激光拉曼光谱快速筛查塑料玩具中邻苯二甲酸酯的研究

Rapid Analysis of Phthalate Esters in Plastic Toys by Laser Raman Technology

常见的玩具材料有聚氯乙烯(PVC)、聚丙烯(PP)、聚苯乙烯(PS)等。为了使玩具塑料有更好的延展性,有利于塑料成型,在加工过程中会加入一定量的塑化剂。邻苯二甲酸酯类(PAEs)塑化剂种类繁多,用途最为广泛,是玩具塑料中最普遍使用的塑化剂。常见的PAEs有邻苯二甲酸二(2-乙基己基)酯(DEHP)、邻苯二甲酸二丁酯(DBP)和邻苯二甲酸丁苄酯(BBP)。研究表明,PAEs的分子结构与雌性激素类似,被称作"环境荷尔蒙"。长期或高浓度接触可造成内分泌紊乱,影响男性生殖能力、促使女性早熟、危害儿童生殖系统。北京海关指出,由于PAEs增塑剂含量超标导致玩具不合格的占比最大。在玩具进出口环节,必须进行抽检PAEs增塑剂的含量以保证安全通关。现行玩具塑料中PAEs的检测方法,存在前期处理过程复杂、检测设备昂贵、对操作人员的专业要求较高等缺点,不利于PAEs的快速检测,迫切需要开发一种快速准确检测玩具塑料中PAEs含量的方法。以DEHP,DBP和BBP为研究对象,建立激光拉曼光谱快速筛查PAEs塑化剂的方法。首先,采用密度泛函理论(DFT)计算了三类塑化剂分子振动光谱,并与其在拉曼光谱仪上测得分子拉曼光谱比对认定,表明该方法对PAEs分子拉曼光谱特征峰的归属正确,能够用于玩具塑料样品的定性分析。其次,研究了拉曼光谱仪快速直接定量检测塑料中PAEs含量的方法。结果表明DEHP,DBP和BBP的含量与其特征峰强度呈线性相关,相关系数分别为0.98,0.99和0.99,表明PAEs定量分析的准确度较高。最后,采用该方法在不经任何前处理的条件下,测试市售玩具样品。通过优化采集过程中的背景扣除方法,获得拉曼光谱,确认了PAEs的种类为DEHP,并计算出DEHP的含量。同时,采用气相色谱-质谱法(GC-MS)准确检测样品中PAEs的种类及含量,两种方法的一致性令人满意。因此,采用激光拉曼技术,通过优化处理过程,可快速、无损检测塑料玩具中PAEs的种类及含量,能够大大缩短检测时间,节约测试成本。并有望应用于海关现场,提高通关速度。

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.