6项环境监测分析方法标准中钴、铬、钼、钛的不确定度分析及其在达标判定中的应用

Measurement Uncertainty and Applicability in Conformity Assessment of Co,Cr,Mo,Ti for 6 Environmental Monitoring Analytical Method Standards

研究依据测定不确定度的基本理论和ISO 21748:2017《采用重复性、再现性和正确度评估测量不确定度的导则》,提出了基于中国环境监测分析方法标准多家实验室验证中已获得的数据计算合成标准不确定度的方法,将方法标准中规定的重复性、再现性等指标与合成标准不确定度进行了衔接。分析了近年发布的6项水质监测分析方法标准中钴、铬、钼、钛等4种金属元素的相对合成标准不确定度,结果表明:被测量的浓度是影响方法标准测量不确定度的重要因素。对于火焰原子吸收分光光度法(FAAS)和石墨炉原子吸收分光光度法(GAAS),样品浓度为方法标准测定下限3倍左右时,测定结果的相对标准不确定度可保持在15%以下;对于电感耦合等离子体发射光谱法(ICP-AES),样品浓度为方法标准测定下限3~5倍时,测定结果的相对标准不确定度为12%~17%;对于电感耦合等离子体质谱法(ICPMS),钛元素浓度为测定下限3倍左右时,相对标准不确定度在15%以下,而钴、铬、钼的浓度在测定下限40~100倍以上时,相对标准不确定度在15%以下。6项方法标准可分别用于《地表水环境质量标准》(GB 3838—2002)以及22项水污染物排放标准钴、铬、钼、钛的达标监测。

The present research obtained the general formulation of the combined standard measurement uncertainty using the interlaboratory validation results in the environmental monitoring analytical method standards.The formulation of measurement uncertainty was based on the general rules for measurement uncertainty evaluation and ISO 21748: 2017 Guidance for the Use of Repeatability,Reproducibility and Trueness Estimates in Measurement Uncertainty Evaluation.The formulation complied the measurement uncertainty with measurement repeatability and reproducibility.The research evaluated the relative standard measurement uncertainty of Co,Cr,Mo,Ti for 6 environmental monitoring analytical method standards and results showed that the concentration of the measurands were main factors contributed to measurement uncertainty.For FAAS and GAAS,when concentrations of the measurands were about 3 times of the minimum quantitative detection limits(MQDL),the relative standard measurement uncertainty was less than 15%.For ICP-AES,when concentrations of the measurands were about 3-5 times of MQDL,the relative standard measurement uncertainty was 12%-17%.For ICP-MS,when concentrations of Co,Cr,Mo were about 40-100 times of MQDL and Ti were about 3 times of MQDL,the relative standard measurement uncertainty were less than 15%.The 6 methods could be applied in conformity assessment monitoring for Co,Cr,Mo,Ti in Surface Water Environmental Quality Standards and 22 water pollutants emission standards.