Author
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Adlof, Richard |
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Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Abstract Only Publication Acceptance Date: 10/3/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Silver ion HPLC (Ag-HPLC), utilizing columns packed with 5-10 micro Nucleosil SA (TM) [phenylsulfonic acid groups bonded to a silica substrate] or similar substrate in which the sulfonic acid protons have been exchanged with Ag ions, has been proven to be a versatile technique for the analytical and semi-preparative separation of lipid and lipoprotein structures by the number and/or configuration of the unsaturation. Separation of geometrical (cis/ trans) or positional isomers (mono-, di- and triglycerides; fatty acid esters) is due to the interaction of the silver ions with olefinic or acetylenic bond pi-electrons and, to a lesser degree, the unpaired electrons of the fatty acid carbonyl oxygen(s). Ag-HPLC has been used to separate 15 of the 16 cis/ trans isomers of methyl arachidonate (5,8,11,14-20:4), an accomplishment far exceeding the capabilities of current capillary gas chromatographic, HPLC, or other analytical methodologies. Ag-HPLC solvent systems usually contain dichloromethane, dichloroethane, and small amounts (0.01% to 0.025%) of acetonitrile (ACN). An isocratic, UV-compatible solvent system containing hexane (later heptane) and small (<1.5%) amounts of ACN was introduced in the late 1980's/early 1990's. Recent advances in Ag-HPLC include improved separation efficiency and sample capacity by the coupling of three or more columns in series and the increased application of Ag-HPLC in "hyphenated" techniques such as Ag-HPLC/GC or Ag-HPLC/MS. |
