On the glucoside analysis: Simultaneous determination of free and esterified steryl glucosides in olive oil. Detailed analysis of standards as compulsory first step

•Olive oil’s free and esterified steryl glucosides can be analysed simultaneously.•Commercial standards of esterified steryl glucosides were analysed by HPLC–MS in detail.•Free sterol composition and steryl glucoside profiles are independent from each other.•Olive oil (esterified) steryl glucoside content is not cultivar-neither quality-dependent. This work covers two important gaps in the field of micronutrient databases: herein we describe a short and easy protocol that allows the analysis of both free and esterified steryl gulcosides in olive oil. By utilising accurate quantitative methods we achieve a better understanding of olive oil composition and health promoting properties. The procedure consists of isolating the fraction of interest through solid phase extraction, and using gas chromatography–flame ionisation detection for both identification and quantification of the derivatised species. Additionally, mass-spectrometry detection has been utilised for confirming the identity of the individual esterified steryl glucosides in some cases. The method’s limit of detection has been set at 0.37mg/kg for each free steryl glucoside and 0.20mg/kg for each esterified steryl glucoside, whereas the recoveries are around 96% and 77%, respectively. Finally, we provide a complete analysis of the commercial standard for esterified steryl glucosides, since such information was not yet available.