Quantitation of Selenomethionine in Multivitamins and Selenium Supplements by High Performance Liquid Chromatography Inductively-Coupled Plasma Mass Spectrometry

VITA-1 and VITB-1 multivitamin and mineral supplement candidate reference materials from the National Research Council Canada were analyzed for their total selenium and selenomethionine contents. Following a methanesulfonic acid reflux to extract selenomethionine from the selenized yeast in the multivitamins, analysis by high-performance liquid chromatography-inductively coupled plasma triple quadrupole mass spectrometry resulted in concentrations of 7.4 ± 3.0 μg SeMet g –1 and 16.4 ± 6.5 μg SeMet g −1 in VITA-1 and VITB-1, respectively. Twelve commercially available multivitamins and selenium supplements were analyzed following the same protocol. Seven of these were noted to contain 85–115% of the selenium stated on the label; the others ranged from 5 to 147% of the claimed amount. Only one multivitamin contained selenomethionine at a concentration above the detection limit, but the amount found in the selenium supplements matched the label claims within a reasonable level of uncertainty. For comparison, two certified reference materials—wheat gluten and egg powder, both certified for total selenium only—were also examined and it was determined that selenomethionine accounted for 58% and 25% of the selenium in these food products, respectively.