生活饮用水中三卤甲烷的测定及其致癌风险评估

Determination and Carcinogenic Risk Assessment of Trihalomethanes in Drinking Water

采用顶空-固相微萃取结合气相色谱-质谱法测定饮用水中4种三卤甲烷(CHCl3、CHBrCl2、CHBr2Cl、CHBr3)。将25mL水样加入40mL顶空瓶,用0.2mol·L^(-1)盐酸溶液调节pH=8.0,加入20.0mg·L^(-1) 1,2-二溴丙烷(内标)溶液0.20mL,加入7.0g氯化钠,用固相微萃取装置在30℃萃取30min后,在250℃解析50s后进行气相色谱-质谱法测定。采用TG-5MS色谱柱(30m×0.25mm,0.25μm)进行分离,质谱中选择电子轰击离子源和选择离子监测模式。4种三卤甲烷的线性范围均为10～160μg·L^(-1),检出限(3S/N)在0.16～0.26μg·L^(-1)之间。加标回收率为95.8%～120%,测定值的相对标准偏差(n=5)在1.4%～15%。采用此方法测得内蒙古5个城市15个饮用水样中4种三卤甲烷的质量浓度水平为8.31～81.14μg·L^(-1),其中CHBr2Cl为最主要致癌因子,5个城市的总致癌风险分别为5.12×10^(-5),3.82×10^(-5),5.84×10^(-5),5.53×10^(-5),6.25×10-6。

A method of headspace-solid phase microextraction combined with gas chromatography-mass sepctrometry was applied to determination of 4 kinds of trihalomethanes(CHCl3,CHBrCl2,CHBr2Cl,CHBr3)in drinking water.The water sample(25 mL)was added into a 40 mL headspace vial and adjusted to pH 8.0 with 0.2 mol·L^-1 HCl solution.Then 0.20mL of 20.0mg·L^-1 1,2-dibromopropane solution as internal standard and 7.0 g of sodium chloride were added,and the mixture was extracted with a solid phase microextraction apparatus at 30℃ for 30 min and the analytes were determined by gas chromatography-mass spectrometry after being deposited at 250℃ for 50 s.A TG-5MS chromatographic column(30m×0.25mm,0.25μm)was used for separation. Electron bombardment ion source and selective ion monitoring mode were selected in mass spectrometry.The same linear range of the 4kinds of trihalomethanes was 10-160μg·L^-1,and the detection limits(3S/N)were in the range of 0.16-0.26μg·L^-1.Values of recovery obtained by standard addition method ranged from 95.8% to 120%,and the relative standard deviations(n=5)of the measured values ranged from 1.4% to 15%.The method was applied to determination of the 4 kinds of trihalomethanes in 15 drinking water samples from 5 cities in Inner Mongolia,giving mass concentration in the range of 8.31-81.14μg·L^-1.CHBr2Cl was the most important carcinogenic factor and the total cancer risks of the 5 cities were 5.12×10^-5,3.82×10^-5 ,5.84×10^-5,5.53×10^-5 and 6.25×10^-6,respectively.