RAPID-SCANNING VOLTAMMETRIC DETECTION IN FLOWING STREAMS

`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 mu m 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.