[Determination of monomethyltin migration from toys by gas chromatography-mass spectrometry and confirmation of its false positive].

Based on migration procedures using simulated gastric juice specified in the EU toy Safety Standard EN 71-3:2013/A2:2017, a method was developed for the determination of monomethyltin (MMT) migration from toys by gas chromatography-mass spectrometry (GC-MS). Further, a reliable confirmation method for judgement of a false positive for MMT obtained by GC-MS, was established. After optimizing the migration conditions, derivatization steps and chromatographic parameters, the method yielded a linear range from 0.02 to 1.0 mg/L with a correlation coefficient (R2) of 0.9992. The limits of detection and quantification of the method were 0.11 and 0.32 mg/kg, respectively. The recoveries were 86.2%-104.2% under different spiked levels (0.5, 1.0 and 1.5 μg), and the relative standard deviations were 3.1%-8.2% (n=6). MMT migration ranging from 0.44 to 0.67 mg/kg was detected in the surface coating of tin-plating (Sn-Fe alloy) toy materials, which was subsequently confirmed to be false positive. Therefore, a novel confirmative approach using methanol or acetone as the migration solvent was proposed, aiming at verifying the false positive of MMT. The results showed that the previously positive MMT detected by GC-MS could no longer be detected when treated by these migration solvents.Hence, this approach can be used to confirm false positive detected for MMT after GC-MS detection.