Gas chromatograph is an important instrument for separating and measuring the mixed compounds with low boiling point. It is suitable for chemical, food, gas and research analysis.

Gas chromatography analyzes gas substance or substance which can be converted into gas at a certain temperature. Because of different nature of substances, their partition coefficients of each compound are not the same between gas phase and fixative liquid phase. When vaporized sample enters into chromatographic column via carrier gas, its compounds are partitioned several times in two phases. Because of different adsorption and dissolving ability of stationary phase to each compound, although the flow rate of carrier gas is the same, the operation speed of each compound is different in chromatographic column. After a period of time of moving, the compounds are separated each other and enter ino detector in order. After the generated signal is amplified, the recorder will draw up the chromatographic peak of each compound. The name of each compound is identified according to the peak position, and the concentration of each compound is determined by peak area. This is working principle of gas chromatograph.