Spectrophotometric Quantification of Atomoxetine Hydrochloride Based on Nucleophilic Substitution Reaction with 1,2-Naphthoquinone-4-Sulfonic Acid Sodium Salt (NQS)

Objectives: A simple, sensitive, selective, and cost-effective colorimetric method has been established for the quantitative estimation of atomoxetine hydrochloride in bulk and formulation. Materials and Methods: It was established based on the visible reaction between atomoxetine hydrochloride and 1,2-naphthoquinone-4-sulfonic acid sodium salt in a basic medium (potassium hydroxide). The resulting orange colored chromogen exhibited an absorption maximum at 474 nm. Results: Based on the optimization studies, distilled water as the solvent, 1% w/v potassium hydroxide (2 mL), and 0.3% w/v 1,2-naphthoquinone4-sulfonic acid sodium salt (2 mL) were used in the method. The developed method was validated per the International Council for Harmonization (ICH) guidelines. The linearity was found at a concentration of 10-50 mu g/mL. The method showed a good correlation between the concentration of atomoxetine hydrochloride and its absorbance. The correlation coefficient (r2 ) of 0.999 evidenced the same. The limits of detection and quantification were 0.20 and 0.606 mu g/mL, respectively, for atomoxetine hydrochloride. The accuracy and precision of the method were also evaluated and the results obtained were within the acceptance criteria (relative standard deviation % < 2.00). The percentage assay of atomoxetine hydrochloride proved to be 101.52, which is in accordance with its label claim. Conclusion: The developed method is non-complex and can be effectively employed in the analytical practices of atomoxetine hydrochloride in pharmaceutical dosage forms.