The compact low-power-consumption instruments used in electrochemical (EC) detection make this method ideal for application to miniaturized analytical systems. As the technique is applicable to a wider range of substances than the fluorescence method, it is widely applied in liquid phase separation analysis systems on microfluidic platforms such as microchip capillary electrophoresis and liquid chromatography (LC). However, most of these microfluidic systems involve relatively high limits of detection (LODs) on the sub-μM to μM level, making them inapplicable to practical use as a result of significantly small current due to the small active area of microfabricated electrodes.  However, increasing the active area of band electrodes does not necessarily improve their sensitivity even though microelectrodes inherently have a high signal-to-noise (S/N) ratio. A typical EC flow cell is a microchannel with a band electrode placed orthogonally to the channel on the bottom wall. In such cells, the current rises gradually with longitudinal increase in the electrode area, while noise is proportional to the area. Thus, the S/N ratio decreases with the electrode area, leading to higher LODs that are commonly determined with a concentration providing a signal equivalent to S/N = 3. As a result, it is difficult to improve sensitivity either by increasing or decreasing the band electrode area. To address the issue, we developed a single comb-like electrode array featuring multiple narrow-band electrodes uniformly spaced and linked at each end. Work to incorporate the current electrode array into a miniaturized HPLC device is ongoing toward the creation of a high-performance analytical tool.

A single comb-like electrode array(WE) integrated in a microchip along with a column.

This work was partly supported by Grant-in-Aid for Scientific Research (C) (23550087) from Japan Society for the Promotion of Science.

 

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