Selenium is a nutritionally essential trace element for humans and is commercially available in dietary supplements. Several chemical forms (species) of selenium, categorized as inorganic and organic, are found in dietary supplements. Inorganically bound selenium forms include selenite (SeIV), selenate (SeVI) and chelated selenium. Organically bound selenium forms include selenoamino acids and selenized yeasts. Previous selenium speciation studies using liquid chromatography with inductively coupled plasma mass spectrometric detection (LC-ICP-MS) have indicated some selenium dietary supplements available to consumers either did not contain the labeled selenium dose or the selenium species experimentally determined was not consistent with the selenium species claimed on the product label. While these methods represent the gold standard for selenium analysis, they are lengthy and labor intensive. The presented study offers a rapid screening method using energy dispersive X-ray fluorescence (XRF) for total selenium verification and using direct analysis in real time high resolution mass spectrometry (DART-HRAM-MS) for species identification.<br/>               Total selenium and elemental speciation experiments using ICP-MS and LC/ICP-MS, respectively, have been conducted on 13 dietary supplements labeled to contain various forms and amounts of selenium. The total concentrations determined using XRF were comparable to those determined using ICP-MS for all 13 of the supplements analyzed. The DART-HRAM-MS experiments were able to rapidly determine the presence of the selenoamino acids L-selenomethione and methylselenocysteine with minimal sample preparation and a detection limit of ~100 μg/capsule (dosages are typically ~200 μg/capsule) This technique is limited to selenium containing compounds that are less than ~1,000 Daltons, thus preventing the successful analysis of supplements containing selenium enriched yeast.<br/>

Rapid screening method for selenium containing dietary supplements

253rd National Meeting (2017)

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