目的 对气相色谱内标法测定塑料制品中乙苯和苯乙烯含量进行不确定度评定，为塑料制品中乙苯、苯乙烯含量测定的准确性提供参考。方法 依据GB 31604.16—2016采用气相色谱内标法对塑料制品中乙苯和苯乙烯含量进行测定，根据相应的测量模型，分析不确定度主要影响因素的来源，并对各影响因素引入的相对标准不确定度进行评估。结果 测量塑料制品中乙苯、苯乙烯的扩展不确定度分别为(23.83±1.50)、(23.90±1.26)mg/kg(P=95%、k=2)。结论 结果表明，混标工作液配制、试样重复测量、气相色谱仪性能是影响乙苯和苯乙烯含量测量不确定度的主要因素，应选择精度高且量程合适的量具，加强气相色谱仪的期间核查，提高实验人员操作的熟练水平，进一步减小测量不确定度，使测量结果更为准确、可靠。

The work aims to determine the content of ethylbenzene and styrene in plastic products by gas chromatography internal standard method to provide reference for the determination accuracy of ethylbenzene and styrene in plastic products. The content of ethylbenzene and styrene in plastic products was determined by gas chromatography internal standard method according to GB 31604.16-2016. According to the corresponding measurement model, the sources of main influencing factors of the uncertainty were analyzed, and the relative standard uncertainty introduced by each influencing factor was evaluated. The expanded uncertainty of measurement of ethylbenzene and styrene in plastic products was (23.83±1.50) mg/kg and (23.90±1.26) mg/kg (P=95%, k=2) respectively. The results show that the preparation of mixed standard working solution, repeated measurement of sample and gas chromatograph are the main factors affecting the uncertainty of ethylbenzene and styrene content measurement. Measuring tools with high accuracy and appropriate range shall be selected. Periodic check and verification of gas chromatograph shall be strengthened. The proficiency level of experimental personnel shall be improved. The measurement uncertainty shall be further reduced, so that the measurement results would be more accurate and reliable.