title: Preparation, isolation and identification of non-conjugated C18:2 fatty acid isomers.
abstract: Non-conjugated geometric/positional isomers of linoleic acid (c9,c12-18:2) are often present in processed foods and oils. The following work presents a simple addition/elimination reaction for preparation of non-conjugated 18:2 fatty acid isomers. A mixture containing positional and geometric isomers of C18:2 fatty acids was produced by addition of hydrobromic acid to the fatty acid double bonds, followed by its elimination with a strong sterically hindered base. Pure 8,12-, 8,13-, 9,12-, and 9,13-18:2 fatty acid methyl esters were isolated from the synthetic mixture by a combination of sub-ambient RP-HPLC and Ag+-HPLC. The determination of the double bond position was achieved by GC-MS using picolinyl esters derivatives. The determination of the fatty acid double bond geometric configuration was obtained by partial hydrogenation of the isolated isomer with hydrazine, followed by the GC-FID analysis.
authors: Office of Regulatory Science, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, 5100 Paint Branch Pkwy, HFS-715, College Park, MD 20740, USA. Electronic address: alireza.fardinkia@fda.hhs.gov.
authors: Ali Reza
authors: AR
authors: Fardin-Kia
mesh_terms: D004952:Esters / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006834:Hydrazines / Q000737:chemistry; D007536:Isomerism; D010084:Oxidation-Reduction; D010848:Picolinic Acids / Q000737:chemistry*
chemical_list: D004952:Esters; D005227:Fatty Acids; D006834:Hydrazines; D010848:Picolinic Acids; C029424:hydrazine
keywords: Fatty acid; Fatty acid separation; Fatty acid/synthesis; Hydrazine reduction; Linoleic acid; Liquid chromatography; Mass spectrometry; Methods/HPLC; Picolinyl esters