中文摘要：

为研究儿茶素氧化的pH值效应,采用薄层长光程光谱电化学池,记录了儿茶素在pH值1.8～11.5的B-R缓冲介质中恒电势氧化过程的动态UV-Vis光谱,以及在碱性条件下自然氧化的动态光谱。结果表明,儿茶素的电氧化遵守随后聚合转化机理,pH值增大显著促进聚合反应而抑制电氧化步骤。pH值对儿茶素的氧化产物种类有决定性的复杂影响,在酸性条件下生成二聚体,在碱性条件下聚合大大增强,产物使溶液变黄色,可能为不同聚合度的低聚物。在碱性介质中自然氧化产物与相同pH值下的电氧化产物相同,但反应速率较慢,由氧气的溶入速率控制。

英文摘要：

The pH effect on the oxidation of (+)-catechin was investigated in B-R buffers at pH range from 1.8 to 11.5. Duringthe potentiostatic oxidation, the dynamic UV-Vis spectra were recorded in a long-optical-path thin-layer cell. The naturalchemical oxidation of (+)-catechin in alkaline media was also examined in the same cell for the purpose of comparison. The resultsshowed that the electro-oxidation of (+)-catechin abides by transformation polymerization mechanism, in which the followingpolymerization steps a...