Speciation Of Chromium And Selenium In Environmental Samples

With the development of speciation analysis， more and more chemists come to realizethat the beneficial or harmful of elements not only depend on its concentration， but moredepend on the speciation and transformation. On one hand， Chromium and selenium areboth known as essential trace elements for human health. On the other hand， it is also vitalfor us to identify their speciation in order to confirm whether and when these two elementsbehave as the toxicant in the environment. Trivalent chromium can regulate human bloodsugar metabolism. Lack of trivalent chromium is believed to be one of the reasons ofcardiovascular disease. However， Hexavalent chromium has very strong toxicity which isconsidered to be carcinogenic. Selenium exist in both inorganic selenium ((Se (IV)/Se (VI))and organic selenium. Compared with organic selenium which is benefit to our health，inorganic selenium is generally defined as toxic substances. Organic selenium mainly existsas selenomethionine and other forms.In this study， methods for the chromium and selenium speciation analysis which arebased on the high performance liquid chromatography coupled with inductively coupledplasma mass spectrometry (HPLC-ICP-MS) were established and studied. With thesemethods， the speciation of Chromium in the natural water， soil and commercial cementare analyzed. The main results obtained in this study are as follows:(1) A method based on HPLC-ICP-MS for simultaneous determination of Cr (III) andCr (VI) was established. The regression coefficient for Cr was over0.9998. Cr (III) and Cr(VI) detection limits were0.027μg/L and0.028μg/L respectively. The methods werevalidated by the Certified Reference Materials (CRMs) analysis and comparison， such asHexavalent Chromium in drinking water，undrinkable water and soil. The CRM ofHexavalent Chromium was purchased from USA NSI Company. The Cr (VI) concentrationvalues obtained with our method for CRMs were closely matched the provided values. Thecorresponding RSD were below4.0%. The speciation of Cr in water and soil sample wasstudied using the established method. The recoveries for Cr (III) and Cr (VI) in water were95%to108%，for Cr (III) in soil were65%to100%，and for Cr (VI) were70%to120%.The speciation results indicate that Cr in the leather industrial waste water were briefly Cr(III). Through the total analysis，total Cr in soil were very high， while the concentration ofsoluble Cr (III) and Cr (VI) were very low. Five cements were also analyzed with theestablished method. The speciation study showed Cr in cement mainly exists as soluble Cr (VI) and the concentration was found ranging from24mg/kg to197mg/kg， much higherthan the EU standard in which the content of hexavalent chromium in cement is not allowedhigher than2mg/kg.(2) A method based on HPLC-ICP-MS for simultaneous determination of seleniumspeciation was established. By comparing and studying the chromatographic separatingeffect， it was found that the separating effect of HamiltionX-100chromatographic columnis higher than the other two columns. The regression coefficient for selenium was over0.999. Selenocystine，selenocysteine，selenomethionine and seleninic acid detection limitswere1.01μg/L，0.73μg/L，0.63μg/L，0.77μg/L respectively.