Study On New Methods For The Determination And Application Of Some Heavy Metal Ions

Heavy metals have been used widely in manufacture, agriculture and pharmaceuticals industry, however, as the rapid development of modern industrial and transport, the environmental heavy metals pollution become more and more serious. Heavy metals cannot be rendered harmless by chemical or biological remediation processes and can persist in body of human and animals for long periods. Through the food chain heavy metals may deposit into human and animals body and even a little quantity can cause serious health problems which could transfer to the next generation on the genetic level. So in environmental and agricultural food monitoring it is very important to quantitatively analyze heavy metals. In this study several different methods with different sensitivities were developed to the determination some of the most common heavy metals. Besides researches of heavy metals determination, the effect of CdTe quantum dot on the photosynthetic systems of plant under ultraviolet-B radiation was also studied.1. The preparation of oligonucleotide based Hg²⁺ sensor and the application in Hg²⁺ determination.In this study a highly sensitive chemiluminescence sensor and a highly sensitive colorimetric sensor for the detection of Hg²⁺ in aqueous solution were developed by using two kind of thymine (T)-rich, mercury-specific oligonucleotide (MSO) probe. The MSO probes can form G-quadruplex DNAzyme on the effect of k+ and hemin. Mismatched thymine-thymine (T-T) base-pairs can take up the mercury ion and form inter-strand T-Hg²⁺-T complexes, which can affect the formation of DNAzymes. Through investigating the signal changes of luminol-H2O2 system (chemiluminescence) and TMB-H2O2 system (colorimetric) Hg²⁺ could be quantitative detected. The detection limit were 1×10^-10 mol L-1and 2.5×10^-9 mol L^-1respectively.2. Nafion film immobilized nano Ag-Hg amalgam glassy carbon electrode used for simultaneous determination of lead, cadmium and copperIn this work, a new route to reduce the toxicity of the mercury electrode was presented. Nafion was used as soft template to generate nanosized Ag-Hg amalgams on the surface of a glassy carbon electrode other than the traditional preparation of solid amalgam electrodes. As less mercury was used and it was immobilized by Ag and nafion film, the toxicity of mercury was reduced. Scanning electron microscope (SEM) showed that the size of the formed nano Ag-Hg amalgams was about 50 nm. Finally, the prepared electrode was used to the determination of heavy metals. Good reproducibility, linearity and sensitivity were obtained when it was utilized for the determination of Cd²⁺, Pb²⁺ and Cu²⁺ in deionized water and in tap water (without any further treatment). Different from the general methods of preparing amalgam electrodes, the method used in this work is more simple and possible to be used on different substrate materials.3. Visual determination of iron (â…¢) with mercaptosuccinic acid as color developing reagentIn this work, a simple, economical and sensitive method for Fe³⁺ determination with naked eye was presented inμg mL^-1 level. For the first time, mercaptosuccinic acid (MSA) was used to form a stable purple complex with Fe³⁺ at pH 8.0. When different quantities of Fe³⁺ were added, the color of the complex changed, which was sensitive enough to be observed with naked eye. Effects of pH and MSA concentrations were discussed to optimize the experimental conditions. Under the optimum conditions, the corresponding relationship between Fe³⁺ concentration and the color of the complex system was studied in the concentration range of 0.5-100μg mL-1. In addition, the method showed good selectivity for Fe³⁺ over Ni²⁺, Pb²⁺, Mn²⁺, Cr³⁺, Cu²⁺ and Co²⁺ when 1, 2-ethylenediamine was used as the masking agent. The feasibility of the method in the visible determination of the content of full iron (both Fe³⁺ and Fe²⁺) in human whole blood samples was approved.4. On-line preconcentration and determination of trace metals in water samples by flow injection combined with flame atomic absorption spectrometry using calix[4]arene carboxylic acid packed micro-columnThe results obtained in this work indicate that the combination of FI on-line preconcentration with FAAS is an efficient and simple method when using a micro-colum packed with calix[4]arene carboxylic acid. The developed method exhibits an excellent configuration, joining the advantages of flow injection preconcentration in terms of speediness and robustness to those of FAAS in terms of sensitivity and selectivity. When used for the determination of heavy metal ions, Cu²⁺, Pb²⁺, Co²⁺, Ni²⁺, and Cd²⁺, the present strategy provides low limits of detection, high enrichment factors and throughput after the experimental parameters have been optimized, i.e., sample pH, loading time, flow rate, and eluent concentration, volume, and flow rate. The analytical results of the target metals in certified reference materials with the present method are in good accordance with the certified values. In addition, the method has been assessed through recovery experiments when employed for the determination of trace Cu²⁺, Pb²⁺, Co²⁺, Ni²⁺, and Cd²⁺ in water samples.5. Study on the effect of CdTe quantum dots on the photosynthetic systems of Ivy under ultraviolet-B radiationWater soluble CdTe quantum dots (QDs) were synthesized and the photoluminescence wavelengths of these QDs were optimized to get the best energy transfer between CdTe QDs and the photosynthetic systems of Ivy leaves. It was well known that amylum can be produced through photosynthesis of plants and the quantum of amylum can reflect the effection of photosynthesis. Through detection of amylum it was found that the introduction of CdTe QDs can enhance the light-harvesting process and enable Ivy to absorb sunlight in a much broader spectral range. Further more, through investigation of the shape of chloroplast and counting of the number of chloroplast by cell counting chamber, it was found that CdTe QDs can reduce the harm brought by ultraviolet-B radiation.