常量法测定螺旋藻片中氮含量的不确定度评定

评定螺旋藻片中氮含量测定的不确定度。方法 采用《中国药典》2015年版第四部氮测定法中第一法(常量法)，测定出螺旋藻片中的含氮量。根据测量不确定评定的要求与表示的要求，通过获得的检测数据对螺旋藻片中氮含量测定的不确定度进行评定。结果 当氮含量的结果为：20.59mg/片时，常量法测定螺旋藻片氮含量的合成标准不确定度为0.196mg/片，扩展不确定度为0.39mg/片，螺旋藻片中氮含量测定的结果为：(20.59±0.39)mg/片，（k=2,p=95%）。结论 在测定过程中，测量不确定度的主要来源于试样测定重复性实验引入的不确定度和试样滴定过程引入的不确定度。因此, 对常量法测螺旋藻片氮含量的不确定度评定时, 应控制好试样的消化、蒸馏，同时控制好试样的滴定，以确保数据的准确可靠。

Uncertainty evaluation for the determination of nitrogen content in Spirulina tablets by constant method

Objective To evaluate the uncertainty for the determination of nitrogen content in Spirulina tablets by constant method. Methods The first method (constant method) in the fourth nitrogen determination method of the Chinese pharmacopoeia 2015 edition was used to determine the nitrogen content in Spirulina tablets. The uncertainty of determination of nitrogen content in spirulina tablets was evaluated through the obtained test data. Results When the nitrogen content was 20.59 mg/tablet, the standard uncertainty for the determination of nitrogen content in Spirulina tablets by constant method was 0.197 mg/ tablet, the extended uncertainty was 0.39 mg/tablet, and the determination result of nitrogen content in Spirulina tablets was (20.59±0.39) mg/tablet (k=2, P=95%). Conclusion The uncertainties of measurement mainly come from the repeatability experiment of sample determination, sulfuric acid standard solution, titration process, digestion and distillation of sample, and the uncertainty contribution of sample weighing is small.