目的了解水样中硝酸根离子含量的不确定度来源,从而对不确定度进行评定。方法按照测定程序,建立数学模型,根据不确定度传播规律,计算出相对和绝对扩展不确定度。结果水样中硝酸根离子的相对扩展不确定度为4.06%(k=2)。结论水样中硝酸根离子的相对扩展不确定度为4.06%(k=2)。 Objective To understand the sources of uncertainty of nitrate ion content in water samples and evaluate the uncertainty. Methods According to the measurement procedure, a mathematical model was established, and the relative and absolute expansion uncertainties were calculated according to the law of propagation of uncertainty. Results The relative expansion uncertainty of nitrate ions in water samples was 4.06% (k = 2). Conclusions The relative expansion uncertainty of nitrate ions in water sample is 4.06% (k = 2).