2007 Annual Report
1a.Objectives (from AD-416)
To develop comprehensive methods for the determination of S and Se in proteins and free amino acids in foods. Of particular interest are the secondary metabolite (non-protein) amino acids that have been implicated in the prevention of chronic disease.
1b.Approach (from AD-416)
Proteins and free amino acids will be separated from other food components. Proteins will be hydrolyzed chemically and/or enzymatically and methionine, cysteine, selenomethionine, and selenocysteine will be determined using high performance liquid chromatography (HPLC) or reaction with cyanogen bromide. Free amino acids will be separated and derivatized for separation by HPLC or gas chromatography (GC). S and Se-containing compounds will be identified using inductively coupled plasma-mass spectrometry (ICP-MS) or pulsed flame photometric detection (PFPD). The organic component of the non-protein amino acids will be characterized using HPLC-MS with electrospray ionization.
The Food Composition and Methods Laboratory (FCML) participated in the International Pilot Study, CCQM-P86, Analysis of Total Selenium and Selenomethionine in Pharmaceutical Supplements. This study was organized by the Laboratory of the Government Chemist (London, United Kingdom) and the National Research council of Canada (Ottawa, Canada). CCQM is the Comité Consultatif pour la Quantité del Matière (CCQM) under the International Committee of Weights and Measures (CIPM). This collaboration required the exchange and analysis of a large number of sample materials.
Determination of Selenomethionine in NIST Wheat Reference Materials:
Certified reference materials are essential for the accurate determination of the selenium (Se) content of foods. Wheat is of particular concern since Se-rich soil produces high-Se wheat which is being sold at higher prices than wheat with lower Se levels. Se is primarily stored in wheat as selenomethionine (SeMet). FCML analyzed SeMet in wheat materials supplied by the National Institute of Standards and Technology (NIST) to support development of a Standard Reference Material (SRM) for Wheat. This SRM will allow labs across the U.S. to perform accurate Se analysis and will facilitate commerce.
This accomplishment addresses National Program 107 Component 1: Composition of Foods.
5.Significant Activities that Support Special Target Populations
Wolf, W.R., Goldschmidt, R.J. 2007. Updated estimates of the selenomethionine contents of nist wheat reference materials by gc-idms. Analytical and Bioanalytical Chemistry. 38:2449-2452.