胃液迁移模型的有机锡检测中假阳性现象

有机锡作为一类高风险的有害物质,是各类消费品检测中重点关注的物质之一。 在日常检测中发现,当采用胃液迁移模型对以锡或镀锡为基材的涂层材料进行有机锡检测时,经常会出现甲基锡的假阳性现象。 本文采用金属锡粉模拟实际样品中的无机锡成分,通过GC-MS检测发现单质锡可转化为三乙基甲基锡,其质量浓度为0.56 mg/L,并由此提出了其来源的3种可能性,即1)三乙基甲基锡由无机锡与衍生试剂中微量甲基化试剂反应得到;2)三乙基甲基锡由四乙基锡在进样口或色谱柱内分解得到;3)三乙基甲基锡由四乙基锡于色谱柱内发生甲基取代反应得到或来自于进样口残留污染。 通过实验对假设进行验证。 结果表明,假阳性现象主要是由衍生试剂四乙基硼酸钠中含有的极少量甲基化试剂引起。 因此,相关标准应对衍生试剂中甲基化试剂的含量做出规定,以避免引起误判。

Research of False Positive Phenomenon in Organotin Determination Based on Gastric Juice Migration Model

Organotin, a group of high risk hazardous substances, is highly concerned in consuming products testing. False positive of methyltin species is frequently found in routine analysis of migratable organotin compounds in surface coatings of tins or tin plated materials. It was found by GC-MS that 0.56 mg/L triethylmethyltin(TEMT) had been converted from elemental tin by using metal tin powder to simulate inorganic tin content present in actual samples. Three possible assumptions concerning the source of triethylmethyltin were then proposed:1)TEMT derived from reaction of inorganic tin with trace methylating agent contained in derivatization reagent. 2)TEMT derived from decomposition of tetraethyltin(TrET) at sample inlet or inside the column. 3)TEMT derived from methyl-substitution reaction of TrET or residual contamination of sample inlet . Relevant confirmation experiments were then carried out accordingly. It was finally found that triethylmethyltin had been generated from very little amount of methylating agents present in the derivatization reagent-sodium tetraethylborate. Therefore, the content of non-ethyl alkylation agent contained in the derivatization reagent should be specified in related standards to avoid arousing erroneous judgment.