title: Study of UltraHigh Performance Supercritical Fluid Chromatography to measure free fatty acids with out fatty acid ester preparation.
abstract: Most lipids are best characterized by their fatty acids which may differ in (a) chain length, (b) degree of unsaturation, (c) configuration and position of the double bonds, and (d) the presence of other functionalities. Thus, a fast, simple, and quantitative analytical technique to determine naturally occurring free fatty acids (FFA) in different samples is very important. Just as for saponified acylglycerols, the determination of FFA's has generally been carried out by high resolution gas chromatography (HRGC). The use of an open tubular capillary column coupled with a flame ionization or mass spectrometric detector provides for both high resolution and quantification of FFA's but only after conversion of all free fatty acids to fatty acid methyl esters (FAME) or pentafluorobenzyl esters. Unfortunately, volatilization of labile ester derivatives of mono- and poly-unsaturated FFA's can cause both thermal degradation and isomerization of the fatty acid during HRGC. The employment of a second generation instrument (here referred to as UltraHigh Performance Supercritical Fluid Chromatograph, UHPSFC) with high precision for modified flow and repeated back pressure adjustment in conjunction with sub-2μm various bonded silica particles (coupled with evaporative light scattering, ELSD, and mass spectrometric, MS, detection) for separation and detection of the following mixtures is described: (a) 31 free fatty acids, (b) isomeric FFA's, and (c) lipophilic materials in two real world fish oil samples. Limits of detection for FFA's via UHPSFC/MS and UHPSFC/ELSD versus detection of FAME's via HRGC/MS are quantitatively compared.
authors.affiliation: Department of Chemistry, Virginia Tech, Blacksburg, VA 24061-0212, United States.
authors.forename: M
authors.initials: M
authors.lastname: Ashraf-Khorassani
authors.affiliation: Waters Corporation, 34 Maple Street, Milford, MA 01757, United States.
authors.forename: G
authors.initials: G
authors.lastname: Isaac
authors.affiliation: Waters Corporation, 34 Maple Street, Milford, MA 01757, United States.
authors.forename: P
authors.initials: P
authors.lastname: Rainville
authors.affiliation: Waters Corporation, 34 Maple Street, Milford, MA 01757, United States.
authors.forename: K
authors.initials: K
authors.lastname: Fountain
authors.affiliation: Department of Chemistry, Virginia Tech, Blacksburg, VA 24061-0212, United States. Electronic address: ltaylor@vt.edu.
authors.forename: L T
authors.initials: LT
authors.lastname: Taylor
mesh_terms: D025924:Chromatography, Supercritical Fluid / Q000379:methods*; D005230:Fatty Acids, Nonesterified / Q000032:analysis* / Q000737:chemistry; D005395:Fish Oils / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D057230:Limit of Detection
chemical_list: D005230:Fatty Acids, Nonesterified; D005395:Fish Oils
keywords: Detection limit; Evaporative light; Fatty acid ester derivatization; Fish oil; Free fatty acids; High resolution gas chromatography; Mass spectrometry; Supercritical fluid chromatography; scattering