Determination Of Trace Selenium In Foods By Hydride Generation Atomic Fluorescence Spectrometry

Selenium is a necessary trace element for the health of people. In recent years, many investigations show that many diseases are related to intaking level of selenium. At today when selenium is known more clearly, the determination of selenium in selenium-containing materials and selenium-containing biological matairals become more important for the study of selenium. The roles of selenium in biological systems and geochemical cycle not only depend on the total content of selenium but also depend on the forms in which it is present and the content of these forms. Although many works have been done in the fields of determanation and speciation of selenium, developing applied method to detect selenium in environment, appling hyphenated techniques to prove up the biological behavior of different chemical and biological forms are significant. Atomic fluorescence spectrometry(AFS) is an analytical technique which have been developed since 1960'.The technique has many virtues such as simple spectral line,high sensitivity,low detection limit and multi-element analysis.Hydride generation(HG) thchnique has the virtues of separating from matrix,eliminating interference of matrix,enriching elements, high sampling efficiency, apting to realize automatic analysis,speciation.In this paper,hydride generation-atomic fluorescence spectrometry(HG-AFS) was used to determine selenium in foods;the innovation of the paper was that the influence of surfactant on the determination of selenium was studied and on the basis, Se(Ⅵ),Se(Ⅳ)and organic selenium in Kangbixi were determined. Part Ⅰ:A method was developed for the determination of trace selenium in selenium-enriched foods by intermittent flow-hydride generation-atomic fluorescence spectrometry. Samples were digested with a mixture of nitric acid and perchloric acid, potassium ferricyanide acted as masking agent. Under the optimized conditions, the working curve was linear in the range of 100μg/L and the correlation coefficient was 0.9999. The detection limit was 0.065μg/L. When the method was applied to determine trace selenium in eggs, selenium-enriched rice, and selenium-enriched salt the recoveries were 90.6%, 98.5%, and 104.3% respectively. Part Ⅱ:Instrument and hydride generation conditions were optimized with orthogonal experiment;under optimized conditions,the influence of anionic surfactant,cationic surfactant and nonionic surfactant on the determination of selenium was studied; when the concentration of CTAB was 0.1～0.8×10-5mol/L,the intensity of signal was enhanced 22.72% compared with the intensity of signal in water media,so the sensitivity was improved.In the media of 0.2×10-5mol/L CTAB,a three-fold improvement in detection limit was obtained;at the same time, the levels of tolerance of interfering elements in the selenium determination were increased, the effect was even more remarkable for Cu2+. Selenium in Kangbixi was determined in the media containing 0.2×10-5mol/L CTAB.In order to quantitatively extract selenium in Kangbixi,the extracting condition and extracting percentage were investigated.Se(Ⅵ)was reduced to Se(Ⅳ)with 6mol/L HCl. Se(Ⅵ),Se(Ⅳ)and organic selenium in Kangbixi were determined, as a result ,99.5% selenium in Kangbixi was organic selenium.