Pentachlorophenol (PCP) is a widespread and persistent hydrophobic organic pollutant in the environment despite its restricted public use. Risk assessment of such hydrophobic organic compounds (HOCs) is challenging because sorption and volatilization issues during toxicity test often lead to inconsistent exposure concentration. Considering the hydrophobicity of the PCP, in this study, a passive dosing format was applied by adopting a silicone O-ring as a reservoir and evaluated its applicability on the determination of PCP on Daphnia magna. Results obtained with passive dosing method were compared with that of solvent spiking method. We hypothesized that the passive dosing method may provide more reliable and accurate toxicity results than conventional solvent spiking approach. As a result, the partition coefficient of PCP between methanol and a test medium (log KMeOH:ISO) was 2.1, which enabled the maintenance of reliable exposure concentration throughout the experiment. In the acute toxicity tests, passive dosing and solvent spiking showed similar EC50 values of 576 and 485 µg/L for 24 h, and 362 and 374 µg/L for 48 h, respectively, which overlap with EC50 values of previous studies. Altogether, both methods were suitable for the acute toxicity assessment of hydrophobic PCP.

中文翻译：

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比较被动加药和溶剂加料方法以确定五氯苯酚对大型蚤的急性毒性作用。

五氯苯酚（PCP）尽管限制了公共用途，但在环境中却是一种广泛且持久的疏水性有机污染物。此类疏水性有机化合物（HOC）的风险评估具有挑战性，因为毒性测试期间的吸附和挥发问题通常会导致不一致的暴露浓度。考虑到五氯苯酚的疏水性，在这项研究中，采用有机硅O形环作为储液罐，采用了被动剂量形式，并评估了其在测定大型蚤中五氯苯酚中的适用性。将被动加料方法与溶剂加料方法获得的结果进行比较。我们假设被动加药方法可能比常规溶剂加标方法提供更可靠和准确的毒性结果。结果是，PCP在甲醇和测试介质（对数KMeOH：ISO）之间的分配系数为2.1，从而在整个实验过程中都能保持可靠的暴露浓度。在急性毒性试验中，被动给药和溶剂加标显示24小时的EC50值分别为576和485 µg / L，48小时的362和374 µg / L，与先前研究的EC50值重叠。总之，这两种方法均适用于疏水性五氯苯酚的急性毒性评估。