Université Paris-Saclay, CEA, Service d'Étude du Comportement des Radionucléides, 91191, Gif-sur-Yvette, France.
Université Paris-Saclay, CEA, Service d'Étude du Comportement des Radionucléides, 91191, Gif-sur-Yvette, France.
Chemosphere. 2022 Oct;304:135155. doi: 10.1016/j.chemosphere.2022.135155. Epub 2022 May 31.
Liquid-liquid partition coefficient is a useful tool to predict biological and environmental fate of organic compounds, for example bioaccumulation or toxicity of lipophilic contaminants. Conversely, the partitioning of ionizable compounds is poorly studied in contrast to that of neutral compounds. Yet, such topic deserves attention, since numerous organic contaminants are ionizable as well as their degradation products. Hence, the contribution of charged species has to be considered in order to model accurately the mass balance or partition of ionizable compounds. In this context, we investigated the liquid-liquid partition of 13 ionizable compounds (oxalic acid, histidine, benzimidazole, etc.), covering various classes of compounds (carboxylic acids, amino-acids, etc.). The n-octanol/water partition coefficient was measured from pH 1 up to 13, in order to fully gather the distribution of both neutral and charged species. Empirical models describing these results are reviewed and partition parameters adjusted for charged species. The study of benzoic acid derivatives (benzoic, salicylic, ortho- and iso-phthalic acids) provides insights on the influence of chemical groups on the partitioning. In the case of tryptophan, the use of acid/base microconstants allowed to estimate the partition of both the zwitterion and its neutral tautomer. Despite a major zwitterionic form (log P(tryptophan) = -1.58 ± 0.30), the minor but neutral tautomer (log P(tryptophan) = +0.03 ± 0.30) drives the partition equilibrium. Overall, the provided data may be useful to assess the retention of contaminants, its dependency on pH and salinity variations, and thus understanding their environmental fate. Such data may also be useful as well for molecular simulation involving solvation of organic ions in aqueous and non-aqueous solvents.
分配系数是预测有机化合物生物和环境归宿（如亲脂性污染物的生物累积或毒性）的有用工具。相比之下，尽管可电离化合物的分配情况研究较少，但与中性化合物相比，这种情况值得关注。因为许多有机污染物及其降解产物都是可电离的。因此，为了准确模拟可电离化合物的质量平衡或分配，必须考虑带电物质的作用。在这种情况下，我们研究了 13 种可电离化合物（草酸、组氨酸、苯并咪唑等）的液-液分配，这些化合物涵盖了各种化合物类别（羧酸、氨基酸等）。从 pH 值 1 到 13 测量了正辛醇/水分配系数，以全面收集中性和带电物质的分布。本文综述了描述这些结果的经验模型，并对带电物质的分配参数进行了调整。对苯甲酸衍生物（苯甲酸、水杨酸、邻苯二甲酸和间苯二甲酸）的研究提供了有关化学基团对分配影响的见解。对于色氨酸，酸碱微常数的使用允许估算两性离子及其中性互变异构体的分配。尽管主要的两性离子形式（log P(tryptophan) = -1.58 ± 0.30），但次要但中性的互变异构体（log P(tryptophan) = +0.03 ± 0.30）驱动分配平衡。总体而言，提供的数据可用于评估污染物的保留情况、其对 pH 和盐度变化的依赖性，从而了解其环境归宿。这些数据也可能对涉及有机离子在水相和非水相溶剂中溶剂化的分子模拟有用。
