Quantitative Method to measure Glycidol Fatty Acid Esters (GEs) in Edible Oils

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1 101 st AOCS Annual Meeting & Expo Quantitative Method to measure Glycidol Fatty Acid Esters (GEs) in Edible Oils Hiroki Shiro* 1, Yoshinori Masukawa 1, Naoki Kondo 1 and Naoto Kudo 2 1 Tochigi Research Labs, 2 Tokyo Research Labs, Kao corporation Japan May 18, 2010

2 Summary In response to great concerns on contaminants, GEs, in edible oils, we developed a method for quantification of GEs in edible oils (J. Oleo Sci. 58: 81-88, 2010). In this study, the method was improved to overcome the drawbacks. The LC-MS conditions were modified. Then, the conditions were more generalized from specific fast-hplc to common conventional HPLC, and the measurement time was shortened to 5 min from 17 min of original one with a step gradient LC. The pretreatment (double SPE) was improved. Then, the sequential runs became possible under conventional HPLC conditions, and not only liquid but also solid edible oils were applicable. Also, the pretreatment time was shortened. The accuracy of the method improved was demonstrated using three different sources of edible oils.

3 Idea for Solution 1. Use of highly sensitive LC-MS 2. Use of double SPE using reversed-phase and normal-phase TAG DAG MAG Three acyls One hydroxyl Two hydroxyls Difference in hydrophobicity One acyl GE O Trace level Difference in hydrophilicity No hydroxyl Double SPE using reversed-phase and normal-phase in combination with highly sensitive LC-MS would be effective.

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5 Pretreatment LC-MS quantification J. Oleo Sci. 59: (2010) Run: 17 min Total: 40 min 100 mg Edible oil GE-rich fraction Dispersed in acetonitrile Fast HPLC under linear gradient Reversed-phase SPE using acetonitrile Normal-phase SPE using chloroform Single quadruple MS (positive APCI, SIM) Total: half to one day ODS column for UPLC

6 Today s Presentation Our method published in J. Oleo Sci. 59: (2010) Use a specific LC instrument for fast-hplc Take long time to perform LC-MS measurement (17 min) Be limited only to application of liquid edible oils Take long time to do pretreatment Use chloroform that is wanted not to use if possible 1. Change to Conventional HPLC Shorten LC-MS Measurement Time 2. Expand only from Liquid also to Solid edible oils Shorten double SPE Procedure Time Avoid the Use of Chloroform if possible

7 Re-examination of Sample Preparation 1. Ca. 0.1 g of each oil was weighed accurately into and was then dispersed in 4 ml acetonitrile with stirring for 10 min. Not applicable to solid edible oils, because of the insolubilities 2. After centrifugation, the supernatant was applied to the first reversed-phase SPE using a Sep-Pak Vac RC C18 cartridge 500mg. After the supernatant passed through, the cartridge was washed out twice with 2 ml acetonitrile. 3. The acetonitrile solutions combined were evaporated to dryness using a nitrogen stream. Long time to dry up acetonitrile, because of the less volatility 4. The dried residue was dissolved in 2 ml chloroform, and was then applied to a second normal-phase SPE using a Sep-Pak Vac RC Silica cartridge 500mg. After the solution passed through, the cartridge was washed out twice with 2 ml chloroform. The cartridge was further washed out with 2 ml chloroform. Use of large volume of chloroform (8 ml) as an eluent 5. The chloroform solutions combined were dried again using a nitrogen stream. 6. The dried residues were dissolved in 1 ml methanol/2-propanol (1:1 by vol) in the case of TAG-rich oils, and in 10 ml in the case of DAG-rich oil. 7. The resulting solutions were subjected to LC-MS.

8 Conclusion We could improve the original method into a new method that is rapid, stable, more generalized, reproducible, high-sensitive and accurate to quantify GEs not only in liquid but also in solid edible oils, by overcoming the drawbacks. This quantitative method can be expansively generalized to be used as a standard over the world. Changes in the method: -Use of conventional-hplc -Use of a step gradient LC -Use of chloroform/acetone to solve the oils as the 1 st process -Use of methanol in the first reversed-phase SPE -Use of hexane/ethyl acetate in the second normal-phase SPE