Determination of epoxidized soybean oil by gas chromatography/single quadrupole and tandem mass spectrometry stable isotope dilution assay

PVC lids of glass jars often contain epoxidized soybean oil (ESBO), able to migrate and contaminate food. To establish a stable isotope dilution assay (SIDA), the 13 C 18 ‐labelled internal standard ethyl 9,10,12,13‐diepoxyoctadecanoate ( 13 C(18:2E)Et) was synthesized, providing after sample preparation the same retention time as methyl 9,10,12,13‐diepoxyoctadecanoate ((18:2E)Me), commonly used as a marker for ESBO in gas chromatographic (GC) analysis. For eleven different food matrices, the GC capillary columns VF‐17ms, DB1701 and DB1 were tested with single quadrupole (GC/MS) as well as tandem mass spectrometric detection (GC/MS/MS). Overall, the VF‐17ms column coupled with MS/MS detection showed the best results in terms of separation and sensitivity. The method validation for the matrix spiked olive oil resulted in a limit of detection (LOD) of 5 mg kg −1 , a limit of quantification (LOQ) of 11 mg kg −1 , a mean recovery (n = 5, c = 106.5 mg kg −1 ) of 99.7 ± 5.5%, with a repeatability (within‐run precision) of 6.0%. By means of GC/MS an LOQ of 21 mg kg −1 and a mean recovery (n = 5, c = 106.5 mg kg −1 ) of 103.3 ± 0.8% with a repeatability of 0.9% were determined. Copyright © 2007 John Wiley & Sons, Ltd.