Triiodide ion and alizarin red S as two new reagents for the determination of clotrimazole and ketoconazole.

The reactions of a triiodide ion and alizarin red S with two important antifungal drugs containing an imidazole ring (ketoconazole (KC) and clotrimazole (CT)) have been studied for the development of two simple, rapid, sensitive and accurate indirect titrimetric and extractive-spectrophotometric methods for determining the concentration of these drugs. Spectroscopic studies and chemical analysis showed that the protonated forms of KC and CT react with triiodide ion forming highly stable and insoluble ion-pair products such as (KCH(2))(I(3))(2) and (CTH)I(3). Formation of ion-association complexes have been applied to the development of an indirect visual titrimetric method for the determination of KC and CT over the range 10(-5)-10(-2) M. The extractive-spectrophotometric method is based on the formation of (1:1) ion-association complexes between drugs and alizarin red S as chromogenic reagent in acidic citrate buffer that are extractable into chloroform with an absorption maximum at 425 nm. The system obeyed Beer's law in the concentration range 2.5-50 and 2.7-80 microgram ml(-1) for CT and KC, respectively. The proposed methods were applied for the analysis of the studied drugs in pure forms and their commercial preparations. Results are in good agreement with those obtained by official methods.