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    固相萃取/液液萃取-气相色谱-串联质谱法测定生活饮用水中62种有机污染物的含量

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

    • 摘要: 取处理后的生活饮用水样品1 L置于全自动固相萃取仪中,固相萃取柱依次用5 mL二氯甲烷、5 mL乙酸乙酯淋洗,再依次用10 mL甲醇、10 mL水活化,以10 mL·min−1流量上样,用50 mL水洗涤并上样,抽干后用氮气干燥5 min,依次用5 mL甲醇、4 mL乙酸乙酯、4 mL体积比1∶1的乙酸乙酯-二氯甲烷的混合溶液、8 mL二氯甲烷洗脱,收集洗脱液。或者取处理后的生活饮用水样品1 L(pH为6~7),用30 mL二氯甲烷萃取5 min,收集有机相,重复萃取一次,水相用50%(体积分数)盐酸溶液调节pH不大于2,加入30 mL体积比1∶1的二氯甲烷-乙酸乙酯的混合溶液萃取,合并所有有机相,经无水硫酸钠脱水,加入5 mL体积比1∶1的乙酸乙酯-环己烷的混合溶液,于35 ℃氮吹浓缩至1.0 mL,通过Bio-Beads S-X3凝胶色谱柱净化,收集净化液。洗脱液或者净化液于35 ℃氮吹浓缩至近干,加入10 µL 10 mg·L−1混合同位素内标使用液,用二氯甲烷定容至1.0 mL,采用气相色谱-串联质谱法测定溶液中62种有机污染物的含量。在色谱分析中,以DB-5MS色谱柱为固定相,在柱升温程序下分离;在质谱分析中,以电子轰击离子源电离,多反应监测模式检测,内标法定量。结果显示,62种有机污染物的质量浓度均在5.00~250 μg·L−1内与其内标质量浓度的比值和对应峰面积与内标峰面积的比值呈线性关系,固相萃取法的检出限(3.143s)为0.5~2.8 ng·L−1,液液萃取法的检出限(3.143s)为0.3~3.5 ng·L−1。按照标准加入法进行回收试验,采用液液萃取法时,回收率为58.3%~123%,测定值的相对标准偏差(n=6)为1.1%~25%;采用固相萃取法时,回收率为51.8%~128%,测定值的相对标准偏差(n=6)为1.4%~21%。

       

      Abstract: 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.

       

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