Construction Of Low-Cost Microfluidic Devices For Environmental Applications

With the extension of modern analytical technology and analytical instruments in different fields rapidly, the traditional analytical instruments have meet the needs of many fields for real time and on site detection, while modern analytical instruments tend to be miniaturization, integration, portability and intellectualization. Meanwhile, microfluidic devices as a representative of modern analytical instruments that can be applied in point-of-care and on-site analyses are currently receiving much attention due to its unique advantage.As a result of its low-cost, portable, easy-to-fabricate, easy-to-operate, etal, microfluidic devices can be widely applied in environmental monitoring medical diagnosis and food safety and so on. In the paper, we fabricated low-cost microfluidic devices by utilizing screen-printed carbon electrodes (SPCE) integrated with filter paper strip or home-made microchip and combined with traditional electrochemical detection methods to detect heavy metal in real sample and the sample is quantitative measured with calibration by added standards. In the mean time, the kinetics of enzyme reaction in microchip is studied. The main research contents are divided into following three parts:Part â… :Electrochemical detection of Pb and Cd in paper-based microfluidic devicesFilter paper strip is combined with screen-printed carbon electrodes (SPCE) to assemble a microfluidic device for detecting Pb(â…¡) and Cd(â…¡) in aqueous samples. The disposable microfluidic devices are demonstrated for direct quantifying Pb(â…¡) and Cd(â…¡) in aqueous samples without traditional pretreatment for physical contaminated samples. Electrochemical response of the devices is greatly enhanced and displays excellent analytical performance for Pb(â…¡) and Cd(â…¡) detection from0to100ppb with a low detection limit of2.0ppb and2.3ppb respectively. Moreover, the proposed electrochemical devices also exhibit good selectivity and stability for real samples of gas dissolved salty soda water and physical contaminated ground water. The devices are simple, low-cost, easy-to-fabricate and portable. Therefore, this analytical device should be useful for point-of-care applications in environmental monitoring, public health, and food safety. Part II:Added standards applied for stripping voltammetric detection of trace Pb and Cd in fluidic microchip integrated with screen-printed carbon electrodesHome-made microchip integrated with screen-printed carbon electrodes (SPCE) for direct detection of trace Pb(II) and Cd(II) is designed, analytes are accumulated and determined in flow system with stripping voltammetry, and the methods of standardization, added standards, are applied for self-calibration. The portable device produces a well-defined and reproducible electrochemical signal for monitoring Cd(â…¡) and Pb(â…¡), and limits of detection are low to2.0ppb and3.0ppb respectively. Meanwhile, Pb(â…¡) and Cd(â…¡) in aqueous solutions are also quantitative measured with calibration both by internal standard and standard addition method. The proposed methodology possesses the advantages of simple, fast, high sensitivity and stability. It has the potential applications in the fields of environmental monitoring, biomedical science for real-time and on-line measurements.Part â…¢:Microchip based on kinetics of enzyme inhibition applied for detection of the environment of heavy metalPaper-based enzyme immobilization combined with amperometric detection for indirect electrochemical detection of heavy metal before and after enzyme inhibition is introduced. A paper disk was immobilized with enzyme, then it was integrated on the flow cell for electrochemical detection in flow injection system. In this research, GOD was employed as model enzyme, silver ions as inhibition reagent, EDTA as regeneration reagent. When GOD was inhibited by silver ions, Glucose was introduced for electrochemical measurements before and after inhibited enzyme regeneration. Additional, the GOD enrichment of paper disk was discussed, it was be appropriate for point-of-care detection as portable device.