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Title: [The transformation of microcystin-LR during tap water treatment process and analysis of its degradation products].
Author: Ding XL, Zhu PF, Huang CH, Zhang Q, Zhu JY, Liu WW, Zhou WJ.
Journal: Zhonghua Yu Fang Yi Xue Za Zhi; 2018 Sep 06; 52(9):898-903. PubMed ID: 30196635.
Abstract:
Objective: To establish a liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for the determination of microcystin-LR (MC-LR) in drinking water, investigate its removal efficiency during tap water advanced treatment process and analyze its degradation products in the tap water. Methods: Two parallel water samples were collected from each point of tap water advanced treatment process in September 2015, November 2015 and January 2016, respectively, and treated by mixing, filtration, concentration, elution, nitrogen blow and re-dissolvement. The samples were analyzed by LC/MS/MS to determine the MC-LR concentration and its removal efficiency during treatment process. The combination of actual water enrichment (including source water enrichment of 50 times and 1 500 times concentrated, finished water enrichment of 50 times and 2 500 times concentrated) and laboratory simulated water (including the mixture of MC-LR and liquid chlorine in the mass ratio of 1∶10, 1∶20, 1∶100 and 1∶1 000, respectively) were used to qualitative analyze the MC-LR degradation products by Orbitrap mass spectrometry. Results: The linearity of MC-LR ranged from 2 to 200 μg/L with the detection limit of 0.007 9 μg/L and the limit of quantification of 0.026 3 μg/L. The recovery rate of MC-LR from different contration in drinking water were from 94.88%-101.47%. The intra-day precision was 2.51%-7.93% and the intra-day precision was 3.24%-8.41%. The average concentration of MC-LR in source water was (0.631±0.262) μg/L, 94.0% of which can be removed by ozone exposure while the concentrate was (0.038±0.016) μg/L, biological pre-treatment and chlorination. The remaining can hardly be removed by sand filtration, ozone exposure, activated carbon, ultrafiltration and other processes. The MC-LR average concentration in the finished water maintained at about (0.036±0.016) μg/L. Degradation products including hydroxy-microcystin, methyl-hydroxy-microcystin, methyl-microcystin were identified in the laboratory simulated water of the mixture of MC-LR and liquid chlorine in the mass ratio of 1∶10. Conclusion: The established MC-LR detection method can be well applied to the monitoring of MC-LR in drinking water due to its simple pre-treatment process and good methodological validation parameters. The degradation products of treatment processes was different. 目的：基于液相色谱质谱联用（LC/MS/MS）技术建立饮用水中微囊藻毒素-LR (MC-LR）的定量检测方法，分析自来水深度处理工艺对MC-LR的去除效果，探讨出厂水中可能含有的MC-LR降解产物情况。 方法： 2015年9、11月和2016年1月分别采集自来水处理工艺各步骤平行水样2份，经混匀、过滤、富集、洗脱、氮吹、复溶等处理后，采用建立的LC/MS/MS检测方法对各样品进行MC-LR检测并分析处理流程对MC-LR的去除效果。利用实际采集水样富集与实验室模拟水样相结合的方式，采用Orbitrap组合型质谱对50倍和1 500倍浓缩的水源水富集物，50倍和2 500倍浓缩的出厂水富集物，以及质量比为1∶10、1∶20、1∶100、1∶1 000的MC-LR标准品与液氯混合的模拟水样进行MC-LR降解产物的定性分析。 结果： MC-LR在2~200 μg/L范围内线性关系良好，方法检出限为0.007 9 μg/L、定量限为0.026 3 μg/L；饮用水加标回收率94.88%~101.47%；日内精密度为2.51%~7.93%；日间精密度为3.24%~8.41%。水源水MC-LR的浓度为（0.631±0.262）μg/L，经臭氧接触池、生物预处理和加氯处理后，94.0%的MC-LR能够被去除，MC-LR浓度为（00.038±0.016）μg/L，后续工艺几乎无法去除残留的MC-LR，出厂水MC-LR浓度为（0.036±0.016）μg/L。在模拟水样中发现4种可能的降解产物，分别为羟基-微囊藻毒素、甲基-羟基-微囊藻毒素和甲基-微囊藻毒素。 结论：建立的MC-LR检测方法样品前处理过程简单，能很好地应用于日常饮用水MC-LR的监测，水样分析得到4种不同的MC-LR降解产物。.

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