Spectrophotometric methods for the determination of ampicillin by potassium permanganate and 1-chloro-2,4-dinitrobenzene in pharmaceutical preparations

Two simple and sensitive kinetic methods for the determination of ampicillin (AMP) are described. The first method is based on kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 25 min. The absorbance of the colored manganate ions is measured at 610 nm. The second method is based on the reaction of AMP with 1-chloro-2,4-dinitrobenzene (CDNB) in the presence of 0.1 mol L−1 sodium bicarbonate. Spectrophotometric measurement was achieved by recording the absorbance at 490 nm for a fixed time of 60 min. All variables affecting the development of the color were investigated and the conditions were optimized. Plots of absorbance against concentration in both procedures were rectilinear over the ranges 5–30 and 50–260 μg mL−1, with mean recoveries 99.80 and 99.91, respectively. The proposed methods were successfully applied for the determination of AMP in bulk powder and in capsule dosage form. The determination of AMP by the fixed concentration method is feasible with the calibration equations obtained, but the fixed time method proves to be more applicable.