ICP-OES测定纺织品中重金属Cr的不确定度评定

Evaluation of the Uncertainty for the Measurement of Chromium Content in Textile by ICP-OES

参照GB/T 17593.2—2007的检测方法,对纺织品中Cr含量测定的不确定度来源及评定方法进行了分析讨论,并以具体测量数据对不确定度进行了评定.结果表明,纺织品中Cr含量测定的不确定度主要来源于萃取液浓度的测量重复性和工作曲线拟合.在线性相关系数满足要求的前提下,工作曲线线性范围越宽,拟合的标准不确定度越大.对于任意给定的工作曲线,标准不确定度是常数,不随萃取液浓度改变.萃取液浓度很低时,相对不确定度大大增加,测量可靠性会大大降低.当纺织品中重金属Cr含量为0.60 mg/kg时,标准合成不确定度为0.017 mg/kg,扩展不确定度为0.04 mg/kg.

Referring to the test method specified in GB/T 17593.2-2007,the sources and evaluating methods of the uncertainty of the content of chromium in textile measured by ICP-OES are analyzed,and experimental data obtained in this study are used to estimate the uncertainty of measured chromium content.The results show that the measure repeatability and the standard calibration curve fitting are the two main sources resulting in the uncertainty.Though the linear correlation coefficient of the calibration curve meets the required accuracy,a wider calibration range would lead to a higher uncertainty uf( c) of the calibration curve fitting.For any given curve,the uf( c) is a constant and does not change with the variation of the chromium content.When the chromium content is too low,the relative uncertainty would increase significantly,resulting in unreliable measurement.In this study,the Cr content in the textile is 0.60 mg/kg,the estimated combined uncertainty and expanded uncertainty are respectively 0.017 mg/kg and 0.04 mg/kg.