Fabrication, characterization, and application of a diamond microelectrode for electrochemical measurement of norepinephrine release from the sympathetic nervous system

The fabrication, electrochemical characterization and application of a boron-doped diamond microelectrode for the in vitro chronoamperometric measurement of the catecholamine neurotransmitter, norepinephrine (NE), are reported on. The microelectrode was formed by depositing a high quality, thin film of electrically conducting diamond on a sharpened 76 μm diam Pt wire. This new microelectrode, without any protective polymer coating, exhibited a sensitive and stable voltammetric response for NE released from sympathetic nerves innervating a mesenteric artery from a laboratory test animal. The background voltammetric current was low and stable over time and independent of the solution pH. The diamond microelectrode exhibited improved response performance over a conventional carbon fiber in this measurement. The superior performance is attributed to the non-polar, low-oxygen, sp3-bonded carbon surface on which weak adsorption of polar biomolecules (e.g., proteins) and other contaminants occurs. The microelectrode was also used in electrochemical detection, coupled with capillary zone electrophoresis, to analyze solutions for NE, other catecholamines and their major metabolites. In the amperometric detection mode, the microelectrode exhibited good response sensitivity, low mass limits of detection (100–400 amol, S / N ≥ 3) and excellent response reproducibility (RSD = 2–4%) without any conventional pretreatment.