Hayashi Tomohisa, Sakurada Ikuo, Honda Kensuke, Motohashi Shigeyasu, Uchikura Kazuo
School of Pharmacy, Nihon University, 7-7-1 Narashinodai, Funabashi, Chiba 274–8555, Japan.
Anal Sci. 2012;28(2):127-33. doi: 10.2116/analsci.28.127.
Electrochemical detection of sugar-related compounds was conducted using a boron-doped diamond (BDD) electrode as a detector for flow-injection analysis (FIA). Sugar-related compounds oxidize at high applied potentials, for which the BDD electrode is suitable for electrochemical measurements. Conditions for an FIA system with a BDD detector were optimized, and the following detection limits were achieved for sugar-related compounds: monosaccharides, 25-100 pmol; sugar alcohols, 10 pmol; and oligosaccharides, 10 pmol. The detection limit for monosaccharide D-glucose (Glu) was 105 pmol (S/N = 3). A linear range was acquired from the detection limit to 50 nmol, and the relative standard deviation was 0.65% (20 nmol, n = 6). A high-performance liquid chromatography (HPLC) column was added to the system between the sample injector and the detector and detection limits to the picomole level were achieved, which is the same for the HPLC system and the FIA system. The electrochemical oxidation reaction of Glu was examined using cyclic voltammetry with the BDD detector. The reaction proved to be irreversible, and proceeded according to the following two-step mechanism: (1) application of a high potential (2.00 V vs. Ag/AgCl) to the electrode causes water to electrolyze on the electrode surface with the simultaneous generation of a hydroxyl radical on the surface, and (2) the hydroxyl radical indirectly oxidizes Glu. Thus, Glu can be detected by an increase in the oxidation current caused by reactions with hydroxy radicals.
采用硼掺杂金刚石（BDD）电极作为流动注射分析（FIA）的检测器，对糖类相关化合物进行电化学检测。糖类相关化合物在高外加电位下会发生氧化反应，而BDD电极适用于此类电化学测量。对带有BDD检测器的FIA系统的条件进行了优化，糖类相关化合物的检测限如下：单糖为25 - 100皮摩尔；糖醇为10皮摩尔；寡糖为10皮摩尔。单糖D - 葡萄糖（Glu）的检测限为105皮摩尔（信噪比 = 3）。检测限到50纳摩尔之间获得了线性范围，相对标准偏差为0.65%（20纳摩尔，n = 6）。在系统的进样器和检测器之间添加了一根高效液相色谱（HPLC）柱，实现了皮摩尔级别的检测限，这对于HPLC系统和FIA系统是相同的。使用带有BDD检测器的循环伏安法研究了Glu的电化学氧化反应。该反应被证明是不可逆的，并且按照以下两步机制进行：（1）在电极上施加高电位（相对于Ag/AgCl为2.00 V）会使电极表面的水电解，同时在表面生成羟基自由基，以及（2）羟基自由基间接氧化Glu。因此，可以通过与羟基自由基反应引起的氧化电流增加来检测Glu。
