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Integrated Ag/AgCl Reference Electrode Multi-parameter Sensor For Water Quality Monitoring

Posted on:2013-06-19Degree:MasterType:Thesis
Country:ChinaCandidate:H H ZhangFull Text:PDF
GTID:2231330371986150Subject:Applied Chemistry
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Water pollution has been one of the main threats to human survival environment, and the monitoring and controlling of the polution is imperative. Oxidation reduction potential (ORP), pH, conductivity, and temperature which characterize the condition of the water quality, are important parameters in the environmental monitoring. At present the detection of these indicators depends on thelaboratory analysis equipments, which require preserved samples collecting on-site and cannot get in-situ, and continuous data. So this is necessary to develop a small, multi-parameter online testing sensor with low cost and easy maintenance. The sensor could get the testing results quickly and accurately, and also can adapt to the complex and tough test environment. It will provide great convenience for the water quality monitoring. Electrochemical sensor needs a reference electrode to define a stable and accurate electrochemical potential, and the behavior of the reference electrode is of critical importance for a reliable response of the entire sensor. Realizing the integration of the reference electrode will efficiently solve the problem of instrumentminiaturization. This thesis is mainly to fabricate Pt integrated microelectrodes using microelectromechanical systems (MEMS) technologies, and by the electrochemical modification method prepare the IrOx that could be the pH testing electrode. Electrochemical deposition the Ag/AgCl film on a naked Pt electrode, and agarose polymer is used to gel the3mol/L KCl electrolyte then coated over the Ag/AgCl film. Finally using the method of electrochemical detection monitors the water temperature, conductivity, oxidation reduction potential (ORP) and pH. The work in this disseration is presented as follows:1. Design and fabrication of the sensor. Based on the characteristics of the MEMS techniques and the basic principles of the electrochemical modified electrodes, design the process of integrated microelectrode and CME procedures, fabricate the sensor. 2. Characterization of the reference microelectrode. The electrochemical performance of the reference electrode is characterized using cyclic voltammetry.The results show that the integrated Ag/AgCl reference electrode is reliableand can provide a stable potential for electrochemical measurements. Also we test the stability, reproducibility and dependence of potential on cl~-and temperature. The results show the offset potential is no more0.2mV, and the relationship to cl~-and temperature fits the Nernstian equation very well.3. Sensor properties test. Obtain a slope of-78.19mV/pH for the macroelectrode, and the response time is3~5seconds compared with the slope of the commercial ORP instrument, the slope of the integrated ORP sensor(0.99733)is closer to the ideal value of slope (1.0000) against quinhydrone calibration solution the constant of the conductivity electrode is2.723, that means the sensor can measure the regular water conductivity the TCR value of the temperaturesensor is0.00190Ω/℃,and the resistance and the temperature has a good linear relationship.4. Sensor application. We detectd Qingcaosha’s water quality by the online test platform based on GPRS technology, and achieve the in-situ and online monitoring.
Keywords/Search Tags:Microarray, electrode, Microelectromechanical, systems, technologies, Ag/AgCl reference electrode, Multi-parameter, Water quality monitoring
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