Carbon Nanotube Immunosensor For The Determination Of Microcystins In Water

Nano-tube materials have potential applications because of its unique physical and chemical characteristics and important basic research significance in the area of molecular devices and composite material. As the process of the industrialization in society is speeding up now, a large number of nitrogen and phosphorus pollutants were discharged into the water by human beings, which accelerated the eutrophication of lakes and induced the bloom of algal. Microcystin-LR (MC-LR) is one of algae toxins in freshwater and is famous for its large toxic and maximum acute hazard.Electrochemical immunosensor is a kind of biosensor that combined with the electrochemical methods and the immunological techniques. In this study, We introduced the electrochemical immunosensor technology of the detection of microcystin, carbon nanotubes and TiO₂ nanotubes were modified the surface of graphite electrode respectively, and prepared a biosensor what have has electrochemical response to Microcystins, using the method of differential pulse voltammetry(DPV) to research the electrochemical properties of the modified electrode and optimizied the determination conditions of microcystin-LR (MC-LR) .Result has shown that the carbon nanotubes modified electrode has a good electrochemical behavior for MC-LR in the method of DPV. The method presented a good linear range from 10-4 up 5μg L^-1 and a limit detection of 10-5μg L^-1. The linear equation wasΔi (1e-4A) = 0.828 7logC (μg L^-1) +3.767 3 with the correlation coefficient was 0.990 1. We determined the electrode for 10 times continuously with the relative standard deviation of 2.7 %,and storaged the electrode after 28 d under 4℃with the DPV signal have no change; The electrode was applied to test natural water samples with its recovery was 88.2 % 102.5 %. In TiO₂ nanotubes modified electrode experiments, during the most optimum conditions, MC-LR standard concentration in the range of 10-5 1μg L^-1 and have a good linear relationship for the method of DPV. The linear equation wasΔi(1e-4A)=0.1422logC(μg L^-1)+0.7997with the correlation coefficient was 0.9950 and the detection limit of 10-6μg L^-1. We determined the electrode for 10 times continuously with the relative standard deviation of 2.5 %,and storaged the electrode after 28 d under 4℃with the DPV signal have no change; The electrode was applied to test natural water samples with its recovery was 99.3%～102.9 %. The sensor have high sensitivity and good stability. We investigate the electrochemical kinetics for the carbon nanotubes and TiO2 nanotubes respectively, it were showed that the Michaelis constant was 5.42 mmol / L and 3.56 mmol / L. The km was more smaller and it indicated that enzyme has more grater affinity with substrate, and the control role of the activity for enzyme become more smaller .