Development and validation of a hydrotropic UV–Visible spectrophotometric method for the simultaneous assay of ornidazole and ofloxacin tablets

Abstract

Introduction

In the Democratic Republic of Congo (DRC), weaknesses in pharmaceutical distribution systems contribute to the circulation of substandard and falsified medicines. The fixed-dose combination of ofloxacin and ornidazole is commonly prescribed for the treatment of mixed bacterial and protozoal infections; however, it lacks harmonized monographs in major international pharmacopoeias (USP, BP, and EP).

Purpose

This study aimed to develop and validate an alternative, environmentally friendly analytical method for the simultaneous determination of ofloxacin and ornidazole using UV–Visible spectrophotometry.

Methods

Solubilization was achieved using an effective ternary mixture (10% urea/10% nicotinamide, w/v), alkalinized to pH 9.5 with NaOH and measured using a calibrated digital pH meter. This alkaline condition exploits the amphoteric nature of ofloxacin by inducing a bathochromic shift to 330 nm. Quantification was based on Vierordt’s simultaneous equation spectrophotometric method. Validation was conducted in accordance with ICH Q2(R2) guidelines using a Total Error approach (accuracy profile) over a range of 80% to 120% of target concentrations.

Results

The method demonstrated specificity in the presence of common excipients. Metrological performance showed excellent linearity (R² = 0.9923 for ornidazole and R² = 0.9913 for ofloxacin), supported by 45 experimental observations and mean recovery rates of 99.61% and 99.95%, respectively. The lower limit of quantification (LLOQ) was graphically established from the accuracy profile at 8.6000 µg/mL and 3.4000 µg/mL, ensuring 95% decisional reliability. Expanded uncertainty (k = 2, 95% CI) remained within acceptable limits (3.68% and 3.50%). Assay of a commercial batch confirmed compliance with pharmacopoeial specifications.

Conclusion

The validated method provides a cost-effective alternative for routine quality control laboratories. By using an aqueous hydrotropic system instead of hazardous organic solvents, this protocol offers a robust and sustainable screening tool for market surveillance in resource-limited settings while significantly reducing the laboratory’s environmental footprint.