Abstract: The 10 g of cough syrup sample was taken, 10.0 mL of water was added for initial dissolution, and then 3.0 g of sodium chloride and 10 mL of n-hexane were added. The mixture was mixed evenly by vortex and centrifuged for 5 min. The n-hexane layer was discarded, and 20 mL of ethyl acetate was added into the retention layer. The mixture was mixed evenly and centrifuged for 5 min, and the supernatant was collected. The 20 mL of ethyl acetate was added into the residue, and the extraction process was repeated once. The supernatant was combined, and blown to near dryness by nitrogen at 35 ℃. The 1.0 mL of acetone was added to dissolve the residue, and the mixed solution was passed through a 0.22 μm filter membrane. The filtrate was introduced into the gas chromatograph at a split ratio of 10∶1. Five chemical pollutants, including ethylene glycol, diethylene glycol, 4-methylimidazole, 1-methylimidazole, and 2-methylimidazole, were separated on an HP-INNOWAX capillary chromatographic column using a heating program, detected by a hydrogen flame ionization detector, and quantified by the external standard method. It was shown that linear relationships between values of the mass concentrations and peak areas of the 5 chemical pollutants were kept in the range of 1.0-100 mg·L⁻¹, with detection limits (3S/N) in the range of 0.05-0.08 mg·kg⁻¹. Test for recovery was made by the standard addition method, giving recoveries in the range of 85.0%-98.5%, and RSDs (n=6) of the determined values were all less than 10%. The proposed method was used for the analysis of 15 batches of actual samples, and 4-methylimidazole was detected in 2 batches of samples, with detection amounts of 0.10, 0.11 mg·kg⁻¹, respectively.