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目的对直接沉淀滴定法测定鱿鱼丝中氯化钠的含量进行不确定度评定。方法对氯化钠含量测定过程中各影响因素包括称量、样品溶液定容、测定试液体积、标准滴定溶液浓度、滴定过程等进行分析评定。结果鱿鱼丝中氯化钠检测的不确定度主要由标准滴定溶液浓度的不确定度分量和重复性试验误差引入,而标准滴定溶液浓度的不确定度分量贡献最大。通过对标准溶液浓度的不确定度评定,发现其主要不确定度由称量过程中的不确定度引入。该方法检测鱿鱼丝中氯化钠的扩展不确定度为0.043%。本实验测定的氯化钠含量结果为(2.49±0.043)%(P=95%,k=2)。结论本方法可为评定食品中氯化钠含量的测量结果和方法的可靠性提供科学依据。
OBJECTIVE To evaluate the uncertainty of determination of sodium chloride in squid silk by direct precipitation titration. Methods The influencing factors in the determination of sodium chloride content include weighing, volume of sample solution, volume of test solution, concentration of standard titration solution and titration process. Results The uncertainty of sodium chloride detection in squid silk was mainly caused by the uncertainty component of the standard titration solution concentration and the repetitive test error, while the uncertainty component of the standard titration solution concentration contributed the most. Through the evaluation of the uncertainty of the standard solution concentration, it is found that the main uncertainty is introduced by the uncertainty in the weighing process. The uncertainty of the method for detecting sodium chloride in squid silk is 0.043%. The sodium chloride content in this experiment was (2.49 ± 0.043)% (P = 95%, k = 2). Conclusion This method can provide a scientific basis for the measurement of the content of sodium chloride in food and the reliability of the method.