Spectrophotometric determination of ampicillin and amoxicillin using tetracyanoethylene reagent in aqueous solution

Abstract

A simple, accurate and sensitive spectrophotometric method is described for the determination of ampicillin and amoxicillin in pure forms and in pharmaceutical formulations. The method is based on the reaction of these drugs in aqueous solution with tetracyanoethylene reagent in the presence of sodium hydroxide to produce a yellow coloured species measurable at λmax 322 and 325nm for ampicillin and amoxicillin respectively. The method has been used for the determination of 1.0-40 µg/ml for both drugs. The products have apparent molar absorptivies of 7.545×10³ and 9.915×10³ L.mol⁻¹.cm⁻¹ and Sandell sensitivities of 0.0532 and 0.042 µg.cm⁻² for above drugs respectively. Also, it was found that these products were formed in ratio of 1:1 species with stability constants of 7.96×10⁴ and 3.91×10⁴L/mol for ampicillin and amoxicillin respectively. The method was applied successfully to the assay of ampicillin and amoxicillin in their pharmaceutical formulations and was agreed well with its certified value and with the standard addition procedure.