Development of a spectroscopic approach for the estimation of glimepiride by oxidation reaction in an acidic environment and measurement of the area under the absorption curve using the UV-visible technique

Objective: This study aimed to develop and validate a simple spectrophotometric method for the determination of glimepiride (GLM) in pharmaceutical tablets, based on the formation of a colored complex with potassium permanganate in an acidic medium. Both direct absorbance measurement at the λmax of the complex and the Under Absorption Curve (UAC) approach were applied to enhance reliability and sensitivity Method: All experimental conditions were optimised to achieve the best analytical response. The area under the absorption curve (UAC) was measured for both the pure drug and the colourimetric reaction product as a supporting tool for quantitative estimation. Results: The method demonstrated good linearity across a range of concentrations with high precision from (0.5–15) µg/mL, linearity was (R2=0.997), low detection limits (LOD = 0.166) µg/mL, and scientifically acceptable recovery rates Rec % (101.291). The colourimetric reaction had a higher absorbance at λmax (400nm) and a significantly larger area under the absorption curve (UAC) of 33.656, confirming the occurrence of the chemical reaction and the formation of a coloured product responsible for the absorption. Conclusion: The proposed spectrophotometric method, using either direct absorbance at λmax or UAC determination, provides a precise, sensitive, and economical procedure suitable for routine quality control of GLM in pharmaceutical formulation.