A New Analytical Method for the Quantification of Glycidol Fatty Acid Esters in Edible Oils

Abstract

A novel method to quantify glycidol fatty acid esters (GEs), supposed to present as food processing contaminants in edible oils, has been developed in combination with double solid-phase extractions (SPEs) and LC-MS measurements. The analytes were five species of synthetic GEs: glycidol palmitic, stearic, oleic, linoleic and linolenic acid esters. The use of selected ion monitoring in a positive ion mode of atmospheric chemical ionization-MS with a reversed-phase gradient LC provided a limit of quantification of 0.0045-0.012 mg/mL for the standard GEs, which enables the detection of GEs in mg ranges per gram of edible oil. Using the double SPE procedure first in reversed-phase and then in normalphase second, allowed large amounts of co-existing acylglycerols in the oils to be removed, which improved the robustness and stability of the method in sequential runs of LC-MS measurements. When the method was used to quantify GEs in three commercial sources of edible oils, the recovery% ranged from 71.3 to 94.6% (average 79.4%) with a relative standard deviation of 2.9-12.1% for the two oils containing triacylglycerols as major components, and ranged from 90.8 to 105.1% (average 97.2%) with a relative standard deviation of 2.1-12.0% for the other, diacylglycerol-rich oil. Although the accuracy and precision of the method may not be yet sufficient, it is useful for determining trace levels of GEs and will be helpful for the quality control of edible oils.

Comparison of Indirect and Direct Quantification of Glycidol Fatty Acid Ester in Edible Oils

“…By using the direct LC-MS method 5,6 , a summed level of five species of GE in the oils was determined. Thus, as standard materials, reagent grade GS was used for C18:0-GE while other GEs such as C16:0-GE, C18:1-GE, C18:2-GE, and C18:3-GE were synthesized and used 5 .…”

“…Thus, as standard materials, reagent grade GS was used for C18:0-GE while other GEs such as C16:0-GE, C18:1-GE, C18:2-GE, and C18:3-GE were synthesized and used 5 . The GErich extracts of test oils obtained by double SPE treatment were carefully dissolved in methanol/2-propanol 1:1 by vol for LC-MS analysis, which was performed under the absolute same conditions as in prior work 6 .…”

“…The other method is one reported by Masukawa et al, which directly quantifies five species of GE in edible oils with a combination of a double solid-phase extraction SPE and liquid chromatography-mass spectrometry LC-MS . This direct method has been validated in terms of the trueness and precision of the quantitative values produced by a spike and recovery study of GEs using triacylglycerol TAG -and/or diacylglycerol DAG -rich oils 5,6 . In comparing the indirect and direct methods, using the same samples, we noticed that the indirect method produced lower GE level estimates for some oil compositions.…”

Analytical Methods to Evaluate the Quality of Edible Fats and Oils: The JOCS Standard Methods for Analysis of Fats, Oils and Related Materials (2013) and Advanced Methods

“…These esters are quantified by direct and indirect methods. In the JOCS standard methods, glycidyl fatty acid methyl esters are determined by HPLC coupled with mass spectrometry MS 20 .…”

Collaborative Study of an Indirect Enzymatic Method for the Simultaneous Analysis of 3-MCPD, 2-MCPD, and Glycidyl Esters in Edible Oils

“…Gly-Es were also found in diacylglycerol DAG -enriched oils marketed in Japan 8 , which attracted public attention.…”