exposure chamber (24 ± 1 °C and 50 ± 5% RH). The challenge atmosphere was directly sampled and analyzed with protoGC while for the conventional method it was sampled on a sorbent tube and analyzed with a laboratory GC/FID. The results of protoGC correlated well with the conventional method (r = 0.991–0.999), indicating that protoGC has comparable performance with the conventional method within the test conditions. Although two-way ANOVA showed significant differences in mean concentrations between the methods, the differences were small. protoGC would be useful to monitor VOCs in air with high temporal resolution or to quickly determine the safety of the environment of interest due to the substantial time savings in sampling and analysis. Further examinations at various environmental conditions and other analytes will be necessary to thoroughly evaluate its performance

A Portable Universal Hazardous Gas Detector

Experimental work on the Miniature Mass Spectrometer (MMS) at JPL has resulted in a 'table top' configuration with a CCD detector that has demonstrated a detection limit of 50 parts per billion. The CCD detector operates at ambient temperature. Intelligent Ion, Inc., a commercial instrument developer, has taken out a license on the JPL technology and has built a prototype using a Faraday Cup Array detector as a placeholder detector. The prototype instrument was tested at Kennedy Space Center and demonstrated detection limits in the parts per million range. The test results are presented as well as detailed photographs of the prototype instrument. A presentation of the MMS was made to an expert review panel for 'On-Board Environmental Monitoring Systems for the International Space Station (ISS).' The scores obtained by the MMS system are presented. The prototype instrument will be retro fitted with a CCD array detector in August 2004 and will again be tested at KSC. The instrument is expected to show a detection level for hydrazines of 10 ppb and a detection level for solvents below 10 ppb.The expectations are based on raw data from the first batch of CCD's that was tested

Field-deployed Underwater Mass Spectrometers for Investigations of Transient Chemical Systems

The mass spectrometer developments and underwater deployments described in this work are directed toward observations of important reactive and influential inorganic and organic chemicals. Mass spectrometer systems for measurement of dissolved gases and volatile hydrocarbons were created by coupling a membrane analyte-introduction system with linear quadrupole and ion trap mass analyzers. For molecular masses up to 100 amu, the in situ quadrupole system has detection limits on the order of 1–5 ppb. For masses up to approximately 300 amu, the underwater ion trap system detects many volatile hydrocarbons at concentrations below 1 ppb. Both instruments can function autonomously or via interactive communications from a remote control site. Continuous operations can be sustained for up to approximately 12 days. Deployments have initially involved shallow water proof-of-concept operations at depths less than 30 m. Future modifications are planned that will allow operational depths to 200 m

Detection and Quantification of Chemical Plumes Using a Portable Underwater Membrane Introduction Mass Spectrometer

Application of in situ membrane introduction mass spectrometry (MIMS) to quantification of aqueous chemicals was evaluated in the laboratory and the field. Laboratory experiments were performed to examine the influence of sampling parameters on mass-resolved time-series data. Results were applied to field data to quantify concentrations in a chemical plume

IonCCD Detector for Miniature Sector-Field Mass Spectrometer:Investigation of Peak Shape and Detector Surface Artifacts Induced by keV Ion Detection

A recently described ion charge coupled device detector IonCCD (Sinha and Wadsworth, Rev. Sci. Instrum. 76(2), 2005; Hadjar, J. Am. Soc. Mass Spectrom. 22(4), 612-624, 2011) is implemented in a miniature mass spectrometer of sector-field instrument type and Mattauch-Herzog (MH)-geometry (Rev. Sci. Instrum. 62(11), 2618-2620, 1991; Burgoyne, Hieftje and Hites J. Am. Soc. Mass Spectrom. 8(4), 307-318, 1997; Nishiguchi, Eur. J. Mass Spectrom. 14(1), 7-15, 2008) for simultaneous ion detection. In this article, we present first experimental evidence for the signature of energy loss the detected ion experiences in the detector material. The two energy loss processes involved at keV ion kinetic energies are electronic and nuclear stopping. Nuclear stopping is related to surface modification and thus damage of the IonCCD detector material. By application of the surface characterization techniques atomic force microscopy (AFM) and X-ray photoelectrons spectroscopy (XPS), we could show that the detector performance remains unaffected by ion impact for the parameter range observed in this study. Secondary electron emission from the (detector) surface is a feature typically related to electronic stopping. We show experimentally that the properties of the MH-mass spectrometer used in the experiments, in combination with the IonCCD, are ideally suited for observation of these stopping related secondary electrons, which manifest in reproducible artifacts in the mass spectra. The magnitude of the artifacts is found to increase linearly as a function of detected ion velocity. The experimental findings are in agreement with detailed modeling of the ion trajectories in the mass spectrometer. By comparison of experiment and simulation, we show that a detector bias retarding the ions or an increase of the B-field of the IonCCD can efficiently suppress the artifact, which is necessary for quantitative mass spectrometry