ARS | Publication request: ANALYSIS OF TRIGLYCERIDE AND OTHER ISOMERS BY SILVER ION CHROMATOGRAPHY: MOBILE PHASE EFFECTS ON ELUTION ORDERS AND SELECTIVITY OF SEPARATION

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract
Publication Acceptance Date: February 20, 2003
Publication Date: May 20, 2003
Citation: ADLOF, R.O., NIKOLOVA-DAMYANOVA, B. ANALYSIS OF TRIGLYCERIDE AND OTHER ISOMERS BY SILVER ION CHROMATOGRAPHY: MOBILE PHASE EFFECTS ON ELUTION ORDERS AND SELECTIVITY OF SEPARATION. ANNUAL MEETING AND EXPO OF THE AMERICAN OIL CHEMISTS SOCIETY. 2003. p. 65.

Technical Abstract: The proper choice of solvents for use in the mobile phase can significantly effect the elution orders and separation in silver ion based thin layer chromatography (Ag-TLC) and HPLC (Ag-HPLC). While theoretical principles of selectivity have been developed, most analysts choose solvent systems developed for Ag-TLC or liquid chromatography. Three major mobile phase types (toluene-, dichloromethane/dichloroethane- or hexane-based) are most often used. It is interesting to note that at present, more attention has been paid to the specific interaction of the mobile phase modifiers (acetonitrile) with silver ions or with the polar reaction sites (free silanol groups) of the silica substrate, while the major solvent component is rarely discussed. Hexane-based mobile phases have been reported to enhance resolution of component fatty acids (FA) according to the chain-length. The role of such modifiers as acetonitrile, methanol or isopropanol in the separation is widely accepted, and acetic acid has recently been used as a third component for the resolution of free fatty acids. Isopropanol (in hexane) generally has the same properties as acetonitrile and methanol for the resolution of positionally isomeric fatty acids, but its use in Ag-HPLC to resolve a series of difficult-to-separate fatty acid phenacyl ester isomers resulted in an unexpected reversal of the elution order. The contribution(s) of mobile phase, substrate, silver ion and sample conformation/components to sample retention and resolution will be discussed.