Simple spectrophotometric method for determination of paroxetine in tablets using 1,2-naphthoquinone-4-sulphonate as a chromogenic reagent.

Simple and rapid spectrophotometric method has been developed and validated for the determination of paroxetine (PRX) in tablets. The proposed method was based on nucleophilic substitution reaction of PRX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product of maximum absorption peak (lambda(max)) at 488 nm. The stoichiometry and kinetics of the reaction were studied, and the reaction mechanism was postulated. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with PRX concentration (C) was obeyed in the range of 1-8 mug mL(-1). The regression equation for the calibration data was: A = 0.0031 + 0.1609 C, with good correlation coefficients (0.9992). The molar absorptivity (epsilon) was 5.9 x 10(5) L mol(-1) 1 cm(-1). The limits of detection and quantitation were 0.3 and 0.8 mug mL(-1), respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of PRX in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 97.17 +/- 1.06 %. The results obtained by the proposed method were comparable with those obtained by the official method.