杨梅素在液体石蜡-石墨电极上的电化学反应机理

以液体石蜡-石墨电极作为工作电极,获得了杨梅素的循环伏安图.杨梅素在0.1mol/L KCl的BR缓冲溶液中(pH=2.01),以Ag-AgCl为参比电极,于0.435,0.853V处产生两个灵敏的氧化峰,其中0.435V为主氧化峰.在此基础之上,研究了杨梅素在液体石蜡-石墨电极上的反应机理,提出由于包裹在石墨颗粒上的液体石蜡阻止了杨梅素B环氧化过程中第二个电子转移,其在碳糊电极上的主氧化峰可能是一个有自由基参与、受吸附控制的可逆过程.具体过程为,首先杨梅素被氧化为半醌自由基,之后C环上3位羟基通过歧化反应,直接失去一个电子被氧化成对醌化合物,而非邻醌.

Electrochemical reaction mechanism of myricetin on paraffin-graphite powder electrode

An electrochemical investigation of myricetin oxidation on a paraffin-graphite powder electrode was carried out using cyclic voltammetry over a wide pH interval.In the BR KCl buffer(pH=2.01),0.1 mol/L myricetin can be sensitively detected,and two main oxidation peaks occur at 0.435 and 0.853 V(Ag-AgCl as reference electrode).Myricetin adsorbs strongly on the electrode surface and the oxidation is pH dependent.As paraffin can form compact hydrophobic films on graphite powder,it inhibits the oxidation of myricetin by selectively blocking the second electron transfer of the B ring,and yields the semiquinone radical as main product,so the reaction myricetin to semiquinone radical nearly achieves reversibility.The 3-hydroxy group on the C ring is then oxidized as a result of semiquinone disproportionation directly to a quinoid(quinone methide) product,rather than to an o-quinone.