示差走査熱量計を用いる凝固点降下法による有機塩素系化合物の純度分析における不確かさ評価

抄録

Purity analysis using the freezing-point depression method is qualified as a measurement method traceable to the International System of Units. In particular, it is well-known that it is one of the analytical methods for which absolute quantities can also be obtained for high-purity organic compounds. However, the evaluation of commercially available raw materials for standard solutions is normally performed using chromatography, and few examples exist of the application of the freezing-point depression method. In this study, we applied the freezing-point depression method to perform a purity analysis of polychlorinated biphenyls and other organochlorine compounds, using a differential scanning calorimeter. We then evaluated the uncertainties to examine its practical applicability. The measurement results obtained in this study for the compounds used indicated purity levels of between 99.7% and 99.9%. When we assessed uncertainty, the uncertainty for the unit of purity obtained using the freezing-point depression method, after taking into account the uncertainty in conversion from the amount-of-substance fraction to the mass fraction, could be evaluated at a practically viable level of 0.2% to 0.4%. We expect that the uncertainty evaluation method proposed here can be used to perform a quantitative evaluation of the practicality of applying a differential scanning calorimeter to purity analyses of raw materials for standard solutions.