Fabrication and performance of a three‐dimensionally adjustable device for the amperometric detection of microchip capillary electrophoresis

A microchip CE‐amperometric detection (AD) system has been fabricated by integrating a two‐dimensionally adjustable CE microchip and an AD cell containing a one‐dimensionally adjustable disk detection electrode in a Plexiglas holder. It facilitates the precise 3‐D alignment between the channel outlet and the detection electrode without a complicated 3‐D manipulator. The performance of this unique system was demonstrated by separating five aromatic amines (1,4‐phenyldiamine, aniline, 2‐methylaniline, 4‐chloroaniline, and 1‐naphthylamine) of environmental concern. Factors influencing their separation and detection processes were examined and optimized. The five analytes have been well separated within 140 s in a 74 cm long separation channel at a separation voltage of +2500 V using a 10 mM phosphate buffer (pH 3.5). Highly linear response is obtained for the five analytes over the range 20–200 μM with the detection limits ranging from 0.46 to 1.44 μM, respectively. The present system demonstrated long‐term stability and reproducibility with RSDs of less than 5% for the peak current (n = 9). The new approach for the microchannel‐electrode alignment should find a wide range of applications in CE, flowing injection analysis, and other microfluidic analysis systems.

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