The principle and use of gas chromatograph

principle

Gas chromatography uses gas as the mobile phase (carrier gas). When the sample is "injected" into the injector by the microsyringe, it is carried by the carrier gas into the packed column or capillary chromatography column. Due to the difference in distribution or adsorption coefficient of each component in the sample between the mobile phase (gas phase) and the stationary phase (liquid phase or solid phase) in the chromatographic column, under the flushing of the carrier gas, each component repeatedly moves between the two phases. Sub-distribution separates each component in the column, and then uses a detector connected after the column to detect each component in order according to the physical and chemical properties of the components [1].

The signal given by the detector for each component appears as peaks on the recorder, called chromatographic peaks. The maximum value on the chromatographic peak is the basis for qualitative analysis, while the area covered by the chromatographic peak depends on the content of the corresponding component, so the peak area is the basis for quantitative analysis. After a mixture sample is injected, the curve recorded by the recorder is called a chromatogram. Qualitative and quantitative analysis results can be obtained by analyzing the chromatogram.

Instructions

The general analysis process of a gas chromatograph: the carrier gas flows out from the high-pressure cylinder. After being reduced to the required pressure by the pressure reducing valve, the carrier gas is purified through the purification drying tube. Pressure and constant velocity flow through the vaporization chamber to mix with the vaporized sample, and the sample gas is substituted into the chromatographic column for separation. The separated components flow into the detector one after another along with the carrier gas, and then the carrier gas is vented. The detector converts the change in concentration or mass of the substance into a certain electrical signal, which is amplified and recorded on the recorder to obtain the chromatographic outflow curve. Qualitative analysis can be performed based on the retention time of each peak obtained on the chromatographic elution curve, and quantitative analysis can be performed based on the peak area or peak height.