Electrophoresis with Electrochemical Detection

Department of Pharmaceutical Analysis, School of Pharmacy, Fudan University, 826 Zhanheng Road, Shanghai, 201203, China 

Edited by Alberto Escarpa, Maria Cristina Gonzalez and Miguel Angel Ldpez. 2015 John Wiley Sons, Ltd. Published 2015 by John Wiley Sons, Ltd. 

This chapter focuses on recent advances in the application of CE-ECD for analyzing bioactive constituents in foods and agricultural products. This field of study has grown considerably in the past decade. The following sections will cover the commonly used separation modes of CE in agricultural and food analysis, CE-ECD system, the applications of CE-ECD in the determination of nutritions, phenolic compounds, purines, and food additives in foods and agricultural products as well as future prospects. 

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Fig. 3.172. Non-aqueous capillary electrophoresis with electrochemical detection of a dye mixture containing (a) 1.7 jUg/ml malachite green, (b) 0.70 jug/ml crystal violet, (c) 4.3 /ig/ml rhodamine B, and (d) 9.1 X 10-6 M ferrocene. Experimental conditions capillary dimensions, 95 cm X 75 pm i.d. running electrolyte, acetonitrile containing 1 M HAc and 10 mM NaAc electrokinetic injection, 20 s 5 kV separation voltage 20 kV applied detection potential, 1.55 V. Reprinted with permission from F.-M. Matysik [206].

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Spectroscopic detection techniques (UV, fluorescence) are the most common methods of detection employed in CE. UV detection, although the simplest method of detection to adapt to CE, suffers from a loss of sensitivity due to the extremely small pathlengths involved in CE. Laser-induced fluorescence detection is much more sensitive, but is limited by the number of wavelengths available for excitation. In addition, this technique is very expensive to implement and maintain. Electrochemical detection has several advantages for CE [47]. Since electrochemical detection is based on a reaction at the electrode surface, the cell volume can be very small without loss of sensitivity. The concentration-based limits of detection for capillary electrophoresis with electrochemical detection (CEEC) are comparable to those of LCEC. 

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Other methods have also been successfully employed in the isolation procedure of stilbenoids, including MPLC [209,299,326], preparative TLC [208,277,299], centrifugal partition chromatography (CPC) [359,360] and the support-free technique of multilayer coil countercurrent chromatography (MLCCC) [32]. A method based on capillary electrophoresis with electrochemical detection (CE-ED) was employed for the determination of oligomeric stilbenes found in the roots of Caragana species [361]. 

Figure 12.10. (a) Electrokinetic microinjector and (b) electropherogram generated from the removal and separation of cytoplasm samples from single nerve cells of Planorbis corneus, a pond snail.8 [Reprinted, by permission, from R. A. Wallingford and A. G. Ewing, Anal. Chem. 60 (No. 18), 1988, 1972-1975. Capillary Zone Electrophoresis with Electrochemical Detection in 12.7 pm Diameter Columns . 1988 by American Chemical Society.]... 

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Electrochemical Techniques, Fig. 1 Schematic of capillary electrophoresis with electrochemical detection system. (a) High-voltage supply, (h) grounded platinum electrode, (c) reference electrode, (d) auxiliary platinum electrode, (e) detection electrode, (/) running buffer, (g)... 

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