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International Journal of Analytical Chemistry
Volume 2009, Article ID 237601, 8 pages
Research Article

Simple Spectrophotometric Method for Determination of Paroxetine in Tablets Using 1,2-Naphthoquinone-4-Sulphonate as a Chromogenic Reagent

Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia

Received 13 October 2008; Accepted 10 February 2009

Academic Editor: Maria Augusta Raggi

Copyright © 2009 Ibrahim A. Darwish et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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 ( 𝜆 m a x ) 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  𝜇 g m L − 1 . The regression equation for the calibration data was: A = 0.0031 + 0.1609 C, with good correlation coefficients (0.9992). The molar absorptivity ( 𝜀 ) was 5 . 9 × 1 0 5 L  m o l − 1 1  c m − 1 . The limits of detection and quantitation were 0.3 and 0.8  𝜇 g m L − 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 9 7 . 1 7 ± 1 . 0 6 %. The results obtained by the proposed method were comparable with those obtained by the official method.