不确定度评定在焦磷酸法测定工作场所粉尘游离二氧化硅中的应用

Application of uncertainty evaluation in determining content of free silica in dust of workplace by pyrophosphoric acid method

[目的]对焦磷酸法测定工作场所粉尘游离二氧化硅质量分数进行不确定度评定。[方法]依据《测量不确定度评定与表示》(JJF 1059.1-2012)对《工作场所空气中粉尘测定第4部分:游离二氧化硅含量》(GBZ/T 192.4-2007)中焦磷酸法测定带来的不确定度的来源进行识别和评定,并合成不确定度。[结果]该方法测定过程中产生不确定度分量的主要来源为重复性和温度方面。不经氢氟酸处理的重复性方面相对标准不确定度为8.89×10^(-2),经氢氟酸处理后的重复性方面相对标准不确定度为5.90×10^(-2);温度计检定的温度方面相对标准不确定度为0.26×10^(-2),马弗炉校准的温度方面相对标准不确定度为0.12×10^(-2)。不经氢氟酸处理的工作场所粉尘游离二氧化硅质量分数合成标准不确定度为1.35%,扩展标准不确定度为2.70%;经氢氟酸处理后的工作场所粉尘游离二氧化硅质量分数合成标准不确定度为0.57%,扩展标准不确定度为1.14%。工作场所粉尘游离二氧化硅质量分数标准不确定度结果:不经氢氟酸处理为(15.18±2.70)%,经氢氟酸处理后为(9.66±1.14)%。[结论]在保持所使用的称量仪器具有良好的精密性、操作性和重复性基础上,应加强操作培训,熟悉操作处理全过程,以减少操作重复性和温度方面产生的不确定度叠加。

[Objective] To evaluate the uncertainty in determining free silica in dust of workplace by pyrophosphoric acid method. [Methods] According to the Evaluation and Expression of Uncertainty in Measurement（JJF 1059.1-2012） and the Method for Determination of Dust in the Air of Workplace Part 4：Content of Free Silica in Dust（GBZ/T 192.4-2007）,the uncertainty of pyrophosphoric acid method was sourced,evaluated and combined. [Results] The repeatability and temperature were the main sources of uncertainty components in the determination process. The relative standard uncertainty of repeatability without treatment by hydrofluoric acid was 8.89 × 10^-2,and the relative standard uncertainty of repeatability after treatment by hydrofluoric acid was 5.90 × 10^-2;the relative standard uncertainty of temperature by thermometer calibration was 0.26 × 10^-2,and the relative standard uncertainty of temperature by muffle furnace calibration was 0.12 × 10^-2. The combined standard uncertainty of free silica in dust at workplace without treatment by hydrofluoric acid was 1.35%,and the expanded standard uncertainty was 2.70%;the combined standard uncertainty of free silica in dust at workplace after treatment by hydrofluoric acid was 0.57%,and the expanded standard uncertainty was 1.14%. The results of the standard uncertainty of free silica in dust at workplace were（15.18 ± 2.70）% without treatment by hydrofluoric acid and（9.66 ± 1.14）% after treatment by hydrofluoric acid. [Conclusion] Except for maintaining the precision, operability and repeatability of all used weighing instrument,to strengthen the operation training and familiarity with the whole process of operation will reduce the uncertainty.