| The health inspection significance and research status of determination of trace uranium and chromium in the environment were outlined, respectively. The basic concepts and principles for the cloud point extraction and secondary extraction techniques in sample handling were introduced. And the basic principles and the quantitative determination basis for three analysis methods of health inspection for trace uranium and chromium in this topic were expoundedChapter 2: In this chapter, a new catalytic kinetic fluorimetric method has been proposed for determine the U(VI) in environmental samples. In sulfuric acid medium, uranium( exists in the form of UO22+) can catalyze the oxidation-reduction reaction of potassium bromate with fluorescence reagents rhodamine G(Rh G), which leads to the decrease of fluorescence intensity of the system. There is a linear relationship between the reduce value the fluorescence intensity of reaction system(ΔF) and the concentration of uranyl ions(c). The experiment show that the excitation and emission wavelengths are 525 and 552 nm, respectively. Under the optimum condition, the determination liner range was 6.62 × 10-9 ~ 5.2 × 10-8 g/m L for U(VI). The Linear regression equation was ΔF = 22.2 + 52.6 c( g/m L), the correlation coefficient r = 0.9992. The detection limit for U(VI) was 2.0×10-9 g/m L, and the RSD were 2.8%- 4.6%. This method is simple, and has high precision,good accuracy and the low detection limit. The recoveries were in the range of 99.3% ~ 102.5%. Used in the detection of U(VI) in environmental water samples, the result was satisfactory.Chapter 3: In this chapter, on the basis of the second chapter, a new photocatalytic kinetic fluorimetric method for determine the U(VI) in complex samples has been proposed based on the combination of two times cloud point extraction and photo-catalytic kinetic fluorescence detection. In MES-Tris buffer solution, uranium(VI) can combine with salophen to form U(VI)-salophen complex which can photocatalyze the oxidation- redox reaction of potassium bromate with Rh G and lead to the decrease of fluorescence intensity of the system. The reduce value of fluorescence intensity of reaction system(ΔF) is in proportional to the concentration of uranyl ions(c). The system excitation and emission wavelengths are 525 and 553 nm, respectively. Under the optimum condition, the determination liner range was 4.0×10-12- 4.0×10-11 g/m L for U(VI). The Linear regression equation was ΔF =11.9- 31.2c(g/m L), the correlation coefficient r = 0.9902. The detection limit for U(VI) was 1.46×10-12 g/m L, and the RSD were 2.6%-3.8% This method is simple, and has high precision,good accuracy and the low detection limit. The recoveries were in the range of 99.6%-101.5%. Used in the detection of U(VI) in environmental water samples, the result was satisfactory. Compared with the second chapter, the method of lower detection limit.Chapter 4: The properties of fluorescence of Rhodamine 6G( Rh6G) were studied. Rh6 G itself has a strong fluorescence signal which the excitation and emission wavelengths are 525 and 555 nm. Based on the catalytic effect of chromium(VI) on the oxidation reaction of Rh6 G by potassium bromate in acetic acid- sodium acetate buffer solution, a catalytic kinetic fluorescence method was proposed for the determination of trace chromium(VI). The decrease intensity of fluorescence(ΔF) was in proportional to the concentration of Cr(VI). The Linear regression equation was ΔF =2646.4c(μg/m L)- 4.57, the correlation coefficient r = 0.9987.The detection limit and the linear range for Cr(VI) were 3.46 × 10-9 g/m L and 1.0 ×10-8- 1.4 ×10-7 g/m L, respectively. The Cr(VI) in environmental water samples were analyzed by the proposed method with satisfactory results. The recovery of environmental water was 95.5%-102.9% and the RSD was less than 4.9%. This method is sensitive, exact, simple and easy to do. |
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