INDIRECT SPECTROPHOTOMETRIC DETERMINATION OF AMOXICILLIN TRIHYDRATE IN PURE FORM AND IN PHARMACEUTICAL PREPARATIONS USING CRESOL RED DYE

Abstract: A rapid, sensitive, and indirect spectrophotometric method was developed for the determination of amoxicillin in pure form and in pharmaceutical preparations. The method is based on the oxidation of the pharmaceutical compound amoxicillin in an acidic medium (hydrochloric acid) with a known excess of the oxidizing agent N-bromosuccinimide (NBS); then the unreacted excess of the oxidizing agent leads to the paling of the color of the cresol red dye, which gives absorption at a wavelength of 442 nm. The method followed Beer’s law within a concentration range of 0.25-6.25 µg/ml and with a molar absorptivity of 3.72 × 104 Lꞏmol⁻¹ꞏcm⁻¹. The accuracy of the method reached 101.1%, and the precision of the method (relative standard deviation) was less than 1%. The limit of detection (LOD) value was 0.25 µg/ml, and the limit of quantitation (LOQ) value was 0.82 µg/ml. The method was successfully applied to pharmaceutical preparations of the pharmaceutical compound in the form of tablets and injections.