Study on the Influence of Moisture on DSC Melting Point Analysis

OBJECTIVE  To study on the influence of moisture on differential scanning calorimetry(DSC) melting point analysis.

METHODS  In the general method of DSC melting point analysis, the melting range with 30 ℃ of start temperature and 10 ℃·min⁻¹ heating rate, the atmosphere was nitrogen and the dry gas flow was 50 mL·min⁻¹. In the optimization method, the start temperature was 20 ℃ before melting temperature, the heating rate was adjusted to 1 ℃·min⁻¹, and the other parameters remained unchanged.

RESULTS  Without drying test samples, the melting point could be detected accurately in the general method of DSC melting point analysis for the imidazole, norepinephrine hydrochloride and methylthioneostigmine samples with moisture content of 4.3%, 5.3% and 6.1% respectively, and in the optimization method of weakening the influence of moisture, the melting point could be analyzed exactly for the homologous samples with moisture content of 9.0%, 6.0% and 7.1% respectively.

CONCLUSION The DSC method for melting point analysis need not to dry samples, and there is no difference between the conventional DSC method and the capillary method that need to pre dry samples. The optimized DSC method further reduced the impact of adsorbed moisture and has wider applicability.