Abstract: A method for the determination of residual dichloromethane and trichloromethane in ranitidine hydrochloride by headspace liquid phase microextraction coupled with gas chromatography （GC） was developed. A homemade device was used to protect the organic drop. The effects of the nature of extraction solvent, extraction time, extraction temperature and microdrop volume on the extraction efficiency were investigated separately. The optimal experimental conditions were as follows: 2 μL of n-tridecane as extraction solvent, 30 min of extraction time, 60 ℃ of extraction temperature. The correlation coefficients of linear calibration curve were 0.9733 and 0.9724 within the concentration ranges of dichloromethane (1~10 μg/g) and trichloromethane (1~10 μg/g), respectively. The detection limits of dichlormethane and trichloromethane were 0.0273 μg/g and 0.0410 μg/g, respectively, the relative standard deviations were lower than 4.36% and 5.89%, and the recoveries of the method were 93.6%~102% and 98.1%~103%, respectively. The method is simple and reliable.

Key words: dichloromethane, gas chromatography （GC）, ranitidine hydrochloride , trichloromethane, liquid phase microextraction