Kinetic methods for accurate determination of nortriptyline hydrochloride have been described. The methods are based on the oxidation of nortriptyline hydrochloride with KMnO4 in acidic and basic media. In acidic medium, the decrease in absorbance at 525.5 nm and in basic medium, the increase in absorbance at 608.5 nm were measured as a function of time. The variables affecting the reactions were carefully investigated and optimised. Kinetic models such as initial rate, rate constant, variable time and fixed time were employed to construct the calibration curves. The initial rate and fixed time methods were selected for quantification of nortriptyline hydrochloride. In acidic medium, the calibration curves showed a linear response over the concentration range 10-50 μg mL(-1) for initial rate and 10-60 μg mL(-1) for fixed time method (2 min). In basic medium, the calibration graphs were linear over the concentration range 10-100 μg mL(-1) for initial rate and fixed time methods (4 min). In acidic medium, the limits of detection for initial rate and fixed time methods (2 min) were 1.02 and 3.26 μg mL(-1), respectively. In basic medium, the limits of detection were found to be 1.67 and 1.55 μg mL(-1) for initial rate and fixed time methods (4 min), respectively. The initial rate and fixed time methods have been successfully applied to the determination of nortriptyline hydrochloride in commercial dosage form. Statistical comparison of the results of the proposed methods with those of reference method exhibited excellent agreement and there is no significant difference between the compared methods in terms of accuracy and precision.
