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United States Department of Agriculture

Agricultural Research Service

Title: Organosulfur and Organoselenium Compounds: Occurrence, Importance, and Analysis

Author
item Harnly, James

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 14, 2003
Publication Date: March 15, 2003
Citation: Harnly, J.M. 2003. Organosulfur and organoselenium compounds: occurrence, importance, and analysis. [abstract]. Paper No. PO40.

Technical Abstract: Sulfur (S) and Selenium (Se) are readily interchangeable elements that have complex biological chemistry and are extremely challenging analytically. Biologically, S and Se are found in both essential, genetically coded amino acids and non-coded amino acid secondary metabolites. There has recently been considerable interest in the health promoting properties of the latter group. Amino acid secondary metabolites of sulfur (glucosinolates and S-alk(en)yl-cysteine sulfoxides) and selenium (selenomethionine, Se-alk(en)yl-selenocysteines, and -glutamyl-Se-methyl-selenocysteine), found in a variety of vegetables (most notably the Alliums and the Brassicas), have been reported to have anti-carcinogenic and anti-atherosclerotic properties. The concentration of these compounds in foods is not well known and the distribution of sulfur and selenium between compounds, as influenced by environmental factors, is even less well known. Further research on the efficacy of these compounds requires the development of appropriate analytical methods and databases. Analytically, S and Se are very dissimilar. Sulfur behaves as a non-metal and is extremely difficult to measure - it lacks strong electronic transitions and is poorly detected by atomic, emission, and mass spectrometry. In general, it is best detected as part of small molecules using organic mass spectrometry. Selenium, on the other hand, behaves like most metals with strong electronic transitions and is readily detected by atomic, emission, and mass spectrometry. In recent years, liquid chromatography-mass spectrometry (LC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) have become the analytical methods of choice for separating, detecting, and quantifying molecules and organometals of interest. Detection limits for most metals are extremely good using ICP-MS but identification of the parent molecule is strictly dependent on retention time. Consequently, LC-MS is required to identify the parent compound. Both methods are being used routinely in a complementary fashion. This complementary approach is necessary for S and Se compounds.

Last Modified: 4/17/2014