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.

The effect of raw materials on thermo‐oxidative stability and glycidyl ester content of palm oil during frying

“…Analysis of GEs was done as described by Becalski et al , with a few modifications. A double SPE procedure was developed as follows.…”

“…Using this system, the following compounds were separated and quantified: oligomers (triacylglycerol polymers (TGP) and triacyclglycerol dimers (TGD), oxidized triacylglycerols (oxTAG), DAG and FFA. 14,15 Composition of glycidyl esters of fatty acids Analysis of GEs was done as described by Becalski et al, 16 with a few modifications. A double SPE procedure was developed as follows.…”

Occurrence of 3-MCPD and glycidyl esters in edible oils in the United States

“…The quality of indirect methodology has improved, and there are now several methods that appear to provide accurate quantitative information for these classes of contaminants (Kuhlmann 2011;Ermacora & Hrncirik 2013). As a response to the lack of reliability of the early indirect methods, direct approaches were developed for GEs (Blumhorst et al 2011;DuBois et al 2011;Firestone 2011;Haines et al 2011;Becalski et al 2012;Hori, Koriyama, et al 2012) and 3-MCPD esters (Haines et al 2011;Dubois et al 2012;Hori, Koriyama, et al 2012;Hori, Matsubara, et al 2012;Moravcova et al 2012;Yamazaki et al 2013) that do not require hydrolysis and analyse the fatty acid esters as they occur in processed oils without any structural modification. However, due to limitations with each of these direct approaches, methods were developed and validated in our laboratory at the USFDA the LC-MS/MS quantitation of intact esters of 3-MCPD and glycidol in edible oils MacMahon, Mazzola, et al 2013).…”

Occurrence of fatty acid esters of 3-MCPD, 2-MCPD and glycidol in infant formula

“…The esters are detected by means of LC-MS, LC-MS/MS, LCToF-MS, GC-MS or LC-high-resolution-MS (Moravcova et al 2012;MacMahon et al 2013b andDubois et al 2011;Haines et al 2011). For glycidyl-esters different direct methods were developed (Dubois et al 2011;Haines et al 2011;Becalski et al 2012;Steenbergen et al 2013) and one direct LC-MS method developed by Masukawa et al (2011) and Shiro et al (2011) was validated in a collaborative trial and adopted by the American Oil Chemists' Society (AOCS) (Blumhorst et al 2013;AOAC 2012). The esterification of different fatty acids with MCPD leads to a large number of possible MCPD fatty acid esters.…”