Capillary electrophoresis with capacitively coupled contactless conductivity detection: Recent applications in food control

Food quality control has become much more important during the last decade and demanded the development of robust, efficient, sensitive, and cost-effective analytical techniques. Capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) is a powerful separation method based on the different migration time rate of components in the background electrolyte solution, and it is suitable for all charged ions. There is a large number of compound groups in food that can be determined by the CE-C4D method, such as amino acids, biogenic amines, fatty acids, food additives, sweeteners, and nutrients. This paper provides an overview of recent applications of the CE-C4D in food analysis over the last decade. General conclusions and future prospects of applicability of the CE-C4D method in food analysis are presented.

A Low Excitation Working Frequency Capacitively Coupled Contactless Conductivity Detection (C4D) Sensor for Microfluidic Devices

In this work, a new capacitively coupled contactless conductivity detection (C4D) sensor for microfluidic devices is developed. By introducing an LC circuit, the working frequency of the new C4D sensor can be lowered by the adjustments of the inductor and the capacitance of the LC circuit. The limits of detection (LODs) of the new C4D sensor for conductivity/ion concentration measurement can be improved. Conductivity measurement experiments with KCl solutions were carried out in microfluidic devices (500 µm × 50 µm). The experimental results indicate that the developed C4D sensor can realize the conductivity measurement with low working frequency (less than 50 kHz). The LOD of the C4D sensor for conductivity measurement is estimated to be 2.2 µS/cm. Furthermore, to show the effectiveness of the new C4D sensor for the concentration measurement of other ions (solutions), SO42− and Li+ ion concentration measurement experiments were also carried out at a working frequency of 29.70 kHz. The experimental results show that at low concentrations, the input-output characteristics of the C4D sensor for SO42− and Li+ ion concentration measurement show good linearity with the LODs estimated to be 8.2 µM and 19.0 µM, respectively.