热裂解处理样品-气相色谱-质谱法应用于聚苯乙烯中聚氯乙烯的定性和定量检测

Application of GC-MS to Qualitative and Quantitative Inspection of Polyvinyl Chloride in Polystyrene with Pyrolytic Splitting of Sample

为了间接减少聚氯乙烯(PVC)中添加剂对环境和人体健康的危害,采用热裂解处理样品-气相色谱-质谱法对聚苯乙烯(PS)中的PVC进行了定性和定量检测。称取聚苯乙烯样品1.0mg置于样品舟中,按单击裂解模式在500℃条件下裂解。在裂解过程中,样品中的PVC首先脱掉其主链上的HCl,然后主链断裂并环化形成苯、苯乙烯、甲苯、茚、萘、苊、芴、蒽等芳香族化合物,裂解产物通过DB-5MS色谱柱分离,并进入质谱分析,得到各裂解产物的指纹谱图。在PVC阳性样品谱图中所得到的样品的裂解峰以及保留时间与PVC标准品所得的相同,可定性判定样品中存在PVC,且PVC的特征裂解峰的丰度比与PVC标准品的裂解峰的丰度比一致,说明样品中不存在干扰PVC测定的物质,此时,可通过测定裂解产物苯对PVC进行定量测定。用自行配制的工作曲线用样品制作工作曲线,测得PVC裂解产物中苯的峰面积与PVC质量在0.5~50μg之间呈线性关系,其检出限(3S/N)为106mg·kg^-1。对含PVC 20μg的工作曲线用样品测定6次,计算得相对标准偏差(n=6)为3.6%。对9个PVC阳性样品进行回收试验,测得其回收率在84.0%以上。

In order to indirectly reduce the harm of polyvinyl chloride(PVC)additives to the environment and human health,the qualitative and quantitative analysis of PVC in polystyrene(PS)was made by application of GCMS with pyrolytic splitting of sample.1.0 mg of polystyrene sample was taken and pyrolyzed in a sample boat at500℃to split the PVC in the sample by dropping the HCl from the main chain,and breaking the chain to give cyclic aromatic compounds of benzene,styrene,toluene,indene,haphthalene,acenaphthene,fluorene and anthracene.These split products were separated by passing through the DB-5 MS chromatographic column and measured by MS,obtaining the finger-print spectra of the split products.The spectra of split products of PVC and their retention times of the self-prepared PVC positive samples found were in consistence with those found in the spectra given by PVC standard,qualitative existence of PVC in the self-prepared PVC positive samples could be deduced.And it was found that the abundance ratios of the specific split peaks of PVC in self-prepared PVC positive samples were in consistence with those of the PVC standard,showing that there was no interfering substance present in the analysis of PVC,hence the split product of benzene could be determined for the quantification of the PVC in the sample.Self-prepared samples of PVC were used to prepare the working curve in the same way as the sample analysis,and linear relationship was obtained between mass of PVC in the range of 0.5 to 50μg and values of peak areas of benzene(m/z 78).Detection limit(3 S/N)found was 106 mg·kg-1.Six parallel determinations of a known sample containing 20μg of PVC for working curve were carried out and value of RSDs(n=6)found was3.6%.Recovery was made by analyzing the 9 self-prepared PVC positive samples with known PVC contents,giving values of recovery over 84.0%.