Study On Sequential Injection Coupled With Spectrophotometry For The Determination Of Vanadium In Environment Water Samples

The analysis of metals is very important in many fields, such as pharmacy medicine, food science, life science, materials science, chemical industry, geology and environmental monitoring. Some metals such as iron, vanadium, zinc and copper are trace nutrient elements that human body need. But these metals are toxic to human bodies when the concentrations exceed a certain values. Some metals such as lead, chromium, mercury and arsenic are toxic to human body. They can accumulate in various organisms and the accumulation do great harm to the human bodies.Vanadium is one kind of trace elements; it is listed as one of the cancer elements. At present, the determination of trace vanadium has many methods at home and abroad, but some instruments are expensive and need more complex operation analyzes conditions, which restrict the application of those analytical methods. Spectrophotometry is not only widely used for determination of trace elemental analysis, but also very attractive, duing to its many characteristics, such as low detection limit, cheaper instruments and simple operations. Besides, catalytic kinetic spectrophotometry has the characteristics with its high sensitivity, low detection limit, so it has become one of the most attractive method of determination of trace metal elements. This article explored two different reaction systems for determination of trace vanadium and sequential injection coupled with spectrophotometry was applied to determination of trace amounts of vanadium in environmental water samples.The first chapter of the dissertation introduced the properties of vanadium and its compound, the role in the human body, the plants and animals and diseases related to vanadium and its compound. The methods for the determination of vanadium content and the research progress is also described in this section. In addition, the purpose and significance of the topic was introduced briefly.The second section of the dissertation studied a sequential injection analysis coupled with spectrophotometry in determination of trace amounts of vanadium(V) in environmental water samples. The proposed method was based on vanadium(V) generating chelate with Xylenol Orange (XO) at room temperature and in acidic medium and the chelate produced maximum absorption at 530 nm. The absorbance was proportional to the mass concentration of vanadium(V) in the range of 0.2 to 20 μg/mL. Based on this, a new method for the determination of trace vanadium(V) was established. The relative standard deviation (RSD) for 11 repeated measurements was 0.64% at 3.0 μg/mL levels of vanadium(V). The method was applied to the determination of vanadium in water samples with satisfactory results that the recovery ranged from 80.4% to 108.6%.Catalytic kinetic photometric analysis combined with sequential injection analysis technique on the determination of trace vanadium in environmental water samples was introduced in the third section of the dissertation. The proposed method was based on in an acidic medium vanadium(IV) catalyzes the reaction of potassium bromate oxidizing Xylenol Orange (XO) at room temperature. Experimental results show that the maximum absorption of XO was reduced significantly after the catalyst vanadium(Ⅳ) being added to the reaction system, saving the decreased absorbance being proportional to the mass concentration of vanadium(Ⅳ). Therefore, we established a new method for catalytic kinetic photometric analysis coupled with sequential injection technique on the determination of trace vanadium (Ⅳ). And the factors that affect the catalytic fading reaction were studied in this part. The absorbance was proportional to the concentration of vanadium (Ⅳ) in the range of 0.5-50 ng/mL. The detection limit was 0.4 ng/mL. The relative standard deviation (RSD) for 11 repeated measurements was 0.64% at 10 ng/mL levels. The sampling frequency was 30 samples per hour. The proposed method was successfully used to the water samples, the recovery was from 91.0% to 107.8%.In the fourth chapter, a summary for the characteristic of sequential injection coupled with spectrophotometry detection technique was described.