Design of detection electrode on contactless conductivity detection in capillary electrophoresis microchip

Contactless conductivity detection has attained great attention in the last decade in capillary electrophoresis. But contactless conductivity detection is restricted by its sensitivity, how to improve detection sensitivity has become the key of contactless conductivity. In this paper a novel extended model for the detection cell consisting of a network of resistors and capacitors is proposed according to the structure of contactless conductivity detection. The effect of the detector geometry on the sensitivity of contactless conductivity is studied. By simulation, the optimal parameters are obtained. Sandwich electrode structure was established to improve the performance of the detector and minimize the stray capacitance between the electrodes. Using the optimal electrode structure, the two peaks corresponding to K⁺ and Mg²⁺ are clearly resolved with complete separation.

I. Introduction

Capillary electrophoresis (CE) technology, due to its high throughput, low sample requirement, and compactness, has been widely recognized as a powerful tool for chemical and biochemical analyses. In 1998, when Zemann and Fracassi da Silva and Do Lago independently proposed the application of the contactless conductivity detection (CCD) in capillary zone electrophoresis [1], [2]. Since then, an intense activity in this field took place [3].