酚试剂法测定能力验证样品中甲醛含量不确定度评定

Evaluation on uncertainty for determination of formaldehyde in proficiency testing sample by phenol reagent method

目的通过对能力验证考核样品中甲醛含量不确定度评定,系统分析影响测定结果可靠性的关键环节和主要因素,为有效提高检测工作质量提供依据。方法根据CNAS-GL06:2006《化学分析中不确定度的评估指南》建立数学模型,计算各不确定度分量,由此得出合成不确定度和扩展不确定度。结果样品中甲醛含量及扩展不确定度为(0.676±0.028)mg/L(k=2,置信概率95%)。结论该次测定不确定度主要来源于标准溶液配制引入的标准不确定度,其次为绘制工作曲线的变动性不确定度分量。因此,实验室应规范做好标准溶液的配制、工作曲线的绘制等几个关键环节,以保证测量结果准确、可靠。

[Objective] Through the evaluation on uncertainty for determination of formaldehyde in proficiency testing sample,to analyze the key links and the main factors that influence the accuracy of the test results,provide the basis for effectively improving the quality of the detection work. [Methods]The mathematical model was established according to the Guidance on Evaluating the Uncertainty in Chemical Analysis（CNAS-GL06：2006）,to calculate the uncertainty components, and the combined uncertainty and expanded uncertainty were derived from the standard uncertainty components.[Results]Formaldehyde content in the proficiency testing sample and the expanded uncertainty were（0.676 ±0.028） mg/L（k =2,95% confidence probability）. [Conclusion]The uncertainties in this test mainly come from the standard solution preparation and working curve fitting. Therefore,the laboratory should regulate the key links of preparation of standard solution and plotting of working curves to get accurate and reliable results.