快速消解分光光度法测定低浓度水样化学需氧量的不确定度评定

Uncertainties of COD Determination in Low Concentration Water Samples with Rapid Digestion Spectrophotometric Method

运用测量不确定度评定的方法和程序,分析了快速消解分光光度法(HJ/T 399-2007)测量水质化学需氧量测试过程中不确定度的来源,主要是标准溶液配制、标准曲线拟合、样品重复测定、分光光度计、取水样体积这五部分引入的不确定度。本次测量相对合成不确定度为0.027;最大的相对不确定度分量是标准曲线拟合引起的,相对不确定度为0.015;最小的相对不确定度分量是取水样体积引起的,相对不确定度为0.003 2;本次测量结果为:56.0 mg/L±3.04 mg/L,k=2。

The sources of uncertainty in analyzing chemical oxygen demand （COD） in water by rapid digestion spectrophotom- etry （ HJ/T 399 - 2007） include, preparation of standard solution, standard curve fitting, repeat testing of samples, spectropho- tometer and water sample volume. The uncertain degree of this study is 0. 027 ; the most important relative uncertainty component was the standard curve fitting, with the relative uncertainty of 0. 015. The minimum relative uncertainty component was water sam- ple volume, with relative uncertainty degree of 0. 003 2. The results of this measurement is 56. 0 ＋ 3.04 mg/ L, k = 2.