The basic components of a gas chromatograph are a gas system, a sampling system, a separation system, a detection system, and a recording system. GC has the characteristics of high separation efficiency, high selectivity, high sensitivity, fast speed and wide application. Also known as color layer, analysis, layering, etc., Refers to the separation and analysis method of separating a mixture into individual components. Because of its high separation efficiency, fast analysis speed and high detection sensitivity, it is an important separation analysis technology and physical and chemical research method. Because of its wide application and simple operation, it is widely used in production, scientific research, teaching and many other fields, especially after combining with computer, it has become an indispensable means of analysis, detection, separation, purification and so on.

The separation principle of the GC method is to use the various components in the mixture to have different dissolution and analysis capabilities in the mobile phase and the stationary phase. When the two phases move, the difference between the adsorption-desorption forces or other affinities causes each component in the sample to repeat multiple times (≥ 103 times) in the two phases, separating the mixed components from each other.

After the sample (including A, B, A, B mixture) enters the chromatographic column, the mobile phase brings the sample into the chromatographic column. When entering the column, the components A and B will have mixed bands.

Differences in the dissolution-resolution, adsorption-desorption, or other affinities of each component in the stationary phase result in different residence times of each component in the column, I .e., their residence times in the column are also different. As the mobile phase continues to flow, each component undergoes multiple partitioning and equilibration processes between the two phases in the column. With a certain column length, each component in the sample is separated. When component A leaves the outlet of the chromatographic column, the chromatographic peak of component A is recorded by the detector; when component B leaves the chromatographic column and flows through the detector, the recording device records the chromatographic peak of component B.

In the gas chromatographic column, due to the influence of eddy diffusion, molecular diffusion (vertical diffusion), mass transfer resistance and other factors, the recorded chromatographic peaks do not appear on the rectangular spectral band, but appear on the chromatographic peaks close to the Gaussian distribution curve.