Rapid Analysis of Phthalate Esters in Plastic Toys by Laser Raman Technology
XU Xin-xia1, SHEN Xue-jing1,2*, YANG Xiao-bing3, CHEN Ji-wen4, ZHAO Meng-di3, LIU Jia1, ZHAO Ying1, CUI Fei-peng2, LI Xiao-peng2
1. Central Iron and Steel Research Institute, Beijing 100081, China
2. NCS Testing Technology Co., Ltd., Beijing 100094, China
3. Beijing Customs Testing Center, Beijing 100094, China
4. North China University of Technology, Beijing 100144, China
Abstract：Many plastics can be used to make toys, such as polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), etc. A certain amount of plasticizer will be added to the plastics in production, in order to make the toys have better ductility and formability. It is generally known that the phthalate esters (PAEs) are widely used plasticizers in toy plastics. The common PAEs are diethylhexylphthalate (DEHP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP). Research suggests that the molecular structure of the PAEs is similar to estrogen, so the PAEs is also called “environmental hormone”. The PAEs can cause endocrine disorders, affect male reproductive ability, promote premature female puberty, and endanger children’s reproductive system in long-term or high concentration environments. Beijing Customs pointed out that the proportion of excessive PAEs was the largest in the unqualified toys. Therefore, sampling inspection is needed to ensure safety in the import and export of toys. The current standard test method of PAEs in toy plastics in China’s Customs has some shortcomings, such as complex pre-treatment process, expensive testing equipment and high professional requirements for operators, which is not conducive to the rapid detection of the PAEs and seriously restricts the rapid customs clearance of toys. Therefore, it is urgent to develop a rapid and accurate method to detect the PAEs content in toy plastics. The purpose of this paper is to establish a rapid screening technology for the PAEs in toy plastics. Firstly, the molecular configurations of DEHP, DBP and BBP were optimized, and the molecular vibration spectra were calculated by density functional theory (DFT). On this basis, the Raman spectra of DEHP, DBP and BBP measured by laser Raman technology were identified and the molecular vibration modes were assigned. This result is reliable and consistent with the actual spectral data. It shows that this method can correctly assign the characteristic peaks of Raman spectra of PAEs molecule and can be used for qualitative analysis of DEHP, DBP and BBP. Secondly, we studied the method of rapid and direct quantitative determination of the PAEs in plastics by Raman spectrometer. The results showed that the content of the DEHP, DBP and BBP were linearly correlated with the intensity of its characteristic peak, and the correlation coefficient was 0.98, 0.99 and 0.99, respectively, which indicated that the method had a high accuracy in quantitative analysis of the PAEs. Finally, the laser Raman spectrometer was used for the first time to test toy samples on the market without any pretreatment. The Raman spectra of children’s toys were obtained by optimizing the background subtraction method in the collection process. The type of the PAEs was identified as the DEHP by characteristic peaks, and the content of the DEHP was calculated. Meanwhile, the type and content of the PAEs in toy plastics were further detected by GC-MS. The consistency of the two methods was satisfactory. In conclusion, the rapid detection of the types and contents of the PAEs in plastic toys by laser Raman technology can shorten the detection time of plasticizers in children’s toys without damaging toys, and save testing costs. This method can also be applied to the qualitative and quantitative analysis of the PAEs plasticizer in other solid samples, and it is expected to be applied to the customs site to improve customs clearance speed.
Key words：Laser Raman; Phthalate esters; Density functional theory (DFT); Quantitative analysis
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