H2O2存在下橙皮苷的极谱催化波机理及其应用

目的　研究在过氧化氢存在下橙皮苷极谱催化波产生机理,建立测定橙皮苷的极谱催化波新方法。方法用线性变位极谱法、循环伏安法等技术。结果　橙皮苷C-4位上的羰基C==O首先经单电子单质子还原为自由基,产生第1个还原波;该自由基的一部分由于共轭作用使其能量降低,并进一步还原,产生第2个还原波,另一部分发生二聚化反应。当氧化剂H_{2O2 存在时,H2O2 氧化橙皮苷羰基还原中间体自由基,阻断了该自由基进一步还原和二聚化反应,并使橙皮苷再生,产生橙皮苷的极谱催化波。在0.12mol·L^-1 HAc-0.4 0mol·L^-1 NaAc (pH 5.3)1.0×10^-2mol·L^-1 H2O2 支持电解质中,该催化波的一阶导数峰电流与橙皮苷浓度在1.0×10^-7-1.8×10^-6 mol·L^-1 有良好线性关系,相关系数γ=0.9954。检测限为8.0×10^-8mol·L^-1 。结论　该催化波有较高的灵敏度,可用于药物分析。}

MECHANISM OF THE POLAROGRAPHIC CATALYTIC WAVE OF HESPERIDIN IN THE PRESENCE OF HYDROGEN PEROXIDE AND ITS APPLICATION

AIM To study the mechanism of a polarographic catalytic wave of hesperidin in the presence of hydrogen peroxide, and to propose a new catalytic wave method for the determination of hesperidin. METHODS Linear-potential scan polarography, cyclic voltammetry and DC polarography were used in this work. RESULTS In 0.12 mol·L^-1 HAc-0.40 mol·L^-1 NaAc (pH 5.3) supporting electrolyte, the carbonyl group C==O of hesperidin at the C-4 position yielded two reduction waves. The carbonyl group C==O firstly undergoes a 1 e, 1H⁺ reduction to form an intermediate free radical, producing the first reduction wave with peak potential -1.35 V (vs SCE). Further reduction of the radical was simultaneous with its dimerization. A part of the radical was further reduced, producing the second reduction wave with peak potential -1.70 V (vs SCE). Other part of the free radical was dimerized. The dimer could be oxidized at -1.17 V (vs SCE). When oxidant H_{2O2 was present, both the further reduction and dimerization were interrupted, and a polarographic catalytic wave was produced because H2O2 oxidized the intermediate free radical to regenerate the original C==O group. Based on the polarographic catalytic wave, a new method for the determination of hesperidin was proposed. 0.12 mol·L^-1 HAc-0.40 mol·L^-1 NaAc (pH 5.3)-1.0×10^-2 mol·L^-1 H2O2 solution was chosen as supporting electrolyte. The first-order derivative technique was used to eliminate the higher background current from H2O2 reduction and to well separate the catalytic wave from H2O2 reduction wave. The first-order derivative peak current of the catalytic wave is proportional to hesperidin concentration in the range of 1.0×10^-7 -1.8×10^-6 mol·L^-1 with correlation coefficient γ=0.9954. The limit of detection was 8.0×10^-8 mol·L^-1. The sensitivity of the catalytic wave was higher by one order of magnitude than other electrochemical methods based on reduction wave previously reported. CONCLUSION The catalytic wave method has higher sensitivity and can be used for pharmaceutical analysis.}