Spectrophotometric study for the reaction between fluvoxamine and 1,2-naphthoquinone-4-sulphonate: Kinetic, mechanism and use for determination of fluvoxamine in its dosage forms

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak (λmax) at 470 nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65 kcal mol−1. Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with FXM concentration (C) was obeyed in the range of 0.6–8 μg ml−1. The regression equation for the calibration data was A = 0.0086 + 0.1348C, with good correlation coefficient (0.9996). The molar absorptivity (ɛ) was 5.9 × 104 l mol−1 cm−1. The limits of detection and quantification were 0.2 and 0.6 μg 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 FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47 ± 0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM.