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

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.

Adsorptive Voltammetric Behavior of Riboflavine Tetrabut yrate and Its Measurement of Rate Constant at the Mercury Electrode / 分析化学

Cyclic voltammetry shows that, in a supporting ele ctrolyte of NaOH,riboflavine tetrabutyrate（RT）has a pair of cathodic and anodi c peaks at Hg electrode. The peak potentials Epc=Epa=-0.64　 V（vs.Ag/Agcl）.　The adsorptive characteristics of RT are explored in detai ls with various methods.　The adsorbed species is most probably neutral molecule of RT.The saturated adsorption amount of RT at Hg electrode is 5.42×10-11 　mol/cm2 and every RT molecule occupied 3.06　nm2. On the surface of HMDE ，the adsorption of RT obeys Frumkin dasorption isotherm. The adsorptive coeffic ient β，the attractive factor γ are 4.60×105，1.10 and the adsorption free energy ΔG, is　－32.30　kJ/mol, respectively. The electrode proc ess kinetic behavior has also been studied by using cyclic voltammetry. Under th e experimental conditions the rate constants for electron transfer are determine d. The values of ks are in good agreement with literature′s results.