元素薄膜标样计量溯源技术路线探讨及验证

Discussion and Verification on the Technical Route of Traceability of Elemental Film Standard Samples

元素薄膜标样是X射线荧光光谱(XRF)法用于大气颗粒物样品中无机元素测定的必备实验用品。开发满足计量溯源要求的国产元素薄膜标样对于建立大气颗粒物元素XRF分析校准曲线,降低基层实验室用户采购薄膜标样费用具有重要意义。同时采用基于薄膜酸消解的等离子体发射光谱(ICP-OES)和基于直接测定的波长色散X射线荧光光谱(WD-XRF)两种方法,提出了对元素薄膜样品进行定值的技术路线,并以稀土元素薄膜样品的定值为例进行了验证。用镀膜固体粉末材料探讨了酸消解体系和ICP-OES分析方法的可行性,实验结果表明,稀土元素回收率93.3%~99.7%。基于酸消解-ICP-OES测定值建立的WD-XRF校准曲线具有良好线性关系,各元素相关系数0.9978~1.000。实现了WD-XRF测定结果应满足计量溯源要求的预期目的。基于同一批元素镀膜样品X射线荧光强度数据精密度,对镀膜工艺一致性进行了考察,相对标准偏差0.16%~1.5%。测量结果不确定度的评估数据表明,对于低含量元素薄膜样品,ICP-OES拟合模型误差是测量结果不确定度的主要分量。实验结果为后续开展元素薄膜标样协作定值奠定了基础。

Elemental thin film standard sample is an essential experimental material for the determination of inorganic elements in atmospheric particulate matter samples by X-ray fluorescence spectrometry(XRF).The development of domestic element film standard samples that meet the requirements of metrological traceability is of great significance for establishing XRF calibration curves in analysis of atmospheric particulate matter and to reduce the cost of purchasing film standard samples for users in XRF laboratories.A technical route is proposed to use both ICP-OES based on the acid digestion system and XRF by direct measurement to determine the element content in film samples,which is verified with the determination of rare earth elements in thin film samples.The feasibility of the acid digestion system and ICP-OES analysis method was explored with the coating solid powder material.The target element recovery is 93.3%—99.7%.The experimental results show that the WD-XRF calibration curve established based on the digestion-ICP-OES measurement results has a good linear relationship(i.e.the correlation coefficient of each element is 0.9978—1.000).The measurement result of the WD-XRF can meet the requirements of metrological traceability,as expected.Based on the precision of the fluorescence intensity data of the same batch of coated samples,the uniformity of the coating process was investigated.The relative standard deviation of intensity was from 0.16%to 1.5%.The evaluation data of uncertainty of measurement results shows that the fitting model errors of ICP-OES are the main components of uncertainty of measurement results for low content filter membrane samples.The experimental results laid the foundation for the subsequent collaborative analysis of standards for film samples of other series of elements.