Abstract
The essential trace mineral, selenium, is of fundamental importance to human health. As a constituent of selenoproteins, selenium has structural and enzymic roles. According to literatures, the bioavailability and toxicity of selenium is highly dependent on its chemical forms and their concentration. Thus, it is very important to quantitate different chemical species in the environmental and biological samples. Up to now, chemical hydridization methods are frequently employed to interface chromatographic separation and instrument detection. In view of the difficulty in converting Se(VI) into gaseous hydride by chemical methods, a new vapor generation technique utilizing HPLC-UV/nano-TiO2/HCOOH photocatalysis redox device coupled with ICP-MS for the speciation of selenium species was developed. In this study, selenite (Se(IV)) and selenate(Se(VI)), were separated using anion-exchange chromatography column packed with Nucleosil 100-5 SB under the elution of 50 mM carbonate buffer. After the chromatographic separation, on-line pre-redox of selenium species into gaseous hydrides by UV/nano-TiO2/HCOOH PCRD （photocatalysis redox device）were investigated to enhance the sensitivity of detection and reduce the non-spectral interference resulted from sample matrix. In order to enhance the hydridization efficiency, the effects of acidity, amount of TiO2 and formic acid and the reaction coil length were investigated. By way of the use of proposed procedure, Se(IV) and Se(VI) can be on-line determined after the chromatographic separation. Under the optimized condition, similar signal intensity can be reached in the use of the proposed photocatalysis redox hydride generation device. In order to validate the applicability of the established on-line system, the content of analyte species in agriculture irrigation water and human urine samples were measured. By combining with microdialysis sampling system, the feasibility to in vivo, in-situ and continuous monitor the dynamic variation of trace selenium species in urine sample has also been ascertained.