MULTICHANNEL ELECTROCHEMICAL DETECTION WITH A MICROELECTRODE ARRAY IN FLOWING STREAMS

A multichannel electrochemical detection system for flow injection analysis (FIA) and high-performance liquid chromatography (HPLC) has been fabricated using a 16-channel microelectrode array. The 16-channel detection was performed by collecting current responses at 16 microband electrodes held at potentials differed stepwise by means of a multipotentiostat to show three-dimensional results, i.e., time, current, and potential. The detection limit for the ferrocene derivative is 10(-8) M, and the response shows good linearity over the concentration range 10(-3)-10(-8) M at 16-channel detection. The 80-channel detection was also carried out by applying a 5-step potential staircase of 10-mV step height to the 16 individual electrodes. The faradaic current in each potential step was sampled in the time region where the charging current decreased negligibly. A hydrodynamic voltammogram comprising 80 data points can be obtained in 0.26 s. This rapid detection system was applied to FIA and HPLC of a mixture of several electroactive chemicals, such as ferrocene derivatives, ascorbic acid, uric acid, and catecholamines. These hydrodynamic voltammograms provide useful electrochemical information, i.e., concentration, half-wave potential, and reversibility. The utility of this system is demonstrated by the detection of uric acid and ascorbic acid in blood and urine.