Spectrophotometric and atomic absorption spectrometric determination of ramipril and perindopril through ternary complex formation with eosin and Cu(II)

Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of ramipril and perindopril. Both methods are based on the formation of a ternary complex, extractable with chloroform, between copper(II), eosin and the two cited drugs. Spectrophotometrically under the optimum condition, the ternary complexes showed an absorption maximum at 535 nm, with apparent molar absorptivities of 6.55 and 4.00 x 10(3) mol(-1) x cm(-1) and Sandell's sensitivities of 5.80 x 10(-2) and 1.04 x 10(-1) microg x cm(-2) for perindopril and ramipril, respectively. The solution of ternary complex obeyed Beer's law in concentration ranges 10-60 and 20-100 microg x ml(-1) for perindopril and ramipril, respectively. The proposed method was applied to the determination of the two cited drugs in pharmaceutical tablets. The atomic absorption spectrometric method, directly through the quantitative determination of copper content of the organic extract of the complex, was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and perindopril dosage forms.