Rapid scanning voltammetric detection in flowing streams

Abstract

The technique of rapid scanning amperometric detection is described. This method combines an ability to perform rapid potential scanning of the analyte, which facilitates the construction of a three-dimensional current trace at different potentials versus time, with the technique of pulsed amperometric detection, which allows the application of cleaning/activation pulses to the detection electrode. Unlike pulsed voltammetry with scanning voltammetric detection, which is described by other workers, this method employs a true microelectrode as the detector (an array of eight 5 µm band electrodes). Rapid scanning and pulsing is possible without interference from non-faradaic charging currents that may mask the faradaic signals. Catecholamine separation by high-performance liquid chromatography was selected as a model system to demonstrate the detection method in flowing streams. Measurements were made using a series of different pulsing rates; no distortion of the voltammetric signal was observed up to a pulsing rate of 20 ms, 50 Hz (effective scan rate, 4.4 V s^–1). Comparison with a series of d. c. amperometric measurements at a set of different potentials demonstrates the scope of analyte information that this technique makes available. Analyte data can be obtained in both electrochemical and chromatographic domains.