The analysis or preparative isolation of a specimen by a packed column gas chromatograph is affected by the kind and amount (concentration) of the liquid phase coated on the stationary phase. In particular, compounds having the same or similar molecular weight and similar functional groups are largely affected. Methyl oleate, which is a typical component of fats and oils, produces hydroperoxide by air oxidation as a first step. After that, various oxygenated compounds with a carbon number of 19 are produced. In this study, the effect of the concentration of ethylene glycol succinate polyester (EGS) as the liquid phase was examined for these compounds. The retention time of the hydroxides increased with an increase in the EGS concentration. The effect of the EGS concentration on the retention time decreased when these compounds were trimethyl silylated (TMS). The retention time of epoxides and oxo compounds increased with an increase in the EGS concentration independently of trimethyl silylation. Correction values were required for all quantitation.