Abstract
Selenium is now well known as an essential element for biological systems but also as a potential toxicant. However, the nutrition, bioavailability, toxicity and cancer chemoprotective activity of selenium have been found to be species-dependent.The aim of this work is to develop analytical methods for determination of selenium species in human urine. Owing to a wide range difference in physical and chemical properties among the selenium species, two chromatographic methods based on different separation principles were employed to meet the requirement for the determination of various selenium species. Anion-exchange chromatography was used to separate selenite（Se(IV)）, selenate（Se(VI)）and trimethylselenonium ion（TMSe）, and reversed-phase chromatography to separate selenocysteine（SeCys）, selenomethionine（SeMet）and selenoethionine（SeEt）. To achieve the determination of ultratrace levels of selenium species in normal urine, a highly sensitive ICP-MS was used for selenium detection. By proper coupling of the respective chromatographic units and ICP-MS, two hyphenated systems consisting of AC-ICP-MS and RPLC-ICP-MS were established.To achieve favorable analytical performance of the on-line systems for selenium speciation, efforts were made to optimize the chromatographic parameters and to eliminate the spectroscopic interferences in ICP-MS determination. With the use of optimized analytical conditions, the detection limits as low as 0.18 ppb, 0.20 ppb and 3.45 ppb respectively for Se(IV), Se(VI) and TMSe, and 0.59 ppb, 0.26 ppb and 0.51 ppb respectively for SeCys, SeMet and SeEt were achieved. The established methods have been tested for its applicability to the analysis of urinary selenium species in healthy people. The daily change of selenium species concentration in urine samples taken from the tested individuals after uptaking selenium supplement was monitore