The fish embryo toxicity (FET) test with the zebrafish Danio rerio is widely used to assess the acute toxicity of chemicals thereby serving as animal alternative to the acute fish toxicity test. The minimal toxicity of neutral chemicals in the FET can be predicted with a previously published Quantitative Structure-Activity Relationship (QSAR) based on the liposome-water partition coefficient K_lipw. Such a QSAR may serve to plan toxicity testing and to evaluate whether an observed effect is caused by a specific mode of action (MoA). The applicability domain of this QSAR was extended to ionizable organic chemicals (IOC) without any modification of slope and intercept simply by replacing the K_lipw with the speciation-corrected liposome-water distribution ratio (D_lipw(pH)) as descriptor for the uptake into the embryo. FET LC₅₀ values of IOCs were extracted from an existing FET database and published literature. IOCs were selected that are present concomitantly as neutral and charged, species, i.e., acids with an acidity constant pK_a <10 and bases with pK_a>5. IOCs were grouped according to their putative MoA of acute aquatic toxicity. The toxic ratios (TR) in the FET were derived by of the experimental FET-LC₅₀ in comparison with the baseline toxicity QSAR. Baseline toxicants were confirmed to align well with the FET baseline toxicity QSAR (TR < 10). Chemicals identified to act as specific or reactive chemicals with the toxic ratio analysis in the FET test (TR > 10) were generally consistent with MoA classification for acute fish toxicity with a few exceptions that were suspected to have had issues with the stability of the pH during testing. One critical aspect for the effect analysis of ionizable chemicals is the pH, since the difference between pH and pK_a determines the speciation and thereby the D_lipw(pH).

斑马鱼Danio rerio的鱼胚毒性（FET）测试被广泛用于评估化学药品的急性毒性，从而成为急性鱼毒性测试的动物替代品。FET中的中性化学品的最小毒性可以通过基于脂质体-水分配系数K _lipw的先前发表的定量结构-活性关系（QSAR）进行_预测。这样的QSAR可以用来计划毒性测试和评估观察到的效果是否是由特定的作用方式（MoA）引起的。只需替换K _lipw，即可将QSAR的适用范围扩展到可电离的有机化学物质（IOC），而无需对斜率和截距进行任何修改用形态校正的脂质体-水分配比（D _lipw（pH））作为对胚胎摄取的描述子。从现有的FET数据库和公开的文献中提取IOLC的FET LC ₅₀值。选择了以中性和带电状态同时存在的IOC，即酸度常数p K _a <10的酸和p K _a > 5的碱。根据对急性水生毒性的推定MoA将IOC分组。FET中的毒性比（TR）由实验性FET-LC ₅₀得出与基线毒性QSAR相比。确认基线毒物与FET基线毒性QSAR吻合良好（TR <10）。经FET测试的毒性比分析（TR> 10）被鉴定为是特定化学或反应性化学物质的化学物质，与MoA的急性鱼类毒性分类基本一致，但有少数例外被怀疑与pH值的稳定性有关。在测试期间。pH值是可电离化学物质效果分析的一个关键方面，因为pH值与p K _a之差决定了物种，进而决定了D _lipw（pH）。