Application of microband array electrodes for end-column electrochemical detection in capillary electrophoresis

Abstract

Microfabricated arrays consisting of four individually addressable band electrodes have been used for end-column electrochemical detection in capillary electrophoresis (CE). The commercially available array was positioned 75–300 μm from the capillary outlet of a 75 μm i.d. capillary in the absence of an electrical-field decoupler. The detector performance was studied using non-aqueous CE and capillary flow injection analysis (CFIA) experiments on the basis of an acetonitrile/acetate buffer and ferrocene compounds as model substances. Redox cycling was demonstrated to yield a noticeable enhancement of the detector signal for an electrode-capillary end distance of 300 μm, particularly when the working electrode was surrounded by two electrodes regenerating the detected species. For an electrode-capillary end distance of 75 μm, a collection efficiency of 25% was obtained for generation-collection experiments at the inner neighbour band electrodes under CE and CFIA conditions. Different combinations of the individual band electrodes were exploited for dual-electrode detection in CE determinations of aromatic amines. An improvement of selectivity could be demonstrated for the separation of p-aminophenol and N-benzoyl-N-phenylhydroxylamine. Using a single microband of the array as the sensing electrode in CE measurements, the limits of detection for (ferrocenylmethyl)trimethylammonium perchlorate and ferrocene were found to be 1.6×10 −6 M and 1.5×10 −6 M, respectively.