Sensitive spectrophotometric methods for quantitative determination of chlorprothixene in pharmaceutical dosage form

Simple and sensitive UV-VIS spectrophotometric methods for the determination of chlorprothixene hydrochloride have been developed. One of them is based on the oxidation of chlorprothixene (CPT) by ammonium metavanadate with the formation of colourless product. The second method involves the formation of ion-pair between the drug under investigation and inorganic complexes of titanium (IV) thiocyanate followed by its extraction with mixture of butanol-chloroform (1:9, v/v). The optimum conditions for the oxidation of CPT or ion-pair formation are established. The studies are examined by UV-VIS, IR or NMR spectroscopy. The methods permit the determination of CPT over the concentration range of 2.5-25 mug/ml and 4-35 mug/ml using ammonium metavanadate or the titanium (IV) thiocyanate complex, respectively. The methods are rapid, highly reproducible and accurate with +/- 0.8%. The methods are applicable to the assay of the drug under investigation in different dosage forms and the results are in good agreement with those obtained by the official methods. Common excipients used as additives to active ingredient in pharmaceutical preparations do not interfere in the proposed methods. The extractive spectrophotometric method can be applied to the determination of chlorprothixene hydrochloride in tablets after solid phase extraction (SPE).