Volk K J, Yost R A, Brajter-Toth A
Anal Chem. 1989 Aug 1;61(15):1709-17. doi: 10.1021/ac00190a024.
The electrochemical oxidation pathway of uric acid was determined by on-line electrochemistry/thermospray/tandem mass spectrometry. Intermediates and products formed as a result of electrooxidation were monitored as the electrode potential was varied. Several reaction intermediates have been identified and characterized by tandem mass spectrometry. The tandem mass spectrometric results provide convincing evidence that the primary intermediate produced during the electrooxidation of uric acid has a quinonoid diimine structure. The results indicate that once formed via electrooxidation, the primary intermediate can follow three distinct reaction pathways to produce the identified final products. The final electrochemical oxidation products observed in these studies were urea, CO2, alloxan, alloxan monohydrate, allantoin, 5-hydroxyhydantoin-5-carboxamide, and parabanic acid. The solution reactions that follow the initial electron transfer at the electrode are affected by the vaporizer tip temperature of the thermospray probe. In particular, it was found that at different tip temperatures either hydrolysis or ammonolysis reactions of the initial electrochemical oxidation products can occur. Most importantly, the results show that the on-line combination of electrochemistry with thermospray/tandem mass spectrometry provides otherwise difficult to obtain information about redox and associated chemical reactions of biological molecules such as the structure of reaction intermediates and products, as well as providing insight into reaction pathways.
尿酸的电化学氧化途径通过在线电化学/热喷雾/串联质谱法测定。随着电极电位的变化，监测电氧化形成的中间体和产物。通过串联质谱法鉴定并表征了几种反应中间体。串联质谱结果提供了令人信服的证据，表明尿酸电氧化过程中产生的主要中间体具有醌二亚胺结构。结果表明，一旦通过电氧化形成，主要中间体可以遵循三种不同的反应途径生成已鉴定的最终产物。这些研究中观察到的最终电化学氧化产物是尿素、二氧化碳、尿囊素、尿囊素一水合物、尿囊酸、5-羟基乙内酰脲-5-甲酰胺和丙二酰脲。电极上初始电子转移后的溶液反应受热喷雾探头汽化器尖端温度的影响。特别是，发现在不同的尖端温度下，初始电化学氧化产物可能会发生水解或氨解反应。最重要的是，结果表明，电化学与热喷雾/串联质谱的在线结合提供了关于生物分子氧化还原及相关化学反应的难以获得的信息，如反应中间体和产物的结构，以及对反应途径的深入了解。
