title: Glycidyl fatty acid esters in food by LC-MS/MS: method development.
abstract: An improved method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of glycidyl fatty acid esters in oils was developed. The method incorporates stable isotope dilution analysis (SIDA) for quantifying the five target analytes: glycidyl esters of palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2) and linolenic acid (C18:3). For the analysis, 10 mg sample of edible oil or fat is dissolved in acetone, spiked with deuterium labelled analogs of glycidyl esters and purified by a two-step chromatography on C18 and normal silica solid phase extraction (SPE) cartridges using methanol and 5% ethyl acetate in hexane, respectively. If the concentration of analytes is expected to be below 0.5 mg/kg, 0.5 g sample of oil is pre-concentrated first using a silica column. The dried final extract is re-dissolved in 250 μL of a mixture of methanol/isopropanol (1:1, v/v), 15 μL is injected on the analytical C18 LC column and analytes are eluted with 100% methanol. Detection of target glycidyl fatty acid esters is accomplished by LC-MS/MS using positive ion atmospheric pressure chemical ionization operating in Multiple Reaction Monitoring mode monitoring 2 ion transitions for each analyte. The method was tested on replicates of a virgin olive oil which was free of glycidyl esters. The method detection limit was calculated to be in the range of 70-150 μg/kg for each analyte using 10 mg sample and 1-3 μg/kg using 0.5 g sample of oil. Average recoveries of 5 glycidyl esters spiked at 10, 1 and 0.1 mg/kg were in the range 84% to 108%. The major advantage of our method is use of SIDA for all analytes using commercially available internal standards and detection limits that are lower by a factor of 5-10 from published methods when 0.5 g sample of oil is used. Additionally, MS/MS mass chromatograms offer greater specificity than liquid chromatography-mass spectrometry operated in selected ion monitoring mode. The method will be applied to the survey of glycidyl fatty acid esters in food products on the Canadian market.
authors.affiliation: Food Research Division, Bureau of Chemical Safety, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada. adam.becalski@hc-sc.gc.ca
authors.forename: A
authors.initials: A
authors.lastname: Becalski
authors.forename: S Y
authors.initials: SY
authors.lastname: Feng
authors.forename: B P-Y
authors.initials: BP
authors.lastname: Lau
authors.forename: T
authors.initials: T
authors.lastname: Zhao
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004852:Epoxy Compounds / Q000032:analysis*; D004952:Esters / Q000032:analysis*; D005227:Fatty Acids / Q000032:analysis*; D005502:Food; D005504:Food Analysis / Q000379:methods*; D000069463:Olive Oil; D000073878:Palm Oil; D010938:Plant Oils / Q000737:chemistry; D020005:Propanols / Q000032:analysis*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D004852:Epoxy Compounds; D004952:Esters; D005227:Fatty Acids; D000069463:Olive Oil; D010938:Plant Oils; D020005:Propanols; D000073878:Palm Oil; C004312:glycidol