Green stability-indicating capillary electrophoretic method for simultaneous determination of Lesinurad and Allopurinol in tablet dosage form: Degradation kinetics investigation

Abstract

A binary mixture of Lesinurad (LES) and Allopurinol (ALP) is a newly marketed anti-gout combination where no stability indicating methods have been reported for its analysis. In this work, a simple, green stability indicating capillary zone electrophoretic method coupled with a diode array detector (CZE-DAD) has developed and validated for analyzing this mixture in their combined dosage form. Separation was achieved using fused silica capillary (55 cm × 50 μm id) using 50 mM borate buffer adjusted to pH 10 with 0.5 M NaOH. The linearity concentration ranges were 5–50 and 10–100 μg/mL for LES and ALP, respectively. The stability indicating ability of the proposed method was investigated by analyzing the two drugs after being subjected to several stress conditions as per ICH guidelines. The developed method was able to separate the two intact drugs from their degradation products formed under different stress conditions (acidic, basic, oxidation). In addition, the developed method has been applied to investigate the degradation kinetics of LES and ALP under acidic, basic and oxidative conditions. The degradation of the two drugs was found to follow pseudo-first order kinetics and degradation half-lives were also calculated for both drugs under different stress conditions. The developed CZE method is the first in the literature for determination of both LES and ALP in the presence of their related degradation products with high separation efficiency, minimum solvent consumption, enhanced method greenness and low operation cost. Thus, the proposed method is an efficient simple eco- friendly analytical tool for the routine analysis of LES and ALP in their combined dosage form in presence of their degradation products in quality control laboratories.