Certified Reference Materials for the Phase Transition Temperature of Organic Substances Based on Anhydrous Sodium Acetate and Sodium Methansulfonate

The requirements for thermal analysis instruments are increasing in terms of extending the measurement ranges and improving their accuracy with scientific and technological progress in the field of metrological supervision, chemical, and pharmaceutical industries. The study of determining the melting point of organic substances is of particular relevance for the metrological support of the applied thermal analysis instruments and traceability to the base physical units. The purpose of the research was to test the possibility of using organic substances based on sodium acetate and sodium methanesulfonate as phase transition temperature standards for candidate materials to certified reference materials (CRMs) for the phase transition temperature traceable to the SI unit “temperature.” The procedure for measuring the phase transition temperature (melting point) was performed by differential scanning calorimetry using the thermal analyzer STA 449 F5 JUPITER from the State Primary Standard GET 173-2017. The determination of the CRM certified value was carried out in accordance with GOST ISO Guide 35-2015; the contributions to the uncertainty due to heterogeneity of the starting materials were evaluated; the short- and long-term stabilities of the materials were studied.