Abstract: On the basis of vapour pressure changes at the inlet and outlet of a gas chromatographic column and the vapour pressure values of six types of compounds with different carbon atoms at diffferent temperatures, the basic conditions for using gas chromatography to analyze a component have been obtained. It appears that the vapour pressure of a component must be higher than 15～746Pa,and the capacity factor in the range of 0.2～20. A large retention value may prevent a component from being analyzable by gas chromatography. When the capacity factor (k′) of a component lies in the range of 0.2 to 20,its vapour pressure will meet the requirements of FID detection.

Key words: gas chromatography, detection limit, elution limit, restricting factor