李登昆, 陈春静, 刘祥萍, 张云, 倪海平, 李磊. 串联固相萃取-气相色谱串联质谱法同时测定生活饮用水中10种N-亚硝胺[J]. 环境与职业医学, 2022, 39(8): 924-930, 936. DOI: 10.11836/JEOM21505
引用本文: 李登昆, 陈春静, 刘祥萍, 张云, 倪海平, 李磊. 串联固相萃取-气相色谱串联质谱法同时测定生活饮用水中10种N-亚硝胺[J]. 环境与职业医学, 2022, 39(8): 924-930, 936. DOI: 10.11836/JEOM21505
LI Dengkun, CHEN Chunjing, LIU Xiangping, ZHANG Yun, NI Haiping, LI Lei. Simultaneous determination of 10 N-nitrosamines in drinking water by tandem solid phase extraction-gas chromatography tandem mass spectrometry[J]. Journal of Environmental and Occupational Medicine, 2022, 39(8): 924-930, 936. DOI: 10.11836/JEOM21505
Citation: LI Dengkun, CHEN Chunjing, LIU Xiangping, ZHANG Yun, NI Haiping, LI Lei. Simultaneous determination of 10 N-nitrosamines in drinking water by tandem solid phase extraction-gas chromatography tandem mass spectrometry[J]. Journal of Environmental and Occupational Medicine, 2022, 39(8): 924-930, 936. DOI: 10.11836/JEOM21505

串联固相萃取-气相色谱串联质谱法同时测定生活饮用水中10种N-亚硝胺

Simultaneous determination of 10 N-nitrosamines in drinking water by tandem solid phase extraction-gas chromatography tandem mass spectrometry

  • 摘要: 背景

    饮用水消毒副产物N-亚硝胺对哺乳动物具有强烈的致癌性。饮用水中N-亚硝胺的污染状况在ng·L−1水平,准确定性、定量分析存在较大困难,因此开发一种灵敏、准确的生活饮用水中N-亚硝胺的分析方法十分必要。

    目的

    建立生活饮用水中10种N-亚硝胺同时测定的串联固相萃取-气相色谱串联质谱法。应用建立的方法测定南京市生活饮用水中10种N-亚硝胺的含量,初步了解南京市生活饮用水中N-亚硝胺的污染状况。

    方法

    预实验对比椰壳活性炭、HLB Pro两种固相萃取小柱对10种N-亚硝胺的萃取效率。采用固相萃取小柱连接件将椰壳活性炭与HLB Pro固相萃取小柱进行串联,分别组合成椰壳活性炭(上)-HLB Pro(下)与HLB Pro(上)-椰壳活性炭(下)两种串联方式萃取加标样品,结合直接、独立两种洗脱方式优化最佳萃取效率。2021年11—12月用1 L棕色玻璃采样瓶采集南京地区9家市政供水单位的原水9份、出厂水10份及末梢水7份,1.0 L生活饮用水样品加入同位素内标制备成含25 ng·L−1同位素内标的待测样品。全自动固相萃取仪以15 mL·min−1的速率全部上样至HLB Pro(上)-椰壳活性炭(下)串联固相萃取小柱。萃取完成后将串联固相萃取小柱转移至固相萃取真空装置,HLB Pro、椰壳活性炭固相萃取小柱分别用10 mL二氯甲烷洗脱,合并二氯甲烷洗脱液并移除上层少量水相,氮吹浓缩至1.0 mL左右,气相色谱质谱仪检测、同位素内标法定量。

    结果

    预实验发现椰壳活性炭、HLB Pro两种固相萃取小柱对生活饮用水中 10 种N-亚硝胺的萃取效率具有较高的互补性。采用HLB Pro(上)-椰壳活性炭(下)串联固相萃取方式、独立洗脱、洗脱液合并浓缩的程序,可以获取最佳萃取效率。在此条件下,采用气相色谱串联质谱法检测,10种N-亚硝胺组分在2~50 ng·L−1的范围内线性关系良好,相关系数均大于0.9996,方法检出限为0.149~0.211 ng·L−1,测定下限为0.596~0.844 ng·L−1。在5.0、15、30 ng·L−1加标浓度下,10种N-亚硝胺平均加标回收率88.0%~104.8%,相对标准偏差1.22%~4.87%。应用本法对南京市生活饮用水中10种N-亚硝胺含量进行测定,检测结果显示10种N-亚硝胺在原水、出厂水和末梢水中均有不同程度的检出,各组分检出率0%~100%,检出质量浓度ND~27.6 ng·L−1

