Novel Chemically Modified Electrode System For Trace Detection Of Lead

Heavy metal pollutants in the environment, especially the lead pollution problem, have been a cause of concern. The lead in the environment and human lead in the detection method extensively carried out. Lead is widespread in the environment and becoming a kind of highly toxic heavy metal ions. With the rapid development of modern industrial and transport, the environmental lead pollution has become a major problem affect health of human, especially for the children. It has been proved that the blood lead levels exceeding 100μ/ L will have an impact on children' s growth and development, especially damage to the neural development of children, affecting children's mental and behavior. The commonly methods for determination of blood lead include dithizone colorimetry, atomic absorption spectrometry and atomic emission spectrometry. All of these analysis methods have problems such as costly, cumbersome steps and taking long time. Compared with those methods, the electrochemical method has the advantages of low-cost and high sensitivity, which make the electrochemical method become a good choice for heavy metals detection, especially for lead.Chemically modified electrodes were prepared through various means. Controlled by the method of molecular tailoring of the electrode surface, according to the intent of the function of electrode is scheduled to have its choice to carry out the desired reaction at the molecular level to achieve an electrode function design. The current electrochemical and chemical analysis have very active research field. This modified electrode has a different character on the electrode interface with the nature. Since 1975, with the advent of chemically modified electrodes for the chemical and related interdisciplinary pioneering, an innovative and broad research field has been promised. In order to increase the sensitivity of detection, to meet the needs of real-time scene analysis, reduce costs and sample analysis requirements, the analysis of how to achieve the miniaturization of devices which are effectively chemical and biological sensors have become the important part for the miniaturization of chemical analysis and integration of the research. Based on chemically modified electrode, the sensor system has been constructed in the natural and life sciences fields and has been widely used as an effective tool for common research. The integrated and micro-electrodes have also become a hot research part. Through micro-analysis system, it can be effective in reducing the sample and reagent requirements, and reduce the cost of energy, improve the monitoring and analysis of the sensitivity, increase throughput detection.This paper is based on the above research background, focusing on how micro-analysis system can be chemically modified electrodes and the new system applied to the actual analysis of samples, laboratory research work can ultimately live with the reality of public convergence requirements of this goal, in work, with emphasis on the establishment of a more sensitive, simple and accurate heavy metals Pb (II) quantitative analysis method can be established with a view to the promotion of practical methods and the environment to lead the detection of lead ions. Therefore, this issue is of great theoretical and practical significance.This dissertation has great original and frontier innovation and includes six chapters, which are introduced separately as follows:In chapter one, we focus on the toxicity of lead on the human body, summed up the actual testing method for lead ion at first. Second, on the profile of chemically modified electrodes, we list the main preparation methods and the applications in the field of analytical chemistry. Finally, the experimental ideas of this paper and innovative ideas outlined points are pointed out.In chapter two, a blood lead testing integrated thin film electrode had been used. The CAD technology has been used to design the templates for integrated three-electrode system. With the evaporation method, electrochemical sensor technology, modern printing technology and micro-machining technology, the mass-produced integrated three-electrode system can be developed. The system had stable on the Ag/AgCl reference electrode, which was chosen out between the mixtures of Ag/AgCl electrodes and electroplating the Ag/AgCl reference electrode on the basal membrane, which makes it possible for the blood lead being tested on the integration of micro-electrode. Then we use the mercury deposition method for detection of Pb (II), respectively inspected the deposition, deposition potential, the time after the dissolution of the experimental results, and its optimized experimental conditions.In chapter three, a novel fast system based on the integrated film electrodes was created. The resulting system was successfully applied in the detection of blood lead, by means of differential pulse anodic stripping voltammetry in tiny amount of volume,～50μL, co-deposited with Hg without removal of oxygen. Under the optimum conditions, the peak current was linear to Pb²⁺ concentration from 1.2 to 70μg/dL, and detection limit was 1.2/μg/dL. Blood lead was detected with calibration curve, Y = 9. 726E-8 + X*9. 959E-8(R=0. 998). Compared with other methods reported, this method was more rapid, low-cost and could meet the requirement of real-time analysis.In chapter four, a self-assembled monolayer (SAM) of thiolatedβ-cyclodextrin (6-(2-mercaptoethylamino)-6-deoxy-β-cyclodextrin, MEA-β- CD) on a gold electrode (MCGE) was prepared. Mercury-free sensors for lead (Pb²⁺) assay based on MCGE have been developed. The analysis of Pb using MCGE-based adsorptive stripping voltammetry (ASV) includes two steps. Pb²⁺ ions are firstly adsorbed on electrode surface in a Pb²⁺ solution (5mL) during a preconcentration step, followed by a measurement step using acidic solution as medium for stripping voltammetry. Due to the strong covalent bonding of the functional groups, the MCGE-based sensors with a built-in three electrode system can be reused for tens of measurements with minimal degradation, enabling the establishment of the calibration curve and lowering the costs. Linear calibration curve was found in the range of 1.7×10^-8M to at least 9.3×10^-7M Pb²⁺ after 3min of preconcentration. Statistic analysis of the results strongly suggests the MCGE exhibited a good analytical response, while the detection limits obtained for Pb(II) was 0.71×10^-8 M (calculated from 3S/N). The modified electrodes displayed good resolution of the oxidation peaks. This work presented a new way to create a selective lead ion capturing film via modified cyclodextrin in design of specific lead sensors with high sensitivity. It has been a matter of deepening interest to quantify heavy metals in natural media such as air, soil and water, as much as in foodstuffs and biological fluids. Therefore, there has been a noticeable drive to develop diverse analytical techniques capable of detecting trace levels of the said metals in various matrices. The modified electrode to create high sensitivity highly selective mercury-free measurement sensors lead to a new approach. This electrode applied to the actual blood sample testing, the results of ICP-AES method and the results.In chapter five, the heterocyclic compounds modified electrode for detection of lead has been discussed. In this chapter, the discussions are about Morin, thiophene, pyrrole and their polymerization on the electrode surface. The article is divided into two sections. The heterocyclic compounds polymerization modified electrodes have been created. They both have a lead ion electrochemical response signal with free-mercury condition, and show a linear relationship with concentration of Pb (II). Speculate as heterocyclic polymers of the nitrogen, sulfur, oxygen atoms exist, there is a certain sequestration with Pb (II). But the role of specific mechanism still should be discussed.In chapter six, we summarized and gave objective comments on the results obtained. Meanwhile, the problems and shortcomings of this thesis were pointed out. Finally, we proposed the objects and schemes of further research.