Abstract: An apparatus for sample concentration for gas chromatography and mass spectrometry for analysis for volatile organic compounds, including a hollow differential pressure switch to switch sample flow non-mechanically, and so that the gas chromatograph and apparatus may be used with different sample levels of volatile organic compounds by changing the timing and temperature parameters by changing the flow non-mechanically.

Abstract: An autosampling device for use in sampling air with canisters and analyzing the contents of said canisters for the presence of pollutants which allows random access of the contents of the canisters and controlled direction of the canister contents to a cryogenic concentrator. The device is a cart having shelf members for holding a plurality of canisters. Sample lines are mounted on the cart to be connectable to a canister at one end of said lines and to an inlet port of an electrically actuated multiposition valve at the other end. To protect against sample disruption, a heated zone around the valve controls valve temperature. An outlet sample line enclosed in a heated zone extends from an outlet port on the valve and is connectable to an inlet of the cryogenic concentrator.