旋光法测定木薯中淀粉含量不确定度评定

对采用旋光法测定木薯中的淀粉含量的不确定度进行评定。建立测量模型,分析确定木薯中淀粉含量的不确定度来源,并对测量过程中的不确定度分量进行逐层分析与合成,当木薯的淀粉含量为50.20 g/100 g时,得到其合成标准不确定度和扩展不确定度分别为0.16、0.32 g/100 g。结果表明,木薯总旋光度重复测定对不确定度贡献最大,总旋光度测定过程产生的不确定度也不容忽视,试样称量对总不确定度的贡献最小。实验结果可为采用该方法测定木薯中淀粉含量的质量控制提供理论依据。

Uncertainty Evaluation for the Determination of Starch Content in Manihot esculenta by Polarimetric Method

In this paper, the measurement uncertainty for the determination of starch content in the dried residue left afterstarch extraction from Manihot esculenta by polarimetric method was evaluated. Each uncertainty component during theprocess of measurement was modeled. The main sources of uncertainty were identified and analyzed. The impact of everyuncertainty component on the measurement uncertainty was estimated. Based on quantitative analysis of every uncertaintysource, the relative standard uncertainty of the measurement results was obtained. The starch content in the Manihotesculenta residue was still as high as 50.20 g/100 g, with a combined standard uncertainty of 0.16 g/100 g and an expandeduncertainty of 0.32 g/100 g. The evaluation indicated that repeated determinations of the total optical rotation of the Manihotesculenta residue made the most important contribution to the combined relative standard uncertainty. The influence ofrepeated determinations of the optical rotation of its alcohol-soluble fraction could not be neglected. The effect of sampleweighing was minimal. This evaluation can provide a theoretical basis for the quality control of starch content determinationin Manihot esculenta.