Spectrophotometric and chromatographic simultaneous estimation of amitriptyline hydrochloride and chlordiazepoxide in tablet dosage forms.

A binary mixture of amitriptyline HCl and chlordiazepoxide was determined by three different methods. The first method involved determination of amitriptyline HCl and chlordiazepoxide using the first derivative spectrophotometric technique at 219 and 230 nm over the concentration ranges of 1-20 and 2-24 mug/ml with mean accuracies 100.9+/-0.87 and 99.2+/-1.0%, respectively. The second method was reversed-phase high performance liquid chromatography using methanol: acetonitrile: 0.065 M ammonium acetate buffer (50:20:30, v/v/v), final pH adjust to 5.5 +/- 0.02 with ortho phosphoric acid as the mobile phase and was pumped at a flow rate of 1.0 ml/min. Quantification was achieved with ultraviolet detection at 240 nm over concentration ranges of 0.25-4 and 0.1-1.6 mug/ml; mean accuracies were 100.55+/-0.62 and 100.71+/-0.81%, respectively. The third method utilized high performance thin layer chromatography method in tablet dosage form. The method was based on separation of the two drugs followed by densitometric measurements of their spots at 240 nm. The separation was carried out on Merck thin layer chromatographic aluminium sheets of silica gel 60 F254 using carbon tetrachloride: acetone: triethylamine (6:3:0.2, v/v/v) as mobile phase. The linearity was found to be in the range of 50-600 and 20-240 ng/spot for amitriptyline hydrochloride and chlordiazepoxide, respectively. The methods were successively applied to pharmaceutical formulation because no chromatographic interferences from the tablet excipients were found. The suitability of these methods for the quantitative determination of the compounds was proved by validation.