ADSORPTIVE VOLTAMMETRIC BEHAVIOR OF OMEPRAZOLE AND ITS APPLICATION / 药学学报

ABSTRACT

AIM　To study the electrochemical behavior of omeprazole (OPZ) and a new method for the determination of the compound was established by adsorptive stripping voltammetry. METHODS　Linear-sweep polarography and cyclic voltammetry were used. RESULTS　In a supporting electrolyte containing 0.1 mol*L-1 NH3-NH4Cl, a reduction peak of OPZ was observed by linear-sweep voltammetry at Hg electrode. The peak showed a potential of -1.04 V (vs Ag/AgCl at 100 mV*s-1) and adsorptive characteristics. The adsorbed species is most probably the neutral molecular of OPZ. The saturated adsorption of OPZ at Hg electrode is 9.55×10-11 mol*cm-2 and every OPZ molecule occupies an area of 1.74 nm2. On the surface of the hanging mercury drop electrode, the adsorption of OPZ obeys Frumkin adsorption isotherm. The adsorption coefficient β is 1.32×106, the Gibbs energy of adsorption ΔGθ is -34.93 kJ*mol-1, the number of electrons transferred n is 4, the kinetics parameter αnα is 0.78, the rate constant of the surface electrode reaction ks is 0.18 s-1, the diffusion coefficient D of OPZ in solution is 1.03×10-5 cm2*s-1. The detection limit of the adsorptive stripping voltammetry of OPZ is 2.0×10-9 mol*L-1 under optimized condition. CONCLUSION　This indicates an irreversible process with adsorption.