Research On Detection Method And False Positive Phenomenon Of Organotin In Toys Based On EU Standards

China is a major producer of toys and baby products.However,a considerable number of toys and baby products were recalled every year because the content of harmful substances wasn't in conformity with the relevant laws and regulations of each exporting country.Organotin compound(OTC)is one of the harmful substances.The EU standard is currently the most widely used standard for testing OTCs in toys.In EN 71-3:2019 released in 2019,the content of 11 kinds of OTCs were restricted.With the improvement of people's safety awareness,not only the toy industry but also other industries have imposed more restrictions on the types of OTCs.Compared with the old version released in 2015 by the International Environmental Protection Textile Association,the Oeko-Tex standard 100 issued in 2016increased its limit to the types of OTCs from 4 to 14,of which 4 types of OTCs were not limited by the EU toy standard.It can be seen that the 11 types of OTCs defined in the latest EU standard EN 71-3:2019 have gradually failed to meet people's needs.Meanwhile,domestic testing laboratories still use the dated European standard EN 71-3:2013/A2:2017which has been difficult to achieve the OTCs testing requirements for the second category of toy materials.Therefore new testing methods must be sought to solve the problem of testing limits for the second category of toy materials.In addition,when routine tests for tin or tin-plated coating materials(no organotin contained)in accordance with the gastric juice migration procedure in the EU Toy Safety Standard EN 71-3:2019,monomethyltin was often detected,which didn't in accordance with the fact that the raw material didn't contain organotin,leading to a false positive of monomethyltin.In this thesis,based on theof all types of organotin defined in various industries,a method for detecting 20kinds of migratory organotin in toy materials based on GC-MS/MS has been established for the first time,which can be combined with different pretreatment ways to serve in other fields.Moreover,by employing GC-MS,the false positive phenomenon of monomethyltin in toy coating materials has been detected and confirmed.The main content of the thesis is as follows:(1)Determination of 20 migratable organotins in toys based on GC-MS/MS methodAfter migration from simulated gastric juice(HCl)followed by derivatization using the derivatizing agent(sodium tetraethylborate),the OTCs were analyzed by selective ion monitoring mode(MRM),during which,migration conditions,derivatization steps as well as operating parameters of GC-MS/MS have been optimized.From the experimental result,all of the 20 kinds of OTCs displayed good linear relationship in the concentration range from0.005 to 0.200 mg/L with the linear correlation coefficients(R~2)of 0.9963?0.9999,their detection limits were as low as 0.019?3.196?g/kg with the limit of quantifications between0.065 and 10.652?g/kg,and the recoveries of OTCs in samples were in the range of 80.6%?117.2%with relative standard deviations(RSD)less than 5%(n=6).Compared with GC-MS,the most commonly employed method for OCTs detection in toys,the newly established method can separate 20 different kinds of OTCs within 20 min at one time,indicating the advantages of strong selectivity,accurate quantification,high sensitivity with a very low detection limits and quantitation limits,dissolving the problem that the quantitation limit of OTCs for the second type of toy materials was difficult to be achieved.Furthermore,this method also extends the detection limitation of OTCs types in toys to 20 types from the original 11 types given in the EU standard.The developed method is proved to be comprehensive,efficient,reliable and sensitive for fast determination of OTCs in toys.The work is detailed in Chapter 2 of this article.(2)Detection and confirmation of monomethyltin false positive from toys by GC-MSAfter migration from simulated gastric juice(HCl)followed by derivatization using the derivatizing agent(sodium tetraethylborate),the monomethyltin was analyzed by selective ion monitoring mode(MRM),during which,migration conditions,derivatization steps as well as operating parameters of GC-MS have been optimized.From the experimental result,the monomethyltin displayed good linear relationship in the concentration range from 0.02 to 1.0mg/L with the linear correlation coefficients(R~2)of 0.992,the detection limit was 0.11 mg/kg with the limit of quantification of 0.32 mg/kg,and the recoveries of monomethyltin in samples were in the range of 86.2%?104.2%with relative standard deviations(RSD)of 3.1%?8.2%(n=6).In daily testing,it was found that when tin or tin-plated coating materials were tested for organotin according to the gastric juice migration model described in the European Union EN 71-3:2019 standard,false positive phenomena of monomethyltin often occur,and studies have confirmed that this phenomenon was caused by the two key links of simulated gastric fluid and derivative reagents.Therefore,it was confirmed from these two aspects:1.replacement of simulated gastric fluid with methanol and acetone;2.replacement of sodium tetraethylborate with sodium tetrapropylborate.The results showed that after replacing the simulated gastric fluid with methanol and acetone,no corresponding monomethyltin derivative products were detected.However,after replacing sodium tetraethyl borate with sodium tetrapropylborate,the corresponding monomethyltin derivative products were still detected.Thus,the former can be used to confirm the false positive phenomenon of organotin in the gastric fluid migration model.In addition,when monomethyltin was detected,the tin content in the filtrate can be compared with the tin content detected in the n-hexane layer as an auxiliary criterion for false positive of methyl tin.The work is detailed in Chapter 3 of this article.The above research has provided an effective solution to the problem that available domestic testing methods can hardly reach the quantitative limit of organotin in toy materials in the EU standards,and figured out a broad,efficient,sensitive and reliable organotin detection method for toy manufacturers and professional testing labs.What's more,a simple,efficient and reliable experimental method was established to judge the false positive phenomenon of monomethyltin in the coating samples,which ensured the reliability of the experimental results.The research results of this thesis will promote the development of toy trade between China and the world.