Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8 µg L^–1) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1 µg L^–1. Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown.

Graphical Abstract

中文翻译：

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椰油酰胺丙基甜菜碱——泳池水中含氮消毒副产物的潜在来源

大多数公共泳池的水处理涉及使用活性氯进行消毒，从而导致消毒副产物 (DBP) 的形成。其中，含氮化合物（N-DBPs）毒性增加，对人体健康产生不利影响，是最受关注的。作为各种游泳沐浴露的主要成分，椰油酰胺丙基甜菜碱 (CAPB) 是泳池水中潜在的、但仍被低估的 N-DBP 人为前体。本研究的目的是研究水氯化条件下CAPB的转化途径和机制。使用高效液相色谱和二维气相色谱与高分辨率质谱联用来搜索和初步鉴定 CAPB 转化产物的初级和最终产物。首次在模型氯化实验中揭示了多种 DBP，最多含有 5 个氯原子，其中包括与羟基和附加羰基组合的 DBP。所提出的形成机制涉及第一阶段仲酰胺氢原子的亲核取代，以及随后的自由基和亲电加成反应，导致在烷基链中非选择性引入卤素原子和羟基。深度转化产物包括短链氯化烃及其氧化产物以及具有高毒性和致癌性的二甲基氨基甲酰氯。对真实游泳池水样的针对性分析证实了模型实验的结果，能够半定量测定 CAPB (0.8 µg L ^–1 ) 和 18 种初级 DBP，其中包括 10 种总浓度为 0.1 µg L ^–1的含氯化合物。其中，一氯（50%）和羟基二氯（25%）衍生物占主导地位。使用 QSAR/QSTR 方法评估了主要 DBP 的毒性和健康。因此，表明了与洗涤剂和化妆品的广泛使用相关的新一类具有潜在毒性的含氯 DBP 的形成的可能性。

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