A microfabricated flow-through cell with parallel-opposed electrodes for recycling amperometric detection

Flow-through recycling electrochemical detectors with dual Au electrodes were fabricated using micromachining techniques. Detector cells contained two microband electrodes that were 50 mu m wide by 3-5 mm long separated by a 5 or 10 mu m gap in a parallel-opposed configuration. One electrode was defined in the bottom of a channel which was etched into the surface of a Si wafer while the other electrode was defined on a glass substrate. The depth of the channel defined the gap distance between the electrodes. The Si and glass pieces were anodically bonded together to create a flow cell. The stability and reproducibility of single and dual electrode cells were characterized with cyclic voltammetry and amperometry during flow injection analysis (FIA). Single electrode detectors had detection limits of 50 nM with root mean square noise in the 3-10 pA range. The dual electrode cells showed enhanced sensitivity over single electrode cells through detection of analyte molecules multiple times as they were transported through the cell. Signal enhancements up to 60-fold were obtained with dual electrode cells during FIA at a flow rate of 50 nL/min. Simulations predict that signal-to-noise ratio enhancements > 100-fold may be possible with appropriate designs. (C) 1997 Elsevier Science S.A.