Innovative Dual-Technique Approach to Levofloxacin Assay: Spectrophotometric Chelation and Microfluidic Paper-Based System for Enhanced Pharmaceutical Quality Control

This study introduces a dual-technique strategy for levofloxacin quantification, combining ultraviolet-visible spectrophotometry and a microfluidic paper-based analytical device (µPAD) to address the need for cost-effective, precise pharmaceutical quality control. Leveraging the reaction between levofloxacin and chlorophenol red, both methods form a colored complex (λ_max = 574 nm) via an acid-base interaction stabilized by electrostatic and hydrogen bonding. The spectrophotometric method demonstrates high sensitivity (limit of detection (LOD): 2.50 µg/mL, linear range: 5–100 µg/mL) with robust intra-day (relative standard deviation (RSD): 0.946–1.730%) and inter-day precision (RSD: 1.401–2.198%), alongside recovery rates of 91.5–102.6%. In contrast, the µPAD offers portability and rapid analysis (LOD: 10.119 µg/mL, linear range: 100–1000 µg/mL), achieving comparable accuracy (recovery: 90.6–96.1%) with minimal reagent consumption. Both techniques were validated according to the International Council for Harmonization guidelines, exhibiting negligible matrix interference in commercial formulations (Levolen, Levobact, Levofloxacin Vitapure). The spectrophotometric method excels in laboratory settings for precision, while the µPAD enables on-site testing, aligning with green chemistry principles. This dual approach bridges technological gaps, providing versatile tools to ensure accurate dosing, support antimicrobial stewardship, and enhance global pharmaceutical quality control.