Dual electrode detection

Jorg, E. and Sontag, G. (1992). Determination of phenolic acids in honey by HPLC using coulometric dual electrode detection. Dtsch. Lebensm. Rundsh. 88,179-183. 

Dual-electrode detection for CE is much simpler to implement in the microchip format and offers additional sensitivity and selectivity due to the ability to monitor reversible redox reactions as well as help for identifying peaks in complex mixtures. Dual detection with serial gold [90,91] and carbon paste [92], fibre [93] and pyrolysed photoresist [94] working electrodes was reported. 

Design and application of liquid chromatography dual electrode detection... 

This review describes the design and application of liquid chromatography dual electrode detection. The first section discusses the design of this detector system, highlighting some of the different detector systems and configurations, such as parallel and series detectors. In the second section, a number of different example applications are described for environmental, pharmacology and industrial areas. 

Fig. 1 Parallel and series configurations for dual electrode detection systems. Wi = working electrode 1 W2=working electrode 2. (a) parallel (b) series and (c) parallel adjacent, Arrow indicates direction of flow.

This improvement can be readily seen when compared to single electrode detection shown in Fig. 2. Here the determination of p-nitrophenol (PNP) has been undertaken in human urine extracts by both dual electrode detection and single oxidative mode detection. The oxidative mode detection trace is characterised by large number of co-eluting peaks which obscure the retention time expected for PNP. However, hy DED a relative clean trace is recorded. The presence of PNP in the fortified urine extract can be readily recorded. 

Parallel dual electrode detection 4.2.1 Parallel dual electrode configurations. In the parallel mode (Fig. lb) as the name suggests, two identical electrodes are arranged... 

Figure 7 Simultaneous detection of thiols and disulfides with Hg/Au amalgamated tubular-wire dual electrode. Detection of (1) 50 J,M cysteine, (2) 100 J,M glutathione, and (3) 500 J,M glutathione disulfide. (Reprinted with permission from Ref. 47.)...

We recently described the first example of EC detection in PDMS-based microchip CE devices using a device similar to that depicted in Figure 8 [58]. Multiple gold electrodes were deposited on the glass substrate that was then covered with the PDMS separation channels. For dual electrode detection, two of these electrodes were used. The microchip format is ideal for multiple electrode detection in CEEC because it is much simpler to construct and align electrodes at the end of a planar ehannel than to reproducibly place two electrodes at the end of a fused silica capillary. 

Figure 9 Electropherogram showing dual-electrode detection in microchip CEEC using gold microelectrodes. Detection of 100 xM tyrosine, HIAA, and catechol. (Reprinted with permission from Ref. 58.)...

Zhong, M. Zhou, J. Lunte, S.M. Zhao, G. Giolando, D.M. Kirchhoff, J.R. Dual Electrode Detection for Capillary Electrophoresis/Electrochemistry. Anal. Chem. 1996 68, 203-207. 

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