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 x 10(-11) mol.cm-2 and every OPZ molecule occupies and 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 beta is 1.32 x 10(6), the Gibbs energy of adsorption delta G theta is -34.93 kJ.mol-1, the number of electrons transferred n is 4, the kinetics parameter alpha n alpha 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 x 10(-5) cm2.s-1. The detection limit of the adsorptive stripping voltammetry of OPZ is 2.0 x 10(-9) mol.L-1 under optimized condition.
Conclusion: This indicates an irreversible process with adsorption.