Gas chromatography with ambient pressure stability control
View Patent ↗In a gas chromatography apparatus, a carrier gas is flowed from a carrier gas supply toward an analytical column at a carrier gas pressure. A sample is added to the carrier gas to form a sample gas. The sample gas is flowed through the analytical column to a gas detector that includes a sample gas outlet communicating with a gas buffer vessel. The carrier gas pressure is controlled relative to a buffer pressure of the gas buffer vessel.
1. A gas chromatography apparatus, comprising:
an analytical column;
a sample gas introduction device communicating with the analytical column;
a gas pressure controller comprising a carrier gas inlet, a carrier gas outlet communicating with the sample gas introduction device and a gas pressure reference outlet;
a gas detector comprising a sample gas inlet communicating with the analytical column and a sample gas outlet;
a gas buffer vessel communicating with the gas pressure reference outlet and the sample gas outlet, the gas buffer vessel comprising a gas buffer outlet; and
a gas outlet valve configured for switching the gas buffer outlet between an open condition in a period during which an acquisition of chromatographic data is not desired, in which open condition the pressure controller, the detector and the gas buffer vessel are in fluid communication with an ambient environment surrounding the gas chromatography apparatus, and a closed condition during a run of a chromatography experiment, in which closed condition the pressure controller, the detector and the gas buffer vessel are fluidly isolated from the ambient environment.
2. The gas chromatography apparatus of claim 1 , further comprising a reference column, wherein the carrier gas outlet of the gas pressure controller comprises a first carrier gas outlet communicating with the analytical column and a second carrier gas outlet communicating with the reference column, and the gas detector further comprises a reference gas inlet communicating with the reference column and a reference gas outlet communicating with the gas buffer vessel.
3. The gas chromatography apparatus of claim 1 , wherein the gas detector is a thermal conductivity detector.
4. The gas chromatography apparatus of claim 1 , further comprising a system controller communicating with the gas outlet valve and configured for actuating the gas outlet valve between the open and closed conditions in coordination with controlling the sample introduction device.
5. A method for operating a gas chromatography apparatus, the method comprising:
flowing a carrier gas from a carrier gas supply toward an analytical column at a carrier gas pressure;
adding a sample to the carrier gas to form a sample gas;
flowing the sample gas through the analytical column to a gas detector, the gas detector comprising a sample gas outlet communicating with a gas buffer vessel; and
controlling the carrier gas pressure relative to a buffer pressure of the gas buffer vessel, wherein controlling the carrier gas pressure comprises switching a gas outlet valve of the gas buffer vessel from an open position in a period during which an acquisition of chromatographic data is not desired to a closed position during a run of a chromatography experiment, wherein at the open position the detector and the gas buffer vessel are in fluid communication with an ambient environment external to the gas chromatography apparatus, and at the closed position the detector and the gas buffer vessel are fluidly isolated from the ambient environment.
6. The method of claim 5 , wherein controlling the carrier gas pressure comprises operating a gas pressure controller interposed between the carrier gas supply and the analytical column and communicating with the gas buffer vessel as to use the buffer pressure as reference pressure.
7. The method of claim 5 , wherein controlling the carrier gas pressure comprises operating a gas pressure controller interposed between the carrier gas supply and the analytical column and communicating with the gas buffer vessel as to use the buffer pressure as reference pressure, and venting sample gas from the sample gas outlet to the gas buffer vessel.
8. The method of claim 5 , wherein controlling the carrier gas pressure comprises operating a gas pressure controller interposed between the carrier gas supply and the analytical column and communicating with the gas buffer vessel as to use the buffer pressure as reference pressure, and fluidly isolating the pressure controller, the gas detector and the gas buffer vessel from an ambient environment external to the gas chromatography apparatus.
9. The method of claim 5 , further comprising permitting the buffer pressure to increase above an ambient pressure of the ambient environment while the gas outlet valve is in the closed position.
10. The method of claim 5 , further comprising ceasing the flow of sample gas through the analytical column, and switching the gas outlet valve from the closed position to the open position.
11. The method of claim 5 , further comprising switching the gas outlet valve in timed coordination with flowing the carrier gas and adding the sample.
12. The method of claim 5 , further comprising flowing the carrier gas from the carrier gas supply through a reference column and to the gas detector.
13. The method of claim 5 , further comprising flowing the carrier gas from the carrier gas supply through a reference column and to the gas detector, wherein controlling the carrier gas pressure comprises operating a gas pressure controller to control respective carrier gas flows from the carrier gas supply to the analytical column and to the reference column, venting sample gas from the sample gas outlet to the gas buffer vessel, and venting reference gas from a reference gas outlet of the gas detector to the gas buffer vessel.
14. The method of claim 5 , further comprising operating the gas detector by measuring a thermal conductivity of the sample gas.