环境监测化学需氧量测定结果质量的影响因素研究

Research on Factors Influencing the Quality of Chemical Oxygen Demand Measurement Results in Environmental Monitoring

根据检测标准HJ 828—2017对不同浓度样品均进行9次重复测定,在测定过程中将不同平行测定次数的测定结果运用简化GUM法对引入的不确定度进行评定分析,根据引入的不确定度大小判定影响测定结果质量的主要因素。实验结果表明:重复测定次数不同低浓度样品测定结果质量均低于高浓度样品,重复测定次数差异相对标准不确定度比值为1.7~3.7倍;测定过程中测定结果质量的主要影响因素是样品测定的重复性以及对测定结果进行修约,重复测定次数差异其贡献度占比介于48.8%~87.1%,其中样品测定重复性影响比测定结果修约大,尤其在测定次数小于3次时最为明显。

According to the detection standard HJ 828—2017,samples of different concentrations were subjected to 9 repeated measurements.During the measurement process,the results of different parallel measurements were evaluated and analyzed using the simplified GUM method for the introduced uncertainty.The main factors affecting the quality of the measurement results were determined based on the magnitude of the introduced uncertainty.The experimental results show that the quality of low concentration samples with different repetition times is lower than that of high concentration samples.The relative standard uncertainty ratio for different repetition times is 1.7~3.7 times;The main influencing factors on the quality of measurement results during the measurement process are the repeatability of sample measurements and rounding off the measurement results.The contribution rate varies from 48.8%to 87.1%depending on the number of repeated measurements.The repeatability of sample measurements has a greater impact than rounding off the measurement results,especially when the number of measurements is less than 3.