Contactless Conductivity Detection Development Base On Portable Microchip Electrophoresis

Copolymerization compounds derived from perfluorooctane sulphonate(PFOS) and perfluorooctanoic acid(PFOA) have been widely applied in industry. It has shown that fluoride compounds such as PFOS and PFOA are environmental pollutants to human health, but there are still no suitable substitutes. Thus it is of great significance to investigate techniques for detecting the fluoride compounds. The existing detection techniques such as optical detection and mass spectrometry present a high requirement for test samples, and test device is hardly applicable for on-site measurement. In this thesis, microchip electrophoresis contactless-conductivity detection system was developed for on-site fluoride compounds analysis.Firstly this thesis extensively compared the existing techniques for detecting the fluoride compounds. Bared on the current progress of microfluidic chip and contactless conductivity detection, the microchip electrophoresis-contactless conductivity detection was proposed for portable instrument construction to detect the fluoride compounds.Secondly, the thesis investigated the contactless conductivity detector circuit design, including the detector circuit construction, the excitation signal selection and signal detection circuit design. The function generator MAX038 was chosen as the key compo nent and microcontroller STM32 wa s chosen for the voltage control system. This MAX038 and STM32 were used to supply excitation AC signal for the contactless conductivity detector. Current feedback circuit for the I-V conversion, signal amplification circuit and rectifier circuit were also designed. The detection circuit was simulated based on Multisim to demonstrate the feasibility of the contactless conductivity detector. Afterwards, the PCB board of the detection circuit was made and constructed.Finally, the thesis successfully established the test platform of the chip electrophoresiscontactless conductivity detector to detect the fluoride compounds. The different solution concentrations are detected based on the constructed contactless conductivity detector. It showd that this designed detector can effectively detect the concentratio n ranging from 10-2 mol/L~10-4 mol/L, thus realized the portable instrument for compounds analysis with microchip electrophoresis-contactless conductivity detection.