| It has become a noteworthy problem for environmental pollution in all over the world, and most environmental pollutants have an invaluable potential threat for biology and human health.Persistent Toxic Substances (PTS) which affecting human survival and health, are known as the three major environmental problems in 21st century, as well as the greenhouse effect and ozone depletion. Whether the 21 categories of Persistent Organic Pollutants (POPs) identified in "the Stockholm Convention", the 12 categories of Persistent Bioaccumulative & Toxic Chemicals (PBT) identified by U.S. EPA, or the study of Environmental Endocrine Disruptors (EEDs), they are closely related with PTS. Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are two types of typical persistent toxic substances. They are widely distributed in the environment, but mostly trace, and difficult to degrade, with a high fat-soluble, water-insoluble, and easy to bioaccumulation. Moreover, they are not only carcinogenic, teratogenic and mutagenic, but also have the role of endocrine disruptors. Phenolic compounds are also harmful to ecosystems. Some phenolic compounds are endocrine disrupting chemicals or metabolite of them.Based on the assessment of the health hazard and dose response for pollutants, it is vital to determine the concentration of environmental pollutants. The concentration of pollutants is always trace, so it is significant to found specific, rapid and direct analytical techniques to convenient for the emergency monitoring and simple monitoring of the environmental pollutants and better understand the long-term, health effects of chronic exposure to them. Because of sensitivity and convenience, the electrochemical detection technique has broad application prospects in the analysis of environmental pollutants. In particular, combining the immunology with the electrochemical sensing techniques is considered to be hot topics of current research in organic pollutants detection. How to construct high sensitive and selective sensing interface is a key for the preparation of novel chemically modified electrode and electrochemical biosensor, which has become one of the research subject of keen interest for environmental analysts.In this thesis, novel polymer modified electrodes and electrochemical immunosensors were fabricated based on two types of sensing interfaces, after which the electrochemical behaviors were studied in details. The new polymer modified electrodes and electrochemical immunosensors were used for amperometric determination of naphthol, hydroquinone, bisphenol A, some of polycyclic aromatic hydrocarbons and polychlorinated biphenyls. The main contributions are summarized and presented as follows:1. Acridine orange was electropolymerized on a glassy carbon electrode by using a potentiodynamic technique to construct a catalytic interface for the investigation of naphthol. The electrochemical behaviors of 1-naphthol on the modified electrode were studied by determining the influences from solution acidity, the scan rate, the accumulation time, and the working temperature. Experiments showed that the poly(acridine orange) film electrode demonstrated electrocatalytic activity to the electrooxidation of 1-naphthol giving a greatly improved detection limit down to 8×10-8 mol·L-1 (S/N=3) at the optimal experimental condition, and the oxidation peak current from the poly(acridine orange) film electrode was linearly proportional to the concentration of 1-naphthol in the range of 2×10-7～3.2×10-6 mol·L-1 and 5.2×10-6～1.2×10-4 mol·L-1. The detection of 1-naphthol in tap water and river water was carried out with satisfactory results. The modified electrode for 1-naphthol determination was better than that in previous studies in electrocatalytic activity and linear range. Some environmental samples were analyzed with satisfactory results, including specificity and recovery rate. The results were accordant to high performance liquid chromatography (HPLC), indicating that the method for the detection of environmental pollutants was feasible and effective.2. Crystal violet was electropolymerized potentiodynamically on a glassy carbon electrode to construct a catalytic interface. The electrochemical behaviors of hydroquinone on the poly(crystal-violet) film modified electrode were studied systematically with respect to different solution acidities, accumulation time, scan rates, and so on. The reaction process of hydroquinone on the poly(crystal-violet) film modified electrode was discussed. Experiments showed that the poly(crystal-violet) film modified electrode exhibited excellent catalytic effect and selectivity on the electrochemical behavior of hydroquinone coexisting with dihydroxybenzene isomers. The method was applied to determination of hydroquinone in the actual waste water, and compared with HPLC. The results were satisfactory and reliable.3. Bisphenol A is environmental endocrine disruptors and has been identified as priority pollutants in many countries. Acid blue 62, a kind of dye monomer containing aromatic ring, was electroploymerized on glassy carbon electrode to form poly (acid blue 62) film modified electrode for the investigation of bisphenol A. Under the optimal experimental condition, the response of oxidation peak current on the polymer modified electrode was greatly increased and oxidation peak potential shifted negatively 100 mV compared with a bare electrode. The detection limit of bisphenol A was 2×10-8 mol·L-1. After 45 days storage in the air, the 92% of the initial response current was remained suggesting the good stability of the polymer modified electrode. The mothod was used to detect bisphenol A in food packaging materials and compared with HPLC. The results were satisfactory and the method provided new thoughts for the determination of bisphenol A in environment and food.4. The thiourea was self-assembled on a gold electrode via Au-S covalent bond and then yielded an interface with amine groups for the self-assembly of colloidal Au to immobilize naphthalene polyclonal antibodies and retain their activity efficiently. The preparation, characterization, and amperometric measurement of relevant properties of the immunosensor were studied. Under the optimized working conditions, the current response of the immunosensor was proportional to the concentration of naphthalene in the range of 0.5～100 ng·mL-1 with a detection limit of 0.08 ng·mL-1. The fabricated immunosensor exhibited good biocompatibility, high immobilization amount of antibody, good immunoreaction activity and easy regeneration. This method was applied to the naphthalene detection in environmental samples with satisfactory results. The method was accordant to HPLC.5. A label-free amperometric immunosenor for fast and sensitive detection of anthracene is developed. A layer of prussian blue was initially electrodeposited onto a glass carbon electrode as an electronic mediator, and then nano-gold layer was formed on PB film by electrochemical reduction of HAuCl4 solution under the potentiostat. Then L-cysteine and nano-gold particles were self-assembled layer-by-layer. Finally, the anti-anthracene was adsorbed onto the bilayer nano-gold particles to construct a sensitive immunosensor. The characteristics of the modified electrode at different stages of modification were studied by cyclic voltammetry. Based on the change of the current after antigen-antibody reaction, the concentration of anthracene was detected. At the optimized working conditions, the current response of the immunosensor was proportional to the concentration of naphthalene in the range of 0.1～120 ng·mL-1 with a detection limit of 0.02 ng·mL-1. The mothod was compared with HPLC and the differences are acceptable within the margin of error. The studied immunosensor exhibited low detection limit, long-term stability and the possibility of repeated regeneration.6. Chitosan had affinity for nano-gold particles through lots of amine groups and the anti-PCB77 was adsorbed onto the nano-gold particles to construct a sensitive immunosensor for determination PCB77 in environmental soil samples. Cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy were adopted to monitor the regular growth of the multilayer films and optimize the experimental conditions. The mechanism and properties of the immunosensor were examined in detail. Experimental results showed that the method increased the immobilization amount of antibody and enhanced the sensor sensitivity and selectivity. At the optimized working conditions, the detection limit was 0.01 ng·mL-1. The proposed mothod was used to analyze of real environmental samples with satisfactory results. The results detected by immunosensor were compared with that from GC/MS, showing a good correlation, and the differences between two results are acceptable within the margin of error. In this paper, chemical and biological sensor technologies are applied to determination of phenolic compounds, PAHs and PCBs pollutants in real environmental samples. The results are satisfactory and reliable. These studies may provide new thoughts for the construction of high sensitive and selective electrochemical sensing interfaces and extending the application of electroanalytical techniques in environmental monitoring.
|
PDF Full Text Request