A Novel Planar Grounded Capacitively Coupled Contactless Conductivity Detector for Microchip Electrophoresis.

Jianjiao Wang,Hui You,Yuanfen Chen,Yaping Liu,Wenhe He

doi:10.3390/mi13030394

Abstract

In the microchip electrophoresis with capacitively coupled contactless conductivity detection, the stray capacitance of the detector causes high background noise, which seriously affects the sensitivity and stability of the detection system. To reduce the effect, a novel design of planar grounded capacitively coupled contactless conductivity detector (PG-C4D) based on printed circuit board (PCB) is proposed. The entire circuit plane except the sensing electrodes is covered by the ground electrode, greatly reducing the stray capacitance. The efficacy of the design has been verified by the electrical field simulation and the electrophoresis detection experiments of inorganic ions. The baseline intensity of the PG-C4D was less than 1/6 of that of the traditional C4D. The PG-C4D with the new design also demonstrated a good repeatability of migration time, peak area, and peak height (n = 5, relative standard deviation, RSD ≤ 0.3%, 3%, and 4%, respectively), and good linear coefficients within the range of 0.05–0.75 mM (R2 ≥ 0.986). The detection sensitivity of K+, Na+, and Li+ reached 0.05, 0.1, and 0.1 mM respectively. Those results prove that the new design is an effective and economical approach which can improve sensitivity and repeatability of a PCB based PG-C4D, which indicate a great application potential in agricultural and environmental monitoring.

Highlights

Microchip electrophoresis has the characteristics of small size (~cm2 ) and short separation channels, which is efficient and convenient for on-site and real-time detection
Electrical field simulation and baseline strength test showed that the stray capacitance of planar grounded C4D (PG-C4D) was less than 1/3 of that of traditional C4D
The background baseline intensity of the PG-C4D was less than 1/6 of that of traditional C4D, and the noise amplitude of baseline was reduced from 25 mV to

Summary

Introduction

Microchip electrophoresis has the characteristics of small size (~cm2 ) and short separation channels, which is efficient and convenient for on-site and real-time detection. C4D technology has been widely applied in capillary electrophoresis and microchip electrophoresis [1–4]. C4D was first proposed independently by Zemann et al [5] and da Silva et al [6], applied in capillary electrophoresis. Pumera and Wang [7] replaced the tubular electrode in C4D with two flat aluminum sheets and applied it in microchip electrophoresis. When the sample passed through the detection cell along the channel, the change of the local impedance caused the change of the alternating current on the pick-up electrode. After rectification, filtering, and amplification, the current on pick-up electrode was sampled and displayed as peaks [8,9]

Methods

Results

Conclusion