ICP-OES法测定电镀废水中铬等元素在排放限值的不确定度评定

摘要

重金属元素是电镀废水中的重要监测指标。以铬、铜、镍、铅、锌为例，建立了评定电感耦合等离子体发射光谱法测定电镀废水中重金属元素含量不确定度的数学模型，对标准溶液配制、仪器测量重复性、标准曲线拟合和样品预处理等不同因素进行了分析，评定出各不确定度分量。由不确定度分量的大小可知，样品预处理是影响测定结果不确定度的主要因素。当样品中铬、铜、镍、铅、锌等元素的浓度分别为《电镀污染物排放标准》中的排放限值0.5、0.3、0.1、0.1、1.0 mg·L-1时，其扩展不确定度分别为0.046、0.046、0.014、0.012、0.142 mg·L-1。%Heavy metals were important indicators for electroplating wastewater. Mathematic model was built for evaluating the uncertainty in determining the contents of heavy metals such as Cr,Cu, Ni,Pb and Zn in electroplating wastewater by ICP-OES. Factors that affect the uncertainty such as preparation of standard solution,repeated measurements,standard curve regression and sample prep-aration were discussed. Components of the uncertainty were also evaluated. Sample preparation was considered as the most important factor. The expanded uncertainties of Cr,Cu,Ni,Pb and Zn were 0. 046 mg·L-1 ,0. 046 mg·L-1 ,0. 014 mg·L-1 ,0. 012 mg·L-1 ,and 0. 142 mg·L-1 at their emission limits of 0. 5 mg·L-1 ,0. 3mg·L-1 ,0. 1mg·L-1 ,0. 1mg·L-1 ,and 1. 0mg·L-1 in E-mission Standard of Pollutants for Electroplating.