A simple, rapid, sensitive and accurate spectrophotometric method for the determination of captopril in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with captopril in the presence of neocuproine (NC) (2,9-dimethyl-1,10-phenanthroline) reagent in acetate buffer at pH 5.0. Copper(II) is reduced easily by captopril to Cu(I)–neocuproine complex, which shows an absorption maximum at 448nm. Beer’s law was obeyed in the concentration range 0.3–3.0μgmL−1 with a minimum detection limit (LOD) of 0.039μgmL−1 and a quantification limit (LOQ) of 0.129μgmL−1. For more accurate results, Ringbom optimum concentration ranges was 0.5–2.7μgmL−1. The apparent molar absorbtivity and Sandell sensitivity were calculated. The validity of the proposed method was tested by analyzing the pure and pharmaceutical formulations and compared well with those obtained by the official method and demonstrated good accuracy and precision.
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