Metal complexes and voltammetric determination of enalapril in tablet and urine samples

Author(s): O.A.Farghaly*, N.A.Mohamed, O.A.Hazzazi, A.A.Gahlan, M.A.Mottaleb

Twelvemetal ions viz; Fe(III),Al(III), Cr(III), La(III),Y(III), Bi(III), Cu(II), Co(II),Ni(II),Mn(II), Pd(II) andHg(II)were selected to elucidate their interaction with enalapril maleate using potentiometric method. The protonation constant of the ligand and stability constants of complexes formed have been tabulated using three ionic strengths, I = 0.05, 0.1and 0.15 M NaNO3 in aqueous solutions at 25 ± 0.10C. 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. The voltammetric behavior of enalaprilwas studied using square wave cathodic stripping voltammetric method at carbon paste electrode (CPE) in pharmaceutical dosage forms (tablet) and in biological fluids (spiked and real urine sample) has been developed and evaluated. Different parameters such asmedium, pH, accumulation potential, scan rate, accumulation time and ionic strength were tested to optimum condition to optimize the conditions for the determination of Enalapril. The adsorbed form is reduced irreversible at optimal conditions viz; 0.04MBritton-Robinson buffers (pH9.00). Linear concentration ranges 0.985-24.62 ng/mLat 15s, 0.985- 14.77 at 30 s ng/mL and from0.985 - 4.925 at 60 s ng/mL, can be determined successfully. The standard additionmethodwas used to determine Lisinopril in pure solutions, tablets and in biological fluids with satisfactory results. The data obtained are compared with standard official method

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