Determination of 62 Organic Pollutants in Drinking Water by Gas Chromatography-Tandem Mass Spectrometry with Solid Phase Extraction/Liquid-Liquid Extraction

The treated drinking water sample （1 L） was taken and placed in a fully automatic solid phase extraction instrument. The solid phase extraction column was sequentially rinsed with 5 mL of dichloromethane and 5 mL of ethyl acetate, and sequentially activated with 10 mL of methanol and 10 mL of water. Sample was loaded at a flow rate of 10 mL·min⁻¹. The solid phase extraction bottle was washed with 50 mL of water, and the washing solution was also loaded. After being drained, the solid phase extraction column was dried with nitrogen for 5 min, then sequentially eluted with 5 mL of methanol, 4 mL of ethyl acetate, 4 mL of the mixed solution of ethyl acetate and dichloromethane at a volume ratio of 1∶1, and 8 mL of dichloromethane, and the eluate was collected. Alternatively, 1 L of treated drinking water sample （pH 6‒7） was taken, and extracted with 30 mL of dichloromethane for 5 min. The organic phase was collected, and the extraction was repeated once. The pH of the aqueous phase was adjusted to no more than 2 with 50% （volume fraction） hydrochloric acid solution, and 30 mL of the mixed solution of dichloromethane and ethyl acetate at a volume ratio of 1∶1 was added for extraction. All organic phases were combined and dehydrated with anhydrous sodium sulfate. Then, 5 mL of the mixed solution of ethyl acetate and cyclohexane at a volume ratio of 1∶1 was added, and the mixture was concentrated to 1.0 mL by nitrogen at 35 ℃. The solution was purified by a Bio-Beads S-X3 gel chromatographic column, and the purified solution was collected. The eluate or purified solution was concentrated to near dryness by nitrogen at 35 ℃. 10 µL of 10 mg·L⁻¹ mixed isotope internal standard working solution was added, and the volume was made up to 1.0 mL with dichloromethane. The 62 organic pollutants in the solution was determined by gas chromatography-tandem mass spectrometry. In chromatographic analysis, DB-5MS column was used as the stationary phase for separation under the column heating program. In mass spectrometric analysis, electron impact ion source was used for ionization, multiple reaction monitoring mode was used for detection, and internal standard method was used for quantification. As shown by the results, linear relationships between the ratios of the corresponding peak areas to the internal standard peak areas and the ratios of mass concentrations of 62 organic pollutants to their internal standards were kept in the range of 5.00‒250 μg·L⁻¹, the detection limits （3.143s） of the solid phase extraction method were in the range of 0.5‒2.8 ng·L⁻¹, and the detection limits （3.143s） of the liquid-liquid extraction method were in the range of 0.3‒3.5 ng·L⁻¹. Test for recovery was made by the standard addition method, giving results in the range of 58.3%−123% and RSDs （n=6） of the determined values were in the range of 1.1%‒25% for the liquid-liquid extraction method, and giving results in the range of 51.8%‒128% and RSDs （n=6） of the determined values were in the range of 1.4%‒21% for the solid phase extraction method.