Multi-metric green-assessed validation of a chromogenic diazotization-coupling approach for the spectrophotometric determination of cephalexin

Cephalexin is a widely used cephalosporin antibiotic requiring a reliable and sustainable analytical method for its quantification in pharmaceutical matrices. Conventional techniques often involve complex procedures and hazardous solvents, highlighting the need for a simple, rapid, and green analytical approach. The proposed method is based on the diazotization of 2,4-dichloroaniline followed by coupling with cephalexin to produce a stable azo dye. Various experimental parameters were optimized to ensure maximum sensitivity, including reaction temperature, reaction time, reagent concentrations, and reagent volumes. The resulting product was analyzed via spectrophotometry at its maximum absorbance wavelength ( λ max ) of 430 nm. The method demonstrated a strong linear correlation ( r = 0.991) within the concentration range of 1–25 µg/mL, adhering to Beer’s law. The limit of detection and limit of quantification were determined to be 0.030 and 0.10 µg/mL, respectively. The technique showed excellent reproducibility with a relative standard deviation below 2% ( n = 8). Recovery rates ranged from 93.53% to 103.60% for pure cephalexin and 98.18% to 106.70% for dosage forms. The developed spectrophotometric method is highly reliable and free from interference by common pharmaceutical excipients. The environmental impact and practical utility of the proposed method were thoroughly validated through AGREE, eco-scale, and blue applicability grade index metrics, confirming their superior greenness and laboratory applicability compared to conventional techniques. Its greenness, simplicity, and accuracy make it a suitable approach for routine quality control analysis of cephalexin in clinical and industrial settings.