Selenomethionine content of candidate reference materials

Area of Science:

• Analytical Chemistry
• Nutritional Science
• Biochemistry

Background:

• Dietary selenium is crucial for health, acting as an antioxidant.
• Accurate quantification of specific selenium forms, like selenomethionine, is essential for nutritional analysis.
• Availability of suitable reference materials (RMs) is critical for validating analytical methods.

Purpose of the Study:

• To assess two candidate reference materials (wheat gluten and selenium-enriched yeast) for the accurate determination of selenomethionine (Semet) in food.
• To validate a gas chromatography-isotope dilution mass spectrometry (GC-IDMS) method for Semet quantification.
• To evaluate the purity of a candidate selenomethionine standard material.

Main Methods:

• Gas chromatography-isotope dilution mass spectrometry (GC-IDMS) was employed.
• Samples were treated with hydrochloric acid, stannous chloride, and CNBr, followed by chloroform extraction.
• Isotopically enriched 74Semet was added to quantify naturally occurring 80Semet without protein digestion.

Main Results:

• NIST RM 8418 Wheat Gluten contains a significant portion of its total selenium as Semet.
• Commercial selenium-enriched yeast contained 73% of its total selenium as Semet (153 ± 21 μg Se(semet)/g).
• A candidate USP standard material was confirmed to be pure selenomethionine.

Conclusions:

• Wheat gluten and selenium-enriched yeast are promising candidates for Semet reference materials.
• The developed GC-IDMS method, utilizing CNBr cleavage, is effective for Semet determination.
• The study highlights the importance of pure substance standards and matrix RMs for accurate dietary selenium analysis.