Spectrophotometric determination of amoxicillin by reaction with N,N-dimethyl-p-phenylenediamine and potassium hexacyanoferrate(III)

A batch and flow injection analysis (FIA) spectrophotometric methods have been developed for the determination of amoxicillin (AMX) in aqueous solution and in pharmaceutical preparations. The methods are based on the reaction of AMX with N,N-dimethyl-p-phenylenediamine in the presence of potassium hexacyanoferrate(III) in alkaline medium. The water soluble blue colour product was measured at λmax 660 nm. Linearity was observed from 20 to 400 and 100 to 700 μg AMX in a final volume of 10 ml (i.e. 2-40 and 10-700 μg ml−1 AMX) with detection limits of 0.637 and 4.90 μg ml−1 AMX by batch and FIA procedure respectively. The effect of chemical and physical parameters have been carefully considered and the proposed procedures were successfully applied to the determination of AMX in pharmaceutical formulations.