Study On Sequential Injection Coupled With Chemiluminescence For The Determination Of Cyanide And Nitrite In Environmental Water Samples

With the development of science and technology, the progress of the times and the rapid growth of population, the natural environment is continuous affected and changed by human activities. Since the eighteenth century industrial revolution, human has made unprecedented achievement in nature transforming and economic development. At the same time, owing to the mismanagement of industrialization progress and the irrational exploitation of natural resources, the environment human lived is contaminated and ecological system is also destroyed subsequently. So the environmental problems have already developed from the regional to the global. Among them, water pollution has already posed a significant threat to human security and becomes a major barrier to human health and sustainable development. It is one of the world’s top environmental problems. Therefore, establishing quick, convenient, sensitive, selective and reliable methods for the detection of pollutants at low levels will be more competitive, and it will be more meaningful to the control of environmental pollution, the monitor of water quality and the health of human beings.Chemiluminescence (CL) method is an attractive and powerful detection technique owing to its analytical advantages such as low detection limit, very high sensitivity, wide linear dynamic range, fast response and simple equipment, and it has become one of the hottest research fields in the analysis of trace and ultra trace amount of inorganic, biological and organic materials. At the same time, sequential injection analysis (SIA) was developed as a branch of sampling means of FIA or second generation FIA with the advantages of high degree of automation, low consumption and good reproducibility. When chemiluminescence detection was coupled with SIA analysis, its features were reserved, and the shortcomings, such as inconvenience of reaction process control and poor repeatability caused by fast reaction, were overcome. Combination CL with SIA remarkably improved the repeatability, accuracy and analytical frequency of the determination results. In this dissertation, the sequential injection coupled with chemiluminescence detection technique was proposed and applied to the determination of cyanide and nitrite and satisfactory results were obtained.The first chapter of the dissertation introduced the concept, classification, origin, harm of cyanide and the review on the progress of analytical methods for the determination of cyanide in recent years. The methods including volumetric method, chromatography, mass spectrometry, electrochemistry, spectroscopic method and flow injection analysis and so on were evaluated in detail. The paper also described the separation method in the flow analysis and the application of gas-liquid separation system such as online gas diffusion.The second chapter of the dissertation described a sequential injection online gas diffusion coupled with chemiluminescence in determination of cyanide in water samples. The proposed chemiluminescence procedure is based on the direct reaction of Cu (Ⅱ)/CN-and luminol in the alkaline medium. In which, luminol is first oxidized to the luminol free radical by the single electron antioxidant (Cu (CN)42-), then form aminophthalate ion and emit light at425nm. The chemiluminescence intensity is linearly related to the concentration of cyanide. When the technique of online gas diffusion was not used for the pretreatment, the chemiluminescence intensity is proportional to the mass concentration of cyanide in the range of0.5-250μg/L with a correlation coefficient of0.9990. The relative standard deviation (RSD) for11repeated measurements is0.66%at10μg/L levels and0.46%at100μg/L levels respectively. The sampling frequency is200samples per hour. The detection limit (3σ) is0.03μg/L. The percentage of recovery for the determination of cyanide in environmental samples is over90.4%-109.8%. When the online gas diffusion was used to improve the selectivity of the method, under the optimum condition, the linear response range is5-700μg/L with a correlation coefficient of0.9975. The detection limit (3σ) is0.20μg/L. The relative standard deviation (RSD) for11repeated measurements is1.5%at30μg/L levels and1.3%at300μg/L levels, respectively. The sampling frequency is41samples per hour. The method was applied to the determination of cyanide in the environmental water samples and the recovery is over92.5%-109.3%.The third chapter of the dissertation, a fast sequential injection system with chemiluminescence detection for the determination of nitrite in water samples was proposed. Nitrite reacts with H2O2in acid medium to form peroxynitrous acid that is subsequently detected as peroxynitrite by the chemiluminescence reaction with alkaline solution of luminol. Within a certain range, the chemiluminescence intensity is linearly related to the concentration of nitrite. The CL intensity is proportional to the concentration of nitrite in the range5.0X10-9-1.0×10-7mol/L and1.0×10-7-7.0×10-6mol/L, respectively. The detection limit (3σ) is2.3×10-9mol/L. The relative standard deviation for eleven repeated measurements is0.77%at5.0×10-8mol/L levels and0.54%at3.0×10-6mol/L levels, respectively. The sampling frequency is120samples per hour. The method was applied to the determination of nitrite in the environmental water samples and the recovery is over88.0%-116.3%. The determination result of the national standard material (GSBZ50006-88) was in agreement with the certified value.In the last chapter, a summary for the characteristic of sequential injection coupled with chemiluminescence detection technique was described.