Spectrophotometric determination of benzyl penicillin in pharmaceutical preparations using copper(II) acetate as a complexing agent

Abstract

Copper(II) acetate is proposed as a chromogenic reagent for the spectrophotometric determination of benzyl penicillin. The reagent forms a green 2 : 1 complex with benzyl penicillin at pH 6–6.8. This complex is stable for nearly 25 min after its formation. The green species has an absorption maximum at 650 nm with a molar absorptivity of 0.24 × 10³ l mol^–1 cm^–1. Beer's law is valid over the concentration range 20–1000 µg ml^–1 of benzyl penicillin. The precision of the method is 1.89%. The reagent has been successfully used for the spectrophotometric determination of benzyl penicillin alone and in pharmaceutical preparations.