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

Experimental and Theoretical Study on the False Positive of Monomethyltin Determination in Toys Based on Gastric Juice Migration

“…Reproduction of MMT False Positive. Using tin or tin plating which contained OTCs-free real toy samples, our preliminary study [15] has already demonstrated that 0.44∼0.93 mg/kg MMT could be detected after treating these samples according to the procedures specified in EN 71-3+A3:2018 [7]. Here, in order to provide a better understanding, tin powder was used to simulate tin or tin-plated materials contained in toy samples and was treated by the same procedure described in Section 2.4, and the obtained n-hexane extract was then analyzed by GC-MS. Figure 1 e mass spectrum was matched by NIST MS Search 2.2 database, giving a very high probability of 0.97 to be TEMT, and the concentration of TEMT was calculated to be 0.56 mg/L by external calibration, thus indicating elemental tin alone can be converted into TEMT.…”

“…It is worth noting that EN 71-3 is the first standard to adopt the gastric juice migration model to simulate the contact condition between toys and gastric juice after children had swallowed toys, wherein gastric juice is simulated by the hydrochloric acid solution to extract soluble elements including OTCs released from toys [7]. However, our previous study clearly demonstrated [15] that when analyzing surface coating materials or clear varnish on tin or tin-plated substrates according to the standard of EN 71-3, there would always be positive findings of monomethyltin (MMT), which were determined as triethylmethyltin (TEMT) in GC-MS and were typically below 10 mg/kg. To the best of our knowledge, OTCs are barely added into the coatings at such low level which is not sufficient for being functional.…”