CRYOFOCUSING INLET WITH REVERSE FLOW SAMPLE COLLECTION FOR GAS-CHROMATOGRAPHY

An inlet system for high-speed gas chromatography is characterized. Sa mple is cryofocused in a bare metal capillary tube and released by a f ast temperature increase caused by an electric current. The gas flow d irection through the capillary tube is reversed after sample collectio n so that the sample injection onto the capillary column for separatio n occurs from the downstream end of the metal tube. The system offers narrower initial band widths, elimination of memory effects, and reduc ed thermal decomposition during reinjection relative to previously des cribed cryofocusing inlet systems. Sample vapor can be collected and c ryofocused from any source pressure greater than approximately 20 Torr . A configuration for direct air sampling is described.