ION-PAIR FORMATION OF BI(III)-IODIDE WITH SOME NITROGENOUS DRUGS AND ITS APPLICATION TO PHARMACEUTICAL PREPARATIONS

A systematic spectrophotometric study on the ion-pair formation of Bi( III)-iodide with amineptine hydrochloride: piribedil and trimebutine m aleate is carried out. The optimal experimental conditions pH, concent ration of BI(III) nitrate, potassium iodide; and the nature and amount of organic solvent have been studied. The ion pairs are soluble in 1, 2-dichloroethane and the optimum pH range is 2.0-2.8. By application o f the methods of Sommer and Job involving non-equimolar solutions, the conditional stability constant (log K') of the Bi(III)-piridedil ion pair (1:1) at the optimum pH of 2.4 and an ionic strength (mu) 0.1 M, was found to be 5.436. The validity of Beer's law has been tested in t he concentration range 5-50 mu g ml(-1) in the organic layer, the rela tive standard deviation is less than 1%. The method is applied to the determination of these drugs in tablets without interference. (C) 1998 Elsevier Science B.V.