Patent ID: 7258132

Claim:
A gas chromatography system, comprising: a sample valve having a vent path and a sample loop that loads a sample before the sample is injected into a column via an inlet, wherein the sample valve has a separate output coupled to the inlet; a back pressure regulator coupled between the vent path and a vent to control and modify pressure in the sample loop during loading and sample injection, further comprising a proportional valve coupled to the vent path and the vent; a pressure sensor coupled to the vent path and coupled to receive a reference pressure to determine pressure in the vent path with respect to the reference pressure; and a closed-loop controller coupled to the pressure sensor and the proportional valve, and coupled to receive a predetermined pressure setpoint, wherein the closed-loop controller controls the proportional valve to regulate a flow through the vent path based on the determined pressure in the vent path and the pressure setpoint so as to control and modify the pressure in the sample loop, and the amount of sample in the sample loop prior to injection of the sample into the column.