Validated spectrophotometric approach for the estimation of an antiepileptic drug: retigabine in pure form and pharmaceutical formulations utilizing N-Bromosuccinimide as an oxidant

A spectrophotometric method that is sensitive, easy, accurate, exact, reproducible, and verified has been developed for quantifying a new antiepileptic medication called retigabine in both its pure form and pharmaceutical formulations. The techniques employ N-bromosuccinimide (NBS) as an oxidizing agent and three dyes, namely amaranth, methylene blue, and indigo carmine. The three methods rely on the oxidation reaction of retigabine with an excess of N-bromosuccinimide (NBS) in an acidic environment. The unreacted NBS is then quantified by reacting it with fixed amounts of dyes, specifically amaranth, methylene blue, and indigo carmine. The absorbance at 520 nm, 664 nm, and 610 nm is measured for each respective dye. Linear relationships with high correlation coefficients (0.9992-0.9997) were observed under optimal conditions across concentration ranges of 0.5-12, 0.5-16, and 0.5–10 µg/ml. The limit of detection (LOD) for amaranth, methylene blue, and indigo carmine methods were determined to be 0.15, 0.15, and 0.14 µg/ml, respectively. The accuracy and precision of the approaches have been assessed for both intra-day and inter-day measurements. There was no observable interference caused by the typical tablet excipients. The proposed methodologies were verified in compliance with ICH recommendations and effectively utilized for the analysis of retigabine in pharmaceutical formulations. The reliability of the approaches was confirmed by conducting recovery studies employing the usual addition method. The findings produced by the proposed methods were statistically compared to those of the described approach using the student's t-test and F-test, which showed a significant level of agreement.