Advantages of on-site monitoring of organic compounds in atmospheric samples by gas chromatography include reduced risk of sample loss and contamination and the potential for lower analysis costs and more rapid response to analysis results. On-site analysis is facilitated by smaller, lighter weight and more autonomous instruments. Greater instrument autonomy has been achieved by the use of ambient air as carrier gas with vacuum-outlet gas chromatography. Micro-fabricated sensors using surface-acoustic-wave or chemiresistor technologies can be made very small and require no additional gas supplies. With in-line sorption-based preconcentrators, detection limits in the low and sub-ppb range can be obtained for 0.1-l.0 L air samples. Series-coupled ensembles of a non-polar and a polar column with independent temperature control provide for several modes of programmable selectivity. Very lightweight, low-power column heating and fast temperature programming are obtained with at-column heating systems in which heat is provided by the current through a wire, which is co-linear with and in close proximity to the fused-silica column. Recently, micro-fabricated GC columns have been used for the separation of volatile organic compounds in large-volume air samples. These columns are etched in silicon chips. The etched channels are doped with boron, and current through the doped layer provides for very low-power column heating. When combined with micro-fabricated preconcentrators and sensor-array detectors, these columns will provide the basis for the development of completely micro-fabricated, autonomous vapor-analysis instruments. Progress in each of the underlying technologies and toward the goal of a wristwatch-size autonomous GC with two-way wireless communication will be presented.
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