HPLC/vapor generation/ICPMS of selenium metabolites relevant to human urine—selective determination of trimethylselenonium ion

Abstract

Selenium compounds of relevance to investigations into selenium human urinary metabolites, namely three selenosugars, the trimethylselenonium ion (TMSe), and selenomethionine, were examined with respect to their ability to form volatile compounds upon treatment with HCl and NaBH₄. All compounds investigated were detectable with HPLC/vapor generation/ICPMS. Under compromise conditions chosen for the simultaneous detection of all five compounds (0.75 M HCl, 1% NaBH₄ in 0.1 M NaOH) detection limits (0.09–0.13 μg Se L⁻¹) were in the same range as detection limits obtained by conventional HPLC/ICPMS. Vapor generation of the trimethylselenonium ion was then further investigated, because this selenium compound showed a behavior different from that of the other organic selenium compounds. The detection limit (0.003 μg Se L⁻¹) obtained with a method designed for the selective determination of this compound in human urine was more than one order of magnitude below detection limits usually achieved for selenium compounds with conventional HPLC/ICPMS. Recovery was essentially quantitative (94–99%) when urine spiked with the trimethylselenonium ion at sub μg L⁻¹ concentrations was analyzed. When background urine of a volunteer was analyzed, TMSe was detected at a concentration of 0.10 μg Se L⁻¹. The method allows the determination of the trimethylselenonium ion in urine even if it is only a trace metabolite in the presence of a large excess of selenosugars.