STUDIES ON PERCENTAGE DISTRIBUTION OF DRUGS OF TERTIARY AMINE IN AQUEOUS SOLUTIONS OF ACIDS

This paper describes the percentage distribution (PD) of 8～11 amine drugs between aqueous solutions of six inorganic and eight organic acids and CHCl₃. The following results were obtained: when the molecular Weight of the acid did not exceed that of the amine, the PD of amine depended mainly upon the molecular structure of the tertiary amine. For different acids, the order of arrangement of the PD of the amines was the same. In the case of inorganic acid, the order of the PD of the same amine in aqueous solutions of different acids was: HClO₄≥HBr>HNO₃≥HCl>H₂SO₄>H₃PO₄; monobasic acid>dibasic acid>tribasic acid, and the PD of tertiary amines in the monobasic acid solution varied approximately with the molecular weight of acid. In aqueous solutions of organicf acids, when extracted with CHCl₃, the PD of the same tertiary amine became larger with increasing number of carbon atom or lipophilic group of acid, and became smaller with increasing hydrophilic group of the acid. Only at low concentration of acid, the PD of tertiary amines was related to the pKa of the acid. Difference of PD of tertiary amines in aqueous solution of acid was larger than that in neutral and alkaline aqueous solution, thus, it could be used in separation of tertiary amines. The results indicate that even in strong inorganic acid solutions many tertiary amine salts can be extracted with CHCl₃.