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 microeiectrode 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^-8M, and the response shows good linearity over the concentration range 10^-3-10^-8M 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, halfwave potential, and reversibility. The utility of this system is demonstrated by the detection of uric acid and ascorbic acid in blood and urine.