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Direct Sampling Ion Trap Mass Spectrometer (DSITMS)

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Tech ID: 69
Project Overview
Direct Sampling Ion Trap Mass Spectrometry (DSITMS) introduces sample materials directly into an ion trap mass spectrometer by means of a very simple interface, such as a capillary restrictor or a polymer membrane, with little if any sample preparation and no chromatographic separation of sample constituents. Target analytes include Volatile Organic Constituents (VOCs) and selected SemiVolatile Organic Constituents (SVOCs). Instrument analysis is nearly instantaneous; analyses are typically completed in less than five minutes at cost typically less than half that of standard EPA Method analyses performed in commercial laboratories. DSITMS can be used in conjunction with Cone Penetrometer sampling methods.
Technology Description
DSITMS introduces sample materials directly into an ion trap mass spectrometer through a very simple interface with little if any sample preparation and no chromatographic separation of sample constituents. Target analytes include Volatile Organic Constituents (VOCs) and seleced SemiVolatile Organic Constituents (SVOCs). VOCs in water are introduced by purging the sample with helium and routing the purge stream to the DSITMS. VOCs in air, soil gas, and water can be measured in real time; alternately, they may be captured in sorbent traps and subsequently analysed by thermal desorbtion into the DSITMS. Instrument analysis is nearly instantaneous; analyses are typically completed in less than five minutes at cost typically less than half that of standard EPA Method analyses performed in commercial laboratories. Detection limits are well within the range required by EPA, typically 1-5 ppb for VOCs in water and soils and 1-100 ppbv for continuous monitoring of air. Because there is no chromatographic separation of constituents, interferences may limit the ability to reliably quantitate some constituents of concern (COCs) in complex mixtures. This is not a problem in field applications in which the major COCs are known from historical data. Also, this does not limit the usefulness of DSITMS in field screening to determine the spatial extent of contamination; the low detection limits effectively exclude false negatives in concentration ranges of interest.

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