容量法测定生活饮用水总硬度的不确定度评定

根据生活饮用水总硬度测定的方法步骤,对采用EDTA容量法测定总硬度的测量不确定度进行了评定。从锌标准溶液配制、Na2EDTA标准溶液标定、样品溶液测定3个环节归纳了不确定度的来源。通过建立数学模型,给出了测定实验室自来水总硬度的各不确定度分量的详细评定过程,由各不确定度分量求得了总硬度的合成标准不确定度及扩展不确定度,当置信水平95%时,得出实验室自来水总硬度的测量不确定度为246.9±1.02mg·L-1。

Uncertainty evaluation in determination of total hardness in drinking water by volumetric method

According to the determination methods and steps of total hardness of drinking water, the uncertain-ty in measurement for the determination of total hardness by EDTA volumetric method was evaluated. The source of uncertainty was summarized through the following three aspects：the preparation of zinc standard solution, cali-bration of Na2EDTA standard solution and the determination of the sample solution. The detailed evaluation pro-cess of uncertainty components in measurement of total hardness in laboratory water was given by establishing mathematics model. Synthesis standard uncertainty and expanded uncertainty of total hardness were obtained by the uncertainty components. The uncertainty of measurement of total hardness is 246.9 ＆#177;1.02mg＆#183;L-1 in the level of 95%confidence level.