Department of Environmental Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark.
Environ Toxicol Chem. 2011 Feb;30(2):354-9. doi: 10.1002/etc.391.
The uptake and accumulation of most electrolytes will change with pH because of the different speciation states of these compounds at various pH. Non-ionized compounds will partition into fatty and organic phases (such as cell membranes) more readily than the corresponding charged compounds, and therefore a higher toxicity can be expected. The current study examines the pH-dependent toxicity and bioaccumulation of the bivalent weak base chloroquine (pK(a): 10.47 and 6.33, log K(OW) 4.67) tested on Salix viminalis (basket willow) and Daphnia magna (water flea). The transpiration rates of hydroponically grown willow cuttings were used to determine the toxicity of chloroquine at pH levels of 6, 7, 8, and 9. Root concentration factors were calculated from solution measurements. Results showed more than 10-fold higher toxicity and four to seven times higher root concentration factor at pH 9 than at pH 6. The toxicity of chloroquine was tested on Daphnia magna using the standard Organisation for Economic Co-operation and Development acute toxicity test modified to accommodate testing at pH levels of 7, 8, and 9. Increasing toxicity was seen at higher pH. The results of the current study confirm that the toxicity of weak bases with intermediate pK(a) values is higher at high pH levels.
由于这些化合物在不同 pH 值下的不同形态，大多数电解质的摄取和积累都会随 pH 值而变化。非离子化合物比相应的带电化合物更容易分配到脂肪和有机相中（如细胞膜），因此可以预期更高的毒性。本研究考察了二价弱碱基氯喹（pK(a)：10.47 和 6.33，log K(OW) 4.67）在 pH 值为 6、7、8 和 9 时对柳树（柳树）和大型水蚤（水蚤）的毒性和生物累积的影响。水培生长的柳扦插的蒸腾速率用于确定氯喹在 pH 值为 6、7、8 和 9 时的毒性。根据溶液测量值计算根浓度系数。结果表明，在 pH 值为 9 时，毒性比 pH 值为 6 时高出 10 倍以上，根浓度系数高出 4 至 7 倍。采用经修改以适应 pH 值为 7、8 和 9 的测试的经济合作与发展组织（OECD）标准急性毒性试验对大型水蚤进行了氯喹的毒性测试。在较高的 pH 值下，观察到毒性增加。本研究的结果证实，具有中等 pK(a) 值的弱碱基的毒性在较高 pH 值下更高。
