Quantification of phenolic compounds in vegetable oils by mixed-mode solid-phase extraction isotope chemical labeling coupled with UHPLC-MS/MS

In the present work, a rapid, accurate and cost-effective method has been developed for the simultaneous quantification of phenolic compounds in oil using mixed-mode solid-phase extraction (SPE) coupled with chemical labeling UHPLC-MS/MS. Mix-mode SPE weak cation cartridges were selected to enrich and purify phenolic compounds in oil, and hydroxyl moiety was dansylation as stable-isotope internal standard. The major parameters that affected the extraction and chemical labeling efficiency were investigated, and the method was fully validated. The limit of quantifications and the limit of detections were 0.002 µg kg −1  ~ 0.10 µg kg −1 and 0.006 µg kg −1  ~ 0.30 µg kg −1 , respectively. The recoveries were 61.2% ~ 129.3% with intra-day and inter-day precision less than 12%. The results for 38 rapeseed oils revealed that 14 phenolic compounds, including canolol, phenolic acids, phenolic alcohols, tyrosol and vanillin from trace levels to relatively high content.