Eco-friendly spectrophotometric determination of moxifloxacin in pharmaceutical dosage form via ion-pair complexation with erythrosine B

Abstract A rapid, sensitive, and eco-friendly spectrophotometric method was developed for the quantitative determination of moxifloxacin (MOX) based on ion-pair formation with erythrosine B (EB). The resulting pink-colored ion pair complex exhibited a maximum absorbance at 554 nm. Systematic optimization of reaction parameters, including buffer pH, dye concentration, and diluent selection, ensured maximum sensitivity and reproducibility. The method demonstrated excellent linearity within the concentration range of 0.2–1.2 µg mL − 1 ( r = 0.9990), with low detection and quantification limits (LOD = 0.05 µg mL − 1 , LOQ = 0.15 µg mL − 1 ). The calculated molar absorptivity (3.41 × 10⁵ L·mol⁻¹·cm⁻¹) and Sandell’s sensitivity (1.18 × 10⁻³ µg·cm⁻² per 0.001 absorbance unit) confirmed the high analytical sensitivity of the proposed method. Validation in accordance with ICH guidelines demonstrated excellent accuracy (mean recoveries of 99.43–99.77%), precision (RSD < 1.7%), and robustness against minor variations in experimental conditions. Application of the proposed method to commercial eye-drop formulation produced recoveries ranging from 99.1% to 100.46%. Statistical comparison with reference method revealed no significant differences ( t- value = 1.008, F- value = 1.124). These findings establish the proposed assay as equivalent in accuracy and precision to established techniques, while offering practical simplicity, cost-effectiveness, and environmental compatibility. By eliminating organic solvents and minimizing reagent consumption, the method aligns with green chemistry principles and provides a practical, sustainable tool for routine pharmaceutical quality control.