Preparation and certification of natural and 82Se-labelled selenomethionine reference materials

Abstract

Challenges frequently faced during the analysis of selenomethionine in complex matrices such as food and environmental samples include the lack of SI-traceable primary standards as well as difficulties associated with complex sample preparation methods resulting in potentially biased measurement results. In an effort to overcome these challenges, the National Research Council Canada has prepared two selenomethionine reference materials: a high-purity powder of natural isotopic abundance (SENS-1), and a solution of selenium-82 labelled selenomethionine (SEES-1). The purity of SENS-1, 0.961 ± 0.007 g g⁻¹ (k = 2), was established through quantitative nuclear magnetic resonance spectroscopy combined with data from inductively-coupled plasma mass spectrometry for total selenium content and the HPLC analysis of selenium-containing impurities. With the chemical purity of SENS-1 established, it was then used as the primary standard for reverse isotope dilution analysis, where the concentration of selenomethionine in SEES-1 was determined to be 1556 ± 60 μg g⁻¹ (k = 2).