Current Instrumentation for Field-Deployable Analysis of Organic Compounds

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Current Instrumentation for Field-Deployable Analysis of Organic Compounds

Overton, E. B. / Collard, E. S. / Dharmasena, H. P. / Klinkhachorn, P. / Sherman, R. W.

A field-deployable microchip gas chromatograph with high resolution capillary column separating capabilities has been linked to an external microcomputer. The instrument system produces rapid, high quality field analyses of volatile organic compounds in both ambient air and water samples with an analysis time of approximately two minutes. The newest version of the instrument system actually analyzes samples simultaneously on two capillary columns, each coated with a different liquid phase. This correlations chromatographic technique allows for a much higher degree of accuracy in compound identification than is obtainable with single capillary column analyses. A modified, temperature independent Kovats retention index system, in which the retention times of the reference compounds are calculated at ambient temperature rather than measured, eliminates the need for standard gases in the field and minimizes the need for temperature control. Telemetry techniques provide the capability to operate the microchip gas chromatograph at field locations while chromatographic data are analyzed by a chemist in a central laboratory if necessary.As a modular part of this analytical system, a portable sorption tube concentration device has been developed to increase the overall sensitivity of the analytical procedure. Additionally, the same concentrator may also be used to analyze for volatile organic compounds in water samples using a “purge and trap” technique. Detection limits are in the 10 ppb range for ambient air samples and 1 ppb range for water samples.