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Stability constants and voltammetric determination of ramipril in tablet and real urine samples

O.A.Farghaly, N.A.Mohamed, A.A.Gahlan, M.A.El-Mottaleb

Fivemetal ions viz; Fe(III),Al(III), Cr(III), La(III),Y(III) were selected to elucidate the interaction of these metal ions with ramipril (RMP) using potentiometric method. The protonation constant of the ligand and stability constants of complexes formed have been tabulated at ionic strength I=0.05MNaNO3 in aqueous solutions at 250C±0.1. Complexes of 1:1, 1:2 and/or 1:3 metal to ligand ratios are formed depending on the nature of the ligand or metal ions. The order of stability constants of the binary complexes was examined. Different parameters such asmedium, pH, accumulation potential, scan rate, accumulation time and ionic strengthwere tested as optimal to optimize the conditions for the determination of RMP by square wave cathodic stripping voltammetry method. The adsorbed form is reduced irreversible using 0.6MBritton-Robinson buffer (pH9.0). Linear concentration ranges from0.083 to 0.417ng/mL at accumulation times 15, 30 and 60 s, respectively, could be determined successfully. The standard addition method was used to determine RMP in pure solutions, tablets and in biological fluids with satisfactory results. The data obtained are compared with standard official method.