Triboelectrification of Active Pharmaceutical Ingredients: Amines and Their Hydrochloride Salts

The triboelectric properties of active pharmaceutical ingredients (APIs) contribute to problems during the manufacturing of pharmaceuticals. However, the triboelectric properties of APIs have not been comprehensively characterized. In this study, the effect of salt formulation on the triboelectric properties of APIs was investigated. The triboelectric properties of three groups of amines, namely tertiary amines, purine bases, and amino acids, and their hydrochlorides were evaluated using a suction-type Faraday cage meter. Most of the hydrochloride salts exhibited more negative charges than the corresponding free bases, and the degree by which the triboelectric property changed upon hydrochlorination depended on the structural groups of the compounds. In the case of tertiary amines, the change in the zero-charge margin upon hydrochlorination was negatively correlated with the zero-charge margin of the free base. In contrast, hydrochlorination of the amino acids led to a significant change in the zero-charge margin. In most cases, salt formation also affected the triboelectric properties of API powders. Controlling the triboelectric properties of APIs solves various problems caused by the electrification of raw material powders and granules during the production of pharmaceuticals, thereby increasing the quality of produced pharmaceuticals.