Voltammetric Detection for Capillary Electrophoresis

Abstract

Several approaches to implementing amperometric detection for capillary electrophoresis have been reported. This report describes the development of a voltammetric detector for CE. The detector is designed to minimize distortion of the voltammetry due to ohmic potential drop. This was accomplished by using a cast Nafion detection cell at the end of the separation capillary. The cast Nafion detection cell provided a low-dead-volume, low-resistance cell that minimized ohmic potential drop and peak band broadening. The ability to detect the current due to oxidation of analytes superimposed on a large background current was also improved. A dynamic background subtraction scheme was used in which a second working electrode, positioned in the electrochemical cell but outside of the detection cell, was used to compensate for the background current in real time. The output of the compensating working electrode was subtracted from the output of the detecting working electrode prior to analog-to-digital conversion. Postexperimental digital background subtraction was also implemented. This approach provided optimal elimination of the background current with maximal detection of the analytical signal. The voltammetric detector developed produced high-quality voltammetric response of analytes with injected concentrations as low as 0.20 microM. The system was evaluated by obtaining CE voltammograms of a mixture of eight test phenolic acids.

Optimization of Electrode Alignment for Electrochemical Detection in Capillary Electrophoresis Using a Scanning Electrochemical Microscope

“…Glass-enclosed P55 carbon-fiber disk electrodes were prepared as previously described [10]. Briefly, the fibers were aspirated into glass capillaries, and then the capillary is softened and pulled around the fiber using an in-lab constructed pipet puller.…”

Recent Developments in Electrochemical Detection Methods for Capillary Electrophoresis

“…Matysik has demonstrated the use of a microfabricated array of 4 microelectrodes in this arrangement and suggested its use not only for the enhancement of selectivity but also of sensitivity by employing redox cycling [41]. A different development with similar goals has been the introduction of voltammetric detection in capillary electrophor- esis in order to obtain additional information on the peak identity [42,43]. Even fast repetitive anodic stripping analysis has been implemented as detection method and the possibility to distinguish between two comigrating species has been demonstrated [44].…”

Electroanalytical Flow Measurements–Recent Advances

“…In order to avoid the influence of high voltage used in electromigration separation, generating micro ampere currents from nano-or picoamp detection currents, several different forms of electrical decoupling were used in the off-column configuration, e.g., as porous or conductive joint to ensure electric contact with the electrolyte with a high voltage electrode, made for instance of Nafion [194,195]. Those systems are complex in design, and their application in routine use can be doubtful.…”