Applications of aqueous thermometric titration to pharmaceutical analysis.

Aqueous thermometric titration with standard HCI, NaOH, or AgNO 3 as titrant was used successfully for the analyses of aminophylline (ethylenediamine and theophylline), chlorpheniramine maleate, chlorpromazine hydrochloride, hydrochlorothiazide, and niacinamide. Most of the determinations were based on titration volumes. In cases where the curvature of the enthalpogram in the vicinity of the end point was severe, the quantitative result was derived from the temperature change due to the reaction. Exploratory studies of the applicability of simple aqueous thermometric titration, without prior separation of ingredients, to the analysis of solid and liquid dosage forms of the above compounds were conducted. With all but 1 of the solid dosage forms investigated, no interferences from inert ingredients were observed. In some of the liquid dosage form systems studied, the vehicles interfered with the titrations, while in others they did not.