Potentiometric determination of captopril.

A rapid, accurate and reproducible method for the potentiometric determination of captopril in aqueous solution, is described. The method is based on the reaction of the thiol and the carboxylic group of captopril with silver ions whereby an equivalent amount of the acid is liberated; thereafter, the amount of captopril is determined by the potentiometric titration with sodium hydroxide. This method can be applied also for direct determination of captopril content in tablets.

Conductometric determination of methenamine.

A method of conductometric titration for determination of methenamine is presented. An aqueous solution of silicotungstic acid is used as titrant. The acid and methenamine form an insoluble compound in which the molar ratio of the acid to methenamine is 1:4. Conductometric curves were obtained, the shapes of which are suitable for accurate and reproducible determination of the end point of titration. The results show reasonable accuracy. Good reproducibility was achieved even when small quantities of methenamine had to be determined.

[Conductometric determination of meclozine hydrochloride (author's transl)]. / Konduktometrische Bestimmung von Meclozinhydrochlorid.

The authors describe a conductometric method for determining meclozine hydrochloride as a pure substance and in tablets. The titration is performed with perchloric acid in glacial acetic acid and in ethanolic solution with ethanolic potassium hydroxide solution. As a result, conductometric curves are obtained, the forms of which are suited for the accurate reproducible determination of the end point. The method permits to estimate small amounts of meclozine hydrochloride.