    结论

    本研究建立的串联固相萃取-气相色谱串联质谱法能够实现生活饮用水中多种N-亚硝胺高灵敏、高通量的同时测定。

     

    Abstract: Background

    N-nitrosamines, a group of by-products of drinking water disinfection, have strong cytotoxicity to mammals. N-nitrosamines in drinking water are at the ng·L−1 level, and its accurate qualitative and quantitative analysis is difficult, so it is necessary to develop a sensitive and accurate method to determine N-nitrosamines in drinking water.

    Objective

    To establish a solid phase extraction-gas chromatography tandem mass spectrometry (GC-MS/MS) method for simultaneous determination of 10 kinds of N-nitrosamines in drinking water. To apply the established method to determine the levels of 10 kinds of N-nitrosamines in drinking water in Nanjing, and to understand the pollution status.

    Methods

    Coconut charcoal solid phase extraction (SPE) cartridge and HLB Pro SPE cartridge were compared for the extraction efficiency of 10 N-nitrosamines in drinking water. A coconut charcoal SPE cartridge and a HLB Pro SPE cartridge were concatenated using a SPE connector, and then formed two combinations: coconut charcoal (top)-HLB Pro (bottom) and HLB Pro (top)-coconut charcoal (bottom), to extract the spiked samples, and combined with direct and independent elution ways to obtain the best extraction efficiency. From November to December 2021, 9 raw water, 10 finished water, and 7 tap water samples were collected from 9 municipal water supply units in Nanjing with 1 L brown glass sampling bottles. An 1.0 L drinking water sample was added with the isotope internal standard to prepare a test sample containing an isotope internal standard concentration of 25 ng·L−1. The automatic SPE instrument loaded all the 1.0 L drinking water samples to the tandem SPE cartridge of the HLB Pro (top)-coconut charcoal (bottom) at the rate of 15 mL·min−1. After extraction, the HLB Pro SPE cartridge and coconut charcoal SPE cartridge were transferred to the solid phase extraction vacuum device and eluted with 10 mL of dichloromethane respectively, then the dichloromethane eluents were combined, and concentrated to about 1.0 mL by nitrogen blowing after a small amount of the upper aqueous phase was removed. The concentrated solution was detected by GC-MS/MS and quantified by isotope internal standard method.

    Results

    The comparison of sample spike recovery experiments showed that coconut charcoal solid phase extraction (SPE) cartridge and HLB Pro SPE cartridge presented highcomplementarity for the extraction efficiency of 10 N-nitrosamines in drinking water. Using HLB Pro (top)-coconut charcoal (bottom), independent elution, and combined with eluents, the optimal extraction efficiency was obtained. Under these conditions, by GC MS/MS, the 10 N-nitrosamines showed a good linear relationship within the range of 2–50 ng·L−1, the correlation coefficients were all greater than 0.9996, the method detection limit was 0.149–0.211 ng·L−1, and the limit of quantification was 0.596–0.844 ng·L−1. At the spiked concentrations of 5.0, 15, and 30 ng·L−1, the average recoveries of the 10 kinds of N-nitrosamines were 88.0%–104.8%, and the relative standard deviations were 1.22%–4.87%. When applying the method to determine the concentrations of the 10 N-nitrosamines in Nanjing drinking water, the results showed that the 10 N-nitrosamines were positive in different degrees in raw water, finish water, and terminal water, the detection rates were 0%–100%, and the concentrations were ND–27.6 ng·L−1.

    Conclusion

    This tandem solid phase extraction-gas chromatography tandem mass spectrometry method can achieve simultaneous determination of a variety of N-nitrosamines in drinking water with high sensitivity and high throughput.

     

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