Highly Sensitive Detection Of Compost Microbes And Several Typical Environmental Pollutants Using Electrochemical Sensors

Electrochemical method is a modern kind of technology in environmental pollutants and environmental microbial detection, it have attracted growing interests owing to its inherent unique advantages. With the continued integration of academic knowledge and the emergence of a variety of chemically modified electrodes, electrochemical sensor became more and more common in many areas. Compost is an effective biological method of solid waste disposal, one of the main influencing factors is the microorganisms. Thus, if want to control of the composting effectively, it is very important to study the correlation parameter of microorganisms in the composting process. With the social and economic development, more and more pollutants enter in our environment, which created a devastating disaster to human survival and development, even the whole ecosystems in the earth. Heavy metals and persistent organic pollutants (POPs) are two of the typical in multitudinous environmental pollutants, therefore, it have an urgent call for methods to detect the pollutants qualitative or quantitative rapidly and accurately in the in situ measurement.A hairpin-shaped DNA probe has been designed according to the special sequence of Pseudomonas aeruginosa16S rRNA gene. The probe modified a quencher (DABCYL) at its3’end and a carboxyfluorescein (FAM) at its5’end, then the probe detect its complementary strand based on the principle of fluorescence resonance energy transfer. The probe showed a good specificity, and also obtained a linear regression of fluorescence intensity vs. the logarithm of complementary strand concentration under the optimum condition. The detection range was0.1-50nM and detection limit was0.02nM. Total RNA isolated from Pseudomonas aeruginosa using the isolate kit, the16S rRNA was analyzed by this probe, showing a good result.An electrochemical DNA biosensor based on immobilizing the hairpin-shaped DNA probe on a gold electrode for Pseudomonas aeruginosa detection was developed, streptavidin-horseradish peroxidase (HRP) was used as electrochemical activity indicator. The probe modified with a biotin at its3’end and a thiol at its5’end was immobilized onto the gold electrode surface through self-assembly. Under the optimum condition, the detection range of the electrochemical sensor was0.05～100nM, and the detection limit was0.002nM, it is obviously better than the fluorescence method. The16S rRNA extracted from Pseudomonas aeruginosa was analyzed by this proposed sensor. The results were in agreement with the reference values deduced from UV spectrometric data. The biosensor was indicative of good precision, stability, sensitivity, and selectivity.TiO2-GO intercalated composite was prepared at a low temperature (80℃) with single and multi-layered graphite oxide mixture (GO) and titanium sulfate (Ti (SO4)2) as initial reactants. The surface morphology of TiO2-GO intercalated composite was characterized by Field Emission Scanning Electron Microscope (FE-SEM). TiO2-GO intercalated composite was dispersed in0.05%Nafion solution, for fabricating the electrochemical sensing platform to determine the pentachlorophenol (PCP) by square wave voltammetry (SWV). Under the optimum experiment conditions, the SWV oxidation peak current was linearly related to the concentration of PCP, ranging from2.5×10-9M to1.0×10-7M and from5.0×10-7M to2.5×10-5M, with a detection limit of1.0×10-10M. The practical application of the proposed methods was verified in the compost sample determination.Graphite oxide was prepared from natural flake graphite, and graphene oxide was obtained via sonication. The graphene was prepared from electrochemical reduction of graphene oxide on the glassy carbon electrode, and then the graphene/GCE was modified with Nafion. Bismuth film modified graphene/Nafion/GCE was prepared by ex-situ plating for the simultaneous determination of a trace level of Pb2+and Cd2+by differential pulse anodic stripping voltammetry (DPASV). Results showed that sensitive potential stripping peak was obtained for Pb2+and Cd2+with the proposed electrochemical sensor, under the optimum experiment conditions, the detection limit of Pb2+and Cd2+was0.02μg/L and0.01μg/L, respectively. The sensor was applied to determination of Pb2+and Cd2+in fresh cabbage leaves, comparing the result with that of atomic absorption spectrometry (AAS), the concordance of results was satisfactory.