Study On Determination Of Trace Amounts Selenium(IV) By Flow Injection Spectro-photometry With Ion Association System

Selenium lies in the fourth period and the sixth main group of the periodic table of elements, and its atomic number is 34. This element was discovered by Sweden chemist Berzelius in a wasted lead chamber dregs of a H₂SO₄ producing factory in 1817. Its property is between metal and metalloid. It is known that selenium is one of the 14 trace elements, which are essential to human body. It will be harmful even lead to diseases if people take in selenium insufficiently or excessively. It has been reported that selenium is concerned with the occurrence and the development of over 40 diseases which include cancer and cardiovascular disease. Its character of pharmacology, biology and biochemistry attract people's extensive attention so much that the development of foods and drugs containing selenium is becoming a researching focus. However, the amount of selenium content in those foods and drugs is very little and it is difficult to determinate the amount of selenium. So studying on the methods of selenium determination is always an important topic in chemical field.At present, there are many methods of selenium determination, which mainly include titrimetric method of analysis, chromatographic analysis, electrochemical analysis, fluorescence method, atomic absorption specrtophotometry, flow injection analysis (FIA) and so on.In this thesis, the absorption spectral character of ternary complex of selenium (IV) has been studied in detail by conventional spectrophotometry, which is based on a reaction of selenium, thiocyanate and ethy rhodamine B (ERB) to form ternary ion-association complex in the presence of surfactant Tween-60. It has been discussed the factors affecting the proposed system above, which include maximum absorption wavelength, reaction acidity, reaction temperature, reagent levels, reagent order and selectivity. The reaction mechanism of complicated sorption ion-association complex has been preliminarily studied. Meanwhile, the optimum analytical condition of the motioned system above has been researched by conventional spectrophotometry: the maximum absorption wavelength is 605 nm; the apparent molar absorptivityε605 is 1.50×10⁶ L·mol^-1·cm^-1; Beer's law is obeyed in the concentration rang of 0.25～2.0μg/25 mL; the detection limit of the method is...