Determination Study Of Herbicide And Neutral Transmitters On Chemical Electrode And Its Application

Forensic toxicological analysis is an application of analytical chemistry in forensic medicine. It includes all kinds of biological sample analysis related to law. The establishment of a simple, quick, sensitive method is significant to reduce crimes. Paraquat and diquat have urgent toxicity and high death rate. Therefore, they are often used in suicide and murdering. For example, Ingesting PQ can cause such symptoms as liver, lung, heart, and kidney failure within several days up to several weeks, which can lead to death up to 30 days after ingestion. People who suffer high exposure to PQ are unlikely to survive. Therefore, a research to find a rapid and accurate procedure for PQ determination is urgently needed. Another report has been presented that pesticide can cause enzyme activity decrease of neurotransmitter. So, it is very important to investigate a simultaneous determination method of them.The detrmiantion study of chemical modified electrode(CME) is a method that to modified various compounds on electrode substrate to increase its sensititvity and improve characteristics. Various kinds of electrode substrate were studied. But among them, glassy carbon electdoe with polymer monolayer and gold electrode with self-assmbled monolayer attracted more attention. Recently, the biosensors prepared combining gold nanoparticles and DNA were a keypoint in researches. On the other side, people paind more attention to toxious pesiticides and neurotransmitters. The main contents are shown as follows: Part 1 Determination of neurotransmitters on safranine/GN/DNAcomposite modified glassy carbon electrode and its application.Objective: To prepare the poly(SFR)-GNP composite modified biosensor and two-layer GNPs modified electrode anchored by double-strand DNA.Methods: The modified electrodes were characterized with scan electron microscope(SEM), electrochemical impedance spectroscopy(EIS) and atomic force microscope(AFM). The electrochemical behaviors of guanine(G), uric acid(UA), adenine(A) and dopamine(DA) at the modified electrode were studied by differential pulse voltammetry(DPV). The simultaneous determinations of them were also investigated.Results: It was found the modified electrodes showed obvious electrocatalytics to the four objects. The oxide peak currents showed good linear relationships to concentrations in the range of 6.0×10-7~7.0×10-5 mol/L(dopamine), 1.0×10-6 ~ 1.0×10-4 mol/L(uric acid), 3.0 ? 10-8 ~ 1.0×10-7, 2.0×10-7 ~ 7.0×10-7 mol/L(adenine) and 1.0×10-8~1.0×10-6 mol/L(dopamine). The double-layer GNPs modified electrode showed better sensitivity than poly(SFR)-GNP composite modified electrode. The sensitive is up to nanomol.Conclusions: The investigation with the electrode of these two kinds is simple, sensitivity. The modified electrodes can be applied in the real sample determination. Part 2 Determination of neurotransmitter and herbicide on thiol/GN/DNA composite modified gold electrode and its application.Objective: To prepare the double-layer GNPs modified electrode constructed with poly(SFR) substrate and consecutive adenine DNA, and the composite modified electrode constructed with thiol substrate and consecutive adenine DNA.Methods: The modified electrodes were characterized with scan electron microscope(SEM), electrochemical impedance spectroscopy(EIS), atomic force microscope(AFM) and electrochemical quartz crystal microbalance(EQCM). The electrochemical behaviors of dopamine(DA), 5-Hydroxytryptamine(5-HT), diquat(DQ) and paraquat(PQ) at the modified electrode were studied by differential pulse voltammetry(DPV).Results: It was found the double-layer GNPs modified electrode showed better sensitivity and lower detection limit than single-layer GNP modified electrode. The modified electrodes showed obvious electrocatalytics to 5-HT, DA, DQ and PQ. The oxide peak currents showed good linear relationships to concentrations in the range of 6.0×10-8 to 1.0×10-6 mol/L(5-HT), 8.0×10-9 to 1.2×10-6 mol/L(DA), 1.0×10-9 to 1.2× 10-6mol/L(DQ) and 7.0× 10-9 to 1.5×10-6mol/L(PQ).Conclusions: The modified electrodes can be applied in the real sample determination with satisfactory reults. The methods are quick, simple, sensitivity. Part 3 Simultaneous determination of objective compounds in samplescollected by microdialysis.Objective: To investigate the application of microdialysis in separation and disposal of samples.Methods: Simultaneous determination of DA and PQ by using microdialysis at modified electrode fabricated with consecutive adenine DNA molecules and double-layer GNPs.Results: The optimum p H for simultaneous determination of them was investigated. The quantitative relationships of DA and PQ between peak currents and their concentrations were established. The linear relationships between concentrations and reduction peak currents for DA and PQ ranged from 8.0×10-8 mol/L to 8.0×10-6 mol/L and 8.0×10-7 mol/L to 5.0×10-5 mol/L, respectively. The detection limits of them were 7.0×10-9 mol/L and 5.0×10-8 mol/L. The recoveries of DA and PQ in samples were determined by microdialysis. The recoveries of DA and PQ in human blood were 30% and 24%, respectively.Conclusions: Microdialysis can be applied in separation and disposal of samples with satisfactory results.