Liquid chromatography-electrospray ionization tandem mass spectrometry for on-line characterization,monitoring and isotopic profiling of the main selenium-metabolite in human urine after consumption of Se-rich and Se-enriched food

摘要

The metabolism of selenium (Se) in the human body has yet not completely been unravelled and hence,an efficient method for characterization and on-line monitoring of the main Se-compound in human urine after consumption of Se-rich food was developed.Total Se-concentration in human urine after consumption of several Se-rich products was measured with inductively coupled plasma mass spectrometry (ICP-MS).The highest Se concentration in urine was observed after 4-10 h.The urine samples were brought onto a reversed phase column and the Se was detected by ICP-MS.Parameters for liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) measurements were optimized by using commercially available sugars,because it is known that some of the urinary metabolites contain a sugar moiety.In order to characterize the predominant Se-metabolite,it was necessary to extensively clean-up the sample and preconcentrate the species.The main metabolite was measured on its precursor ion on three different m/z according to three isotopes of Se.Relative peak surfaces matched the relative abundances of the isotopes.The product ions could be measured in a human urine sample in accordance to the product ions of the commercially available sugars.Moreover,the evidence of a selenosugar was demonstrated by the use of the Se-isotopes when measuring the product ions.LC-ESI-MS-MS was proven to be very efficient for the characterization of the main urinary Se-metabolite and can be used for on-line monitoring of the compound in urine samples.The method can be extended for clinical screening after consumption of Se-(en)rich(ed) food by use of the Se-isotopic profile and/or of the typical product ions of (methyl)-N-acetyl-hexosamines.