Microbore HPLC is a very useful technique for analyzing small volume neurochemical extracts. Electrochemical detection, a staple of normal HPLC, has been difficult to implement in this restricted microbore environment. It is proposed to investigate tubular ultramicroband electrodes, <1 micrometer wide, for this application. These microelectrodes should give amperometric responses proportional to concentration and independent of flow rate over a wide range, and could be integrated into the column to avoid post-column dispersion of eluent components before detection. In addition, very fast dynamic voltammetry possible for microelectrodes will allow separation of overlapping eluent components with similar oxidation potentials, based on their differing electrokinetics. The microband electrodes are simple to fabricate from a variety of electrode materials and may be produced singly or in serial arrays with individual potential control. Phase I will seek to demonstrate one and two element microband electrodes, and to evaluate the geometric requirements for flow independent amperometric response toward model redox species and biogenic amines. Phase 11 will be used to develop further the electrode materials and fabrication technology for thin film multielement arrays, and to demonstrate and optimize prototype hardware in a microbore liquid chromatograph for enhanced separation of biogenic amines in clinical sample volumes.
