The voltammetric study and determination of ramipril in dosage forms and biological fluids

The voltammetric behavior of ramipril was studied using cyclic voltammetry, direct current polarography (DCt), differential pulse polarography (DPP) and alternating current polarography (ACt). Ramipril developed well-defined cathodic waves in Britton-Robinson buffers over the pH range 6-12. The waves were characterized as being diffusion-controlled, irreversible and partially affected by adsorption phenomenon. The diffusion-current constant (Id) was 1.24 +/- 0.02. The current-concentration plots were rectilinear over the range 10-50, 4-40 and 0.16-12 micrograms/ml in the DCt, DPP and ACt modes, respectively, with a minimum detectability (S/N = 2) of 0.02 microgram/ml (4.8 x 10(-8) M) using the latter mode. The proposed method was successfully applied to the determination of ramipril in commercial tablets. Hydrochlorothiazide, which is frequently co-formulated with ramipril, did not interfere with the assay. Furthermore, the proposed method was applied to the determination of ramipril in urine and plasma adopting the ACt technique. The percentage recoveries were 97.12 +/- 0.56 and 94.97 +/- 0.62%, respectively. A pathway for the electrode reaction was proposed.