validated colorimetric assay of clonidine hydrochloride from pharmaceutical preparations

clonidine hydrochloride is an antihypertensive agent used for migraine prophylaxis, attention deficit hyperactivity disorder, menopausal flushing and tourette syndrome. the quantity of the active substance in pharmaceutical preparations must be within specific limits, in agreement with the respective label claim. therefore, the aim of this study was to establish the conditions for two spectrophotometric methods for clonidine determination, based on the formation of the ion pair complex between clonidine hydrochloride and thymol blue/bromophenol blue. a jasco uv-vis 530 spectrophotometer was used for the analysis and the maxim absorbance was measured at 418 nm/448 nm against blank solution. after validation, the methods were used for quantification of clonidine hydrochloride in two commercial samples (tablets). the recovery of active substance varies between 98.06 and 100.13 % without interferences from the excipients.