Study on the Correlation Among Hygroscopicity, Solubility and Specific Surface Area of the Chemical Reference

OBJECTIVE To preliminarily study the correlation among the hygroscopicity, solubility and specific surface area of drug (chemical reference). METHODS The moisture adsorption kinetics of the 631 drugs in the Chemical Reference Map Set-Dynamic Water Adsorption was analyzed, and the maximum hygroscopic rate (rate of mass change), specific surface area, water solubility and ethanol solubility of RH80% after 180 min was input into Excel formats. The relationship of the average moisture absorption rate, average specific surface area, solubility in aqua, solubility in ethanol was analyzed. The hygroscopic functional groups of hygroscopic drugs and moisture release behavior were analyzed. The hygroscopic strength of different hygroscopic functional groups was preliminarily compared. RESULTS The specific surface area of the 631 drugs was 0-396.11 m²·g^-1, the moisture absorption rate was 0.02%-81.00%. The average moisture absorption rate of the drug was positively correlated with the average specific surface area, water solubility and hygroscopic functional groups, while the correlation between the average hygroscopic rate and the solubility of ethanol, the same solubility in water and ethanol was complicated. There might be 20 hygroscopic functional groups including amino, hydroxyl, carboxyl, sodium, potassium, ammonium, aluminum silicate, oligosaccharide, etc. The appearance was observed that the drug might do not liberate moisture, liberate moisture partially or liberate moisture completely in a low relative humidity environment after moisture absorption. The relationship between drug solubility and average specific surface area:when the water solubility was more than slightly soluble, the correlation was negative, whereas showed positive correlation. When the ethanol solubility was above the slightly soluble, the correlation was not correlated, and below, negative correlation. CONCLUSION There is a correlation between the hygroscopicity, solubility and specific surface area of the chemical reference, which provides a reference for the moisture-proof process of drugs and the technology to improve the dissolution of insoluble drugs.