Cvacka Josef, Quaiserová Veronika, Park JinWoo, Show Yoshiyuki, Muck Alexander, Swain Greg M
Department of Chemistry, 320 Chemistry Building, Michigan State University, East Lansing, Michigan 48824-1322, USA.
Anal Chem. 2003 Jun 1;75(11):2678-87. doi: 10.1021/ac030024z.
The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. The microelectrodes were prepared by coating thin films of polycrystalline diamond on electrochemically sharpened platinum wires (76-, 25-, and 10-microm diameter), using microwave-assisted chemical vapor deposition (CVD). The diamond-coated wires were attached to copper wires (current collectors), and several methods were explored to insulate the cylindrical portion of the electrode: nail polish, epoxy, polyimide, and polypropylene coatings. The microelectrodes were characterized by scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for Ru(NH3)6(3+/2+) and Fe(CN)6(3-/4-) at low scan rates. The microelectrodes formed with the large diameter Pt and sealed in polypropylene pipet tips were employed for end-column detection in CE. Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM phosphate buffer, pH 6.0, run buffer, and a 30-cm-long fused-silica capillary (75-microm i.d.) with dopamine, catechol, and ascorbic acid serving as test analytes. The background current (approximately 100 pA) and noise (approximately 3 pA) were measured at different detection potentials and found to be very stable with time. Reproducible separation (elution time) and detection (peak current or area) of dopamine, catechol, and ascorbic acid were observed with response precisions of 4.1% or less. Calibration curves constructed from the peak area were linear over 4 orders of magnitude, up to a concentration between 0.1 and 1 mM. Mass limits of detection for dopamine and catechol were 1.7 and 2.6 fmol, respectively (S/N = 3). The separation efficiency was approximately 33,000, 56,000, and 98,000 plates/m for dopamine, catechol, and ascorbic acid, respectively. In addition, the separation and detection of 1- and 2-naphthol in 160 mM borate buffer, pH 9.2, was investigated. Separation of these two analytes was achieved with efficiencies of 118,000 and 126,000 plates/m, respectively.
本文讨论了用于毛细管电泳电化学检测（CE - EC）的硼掺杂金刚石微电极的制备及其特性。这些微电极是通过微波辅助化学气相沉积（CVD），在电化学锐化的铂丝（直径分别为76、25和10微米）上涂覆多晶金刚石薄膜制成的。将涂有金刚石的导线连接到铜丝（集电器）上，并探索了几种方法来绝缘电极的圆柱形部分：指甲油、环氧树脂、聚酰亚胺和聚丙烯涂层。通过扫描电子显微镜、拉曼光谱和循环伏安法对微电极进行了表征。在低扫描速率下，它们表现出低且稳定的背景电流，以及对于Ru(NH3)6(3+/2+)和Fe(CN)6(3-/4-)呈S形的伏安曲线。用大直径铂制成并密封在聚丙烯移液管尖端的微电极用于CE中的柱端检测。使用10 mM磷酸盐缓冲液（pH 6.0）作为运行缓冲液，以及一根30厘米长的熔融石英毛细管（内径75微米），以多巴胺、儿茶酚和抗坏血酸作为测试分析物，对CE - EC系统和电极性能进行了评估。在不同检测电位下测量了背景电流（约100 pA）和噪声（约3 pA），发现它们随时间非常稳定。观察到多巴胺、儿茶酚和抗坏血酸具有可重现的分离（洗脱时间）和检测（峰电流或峰面积），响应精密度在4.1%或更低。由峰面积构建的校准曲线在4个数量级内呈线性，最高浓度可达0.1至1 mM。多巴胺和儿茶酚的质量检测限分别为1.7和2.6 fmol（S/N = 3）。多巴胺、儿茶酚和抗坏血酸的分离效率分别约为33,000、56,000和98,000理论塔板数/米。此外，还研究了在160 mM硼酸盐缓冲液（pH 9.2）中1 - 和2 - 萘酚的分离与检测。这两种分析物的分离效率分别为118,000和126,000理论塔板数/米。
