Amperometric Detection Circuit Design Of Capillary Electrophoresis Chip

The hotspot of Life Sciences is to develop the high-efficiency,rapid,integrated analytical method of biological samples. Because of easily being miniaturized,the capillary elcetrophoresis chip developes very rapidly. Because the sample vessel of the capillary electrophoresis chip is small,using high- sensitivity detector is extremely necessary. The application of amperometric detection is the most widespread in the domain of electrochemistry detection beeause of its high sensitivity and miniaturization. At present,the amperometric detection system is bulky and costly, which contradicts the trend of miniaturization of capillary electrophoresis chip detection system. Therefore,reducing the size of amperometric detection system,designing based on signal acquisition and control and integration of capillary electrophoresis with amperometric detection circuit becomes the research hotspot at home and abroad. This paper will use 16-bit ARM microprocessor to design a portable amperometric detection circuit, which achieves the miniaturization of amperometric detection system.This paper designs a high stability, with self-detection amperometric detection circuit. The detection circuit includes potentiostat circuit, D/A converter circuit, filter circuit, programmable gain amplifier circuit, A/D converter circuit, and so on. According to the basic principles of amperometric detection, the design potentiostat part uses I/V converter to capture micro-current signals, and uses precision op amp to collect micro-voltage signal amplifying. After filtering through the filter the signal input A/D sampling to test. Potentiostat relies on the depth of the op amp voltage negative feedback to ensure that reference electrode of constant potential, but also this paper designes a self-test circuit, which is used to detect potentiostat working condition. It ensures detection that the working electrode will be adjust between the reference electrode and the potential difference at any time.The control of amperometric detector is based on 16-bit microcontroller LPC2114. It can realize many functions through the corresponding external interface circuits and program design. These functions include programmable voltage source, the programmable gain control,proeessing the results of A/D conversion, and serial communication,and so on. The sotfwares of system adopt C language,Which achieves the A/D sampling, programmable gain amplification, and D/A conversion functions. The sotfwares control total hardwares and deteetion process so as to realize gathering and processing weak current signal real-time.Experimental results show that the potentiostat of amperometric detection System of capillary electrophoresis chip is stable, but also it can be able to better capture detection circuit micro-current signal. Experimental testing results and the theoretical value can be a good fit. Errors remain within 5.33%.