STEPPER MOTOR CONTROLLED MICRO GAS VALVE INLET SYSTEM FOR GAS-CHROMATOGRAPHY

A novel gas valve inlet system for gas chromatography is described. Th e device incorporates a capillary sample gas delivery tube containing a small orifice in its side from which sample vapor continuously flows . A precision micro stepper motor is used to translate the sample deli very tube parallel to its axis so that the orifice passes by the end o f the fused silica separation column. The inlet end of the column and the sample delivery tube are housed in a pressurized injection port wh ich also contains purge flows to vent sample between injections. Two o perating modes are described. In the sweep mode, the orifice sweeps pa st the column end at a constant, adjustable velocity. In the park mode , the orifice is parked in front of the column end for a software sele ctable time. Injection sample size and bandwidth are adjustable. Bandw idths (a) as small as a few milliseconds make the inlet suitable for h igh-speed gas chromatography as well as conventional GC.