Background. Organic tin compounds (OTCs), a group of high-risk hazardous substances, are highly concerned in safety regulation of consumer products especially for toys because they can cause serious damage to organs after prolonged or repeated exposure. Gastric juice migration is nowadays widely implemented to assess organic tin intake from toys or food-contact materials; however, the followed up detection method using sodium tetraethylborate [NaB(Et₄)] as a derivatization agent may directly lead to false positive of monomethyltins (MMT). Objective. In order to avoid the phenomena of false positive of MMT in the course of laboratory testing of toys, it is necessary and important to perform relative experimental and theoretical studies to reveal the cause of false positive of MMT. Method. With metal tin powder as a representative of inorganic tin which existed in real samples, it was treated with artificial gastric juice (0.07 mol/L·HCl), followed by ethyl derivatization using sodium tetraethylborate [NaB(Et)₄] and then analyzed by gas chromatography-mass spectrometry (GC-MS) according to the procedure specified in the standard of EN 71-3:2013+A3:2018 issued by the European Committee for Standardization (CEN). Results. Without any OTCs in the starting materials, MMT false positive can be reproduced by detecting 0.56 mg/L of triethylmethyltin (TEMT) together with approximately 1000 mg/L of tetraethyltin (TeET), which is similar to real samples. Further, it is demonstrated that the detected amount of TEMT is linearly related with the added amount of NaB(Et)₄, and that the formation of TEMT (methyl derivative) is easier than TeET (ethyl derivative) even though the ethyl group is present in a larger amount than the methyl group. Conclusions. The phenomena of MMT false positive which occurred in the laboratory testing of toys is mainly because that TEMT is highly likely to be obtained from the reaction of inorganic tin and trace level of methylation agent impurities contained in the derivatization reagent—NaB(Et)₄. To avoid MMT false positive, it is concluded that the maximum acceptable mole ratio of methylation agent impurities contained in NaB(Et)₄ is approximately 0.028%. This research is helpful to be aware of methylation impurities and is favorable to avoid false judgment caused by MMT false positive in routine analysis of toys.

中文翻译：

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基于胃液迁移的玩具中单甲基锡检测假阳性的实验与理论研究

背景。有机锡化合物（OTCs）是一类高危有害物质，由于长时间或反复接触会对人体器官造成严重损害，因此在消费品尤其是玩具的安全监管中受到高度关注。如今，胃液迁移被广泛用于评估玩具或食品接触材料中的有机锡摄入量；然而，后续使用四乙基硼酸钠[NaB(Et ₄ )]作为衍生剂的检测方法可能会直接导致单甲基锡（MMT）的假阳性。客观的. 为了避免玩具实验室检测过程中出现MMT假阳性现象，进行相关的实验和理论研究以揭示MMT假阳性的原因是必要且重要的。方法。以金属锡粉作为实际样品中存在的无机锡的代表，用人工胃液（0.07 mol/L·HCl）处理，然后用四乙基硼酸钠[NaB(Et) ₄ ]进行乙基衍生化，然后用根据欧洲标准化委员会 (CEN) 颁布的 EN 71-3:2013+A3:2018 标准中规定的程序进行气相色谱-质谱 (GC-MS)。结果. 如果起始材料中没有任何 OTC，则可以通过检测 0.56 mg/L 三乙基甲基锡 (TEMT) 和大约 1000 mg/L 四乙基锡 (TeET) 来重现 MMT 假阳性，这与真实样品相似。此外，证明了TEMT的检测量与NaB(Et) ₄的添加量呈线性相关，即使存在乙基，TEMT(甲基衍生物)的形成也比TeET(乙基衍生物)容易。量大于甲基。结论. 玩具实验室检测中出现MMT假阳性的现象，主要是因为TEMT极有可能是由无机锡与衍生化试剂——NaB(Et) ₄中含有的微量甲基化剂杂质反应得到的。为避免 MMT 假阳性，得出的结论是 NaB(Et) ₄中所含甲基化剂杂质的最大可接受摩尔比约为 0.028%。本研究有助于了解甲基化杂质，有利于避免玩具常规分析中MMT假阳性造成的误判。