EDXRF法快速测定玩具塑料中8种有害元素

铬、砷、硒、镉、锑、钡、汞和铅8种有害元素是玩具安全领域必检项目。目前，标准方法大多需采用湿化学法处理样品，再用仪器进行测试，前处理过程复杂，耗时长、成本高。EDXRF法具有无须样品前处理、对样品非破坏性、成本低、效率高等优点，已广泛用于电子电气产品中有害物质的快速筛选分析，但由于玩具材料和待测元素种类多，大多元素限量较低，目标元素间存在重叠干扰，导致难以准确测试，尚未见应用于玩具中8种有害元素的测定。通过研究分析线、滤光片、管电压、分析时间等测试条件的选择和样品厚度对结果的影响，并根据目标元素的特性，确定了最佳的3种条件组合方式。通过经验系数法校正了塑料中分析元素相互之间引起的吸收-增强效应，利用Rh康普顿散射线作为内标校正了样品的颗粒度效应，并通过干扰重叠系数法校正了元素间谱线重叠干扰。根据玩具常用塑料样品基体类型特性，选用聚乙烯（PE）和聚氯乙烯（PVC）两类塑料标准样品分别制作工作曲线，建立了EDXRF法快速测定玩具塑料中8种有害元素含量的新方法。各元素在7.6～1 298 mg·kg-1范围内线性良好，方法检出限在0.5～37 mg·kg-1之间，能够满足目前玩具安全标准限量筛选要求。采用PP，PE，ABS和PVC等不同玩具塑料样品验证了方法的准确度和精密度，并将样品测试结果与样品参考值比较，计算相对误差均在25%以内，除某样品中个别元素RSD(n=6)在9%~15%稍大外，其他样品各元素的RSD(n=6)均在6%以内，精密度较好。如将单个条件的测试时间从30 s延长到2 min后，所有样品测定结果RSD均可降至5%以下。本方法操作简便、成本低、快速、准确，可用于玩具塑料中有害元素的快速筛选分析。

Rapid Determination of Chromium,Arsenic,Selenium,Cadmium,Antimony,Barium,Mercury and Lead in Toy Plastics by Energy Dispersive X-Ray Fluorescence Spectrometer

As the most important items in the field of toy safety,8 harmful elements(chromium,arsenic,selenium,cadmium,antimony,barium,mercury and lead)were determined by the wet chemical method of sample preparation and instrumental analysis in current most of standard methods,but the pre-treatment process is complicated,time-consuming and costly.EDXRF has the advantages of simple pre-processing,non-destructive,and high efficiency.It is often used widely for the screening of harmful elements in electronic and electrical products.However,due to the variety of elements and toys materials,the lower limits,and the overlapping interference between target elements,it is difficult to use EDXRF to test accurately 8 certain elements in toys up to now.A new rapid method for measuring the content of eight elements in toy plastics by EDXRF was established.The measurement conditions of target elements,such as analytical line,tube voltage,analytical time and sample thickness,were investigated.According to the characteristics of the target elements,3 combinations of filter and tube voltage were selected finally.This method can complete the test of 8 elements within 135 s totally for one daily sample.The interference from spectra overlap was corrected by the interference coefficient method.The matrix effect was corrected by experience coefficients method,using rhodium scattered radiation as internal standard simultaneously.Polyethylene(PE)and polyvinyl chloride(PVC)were selected as the standard samples to make the working curve according to the characteristics of the common plastic sample matrix of toys.The calibration curve method was effective.For the target elements,the detection limits of this method were between 0.5 and 37 mg·kg^-1.It can meet the screening limits requirements of most of the national standards of safety of toys.The accuracy and precision of the method were evaluated by several materials(PP,PE,ABS,PVC).The relative error(n=6)is within 25%,which indicates that the method has good accuracy.The RSD(n=6)is within 6%,except for some RSDs of individual elements in individual samples within 9%~15%,with good precision.If the test time is extended from the 30 s to 2 min,all RSDs can be reduced to less than 5%.The method can be applied to rapid screening detection of the eight harmful elements in all kinds of toy plastics.