Insights into the Analysis of Phenolic Secoiridoids in Extra Virgin Olive Oil

Extra virgin olive oils (EVOOs) containing more than 5 mg/20 g tyrosol, hydroxytyrosol, and their secoiridoids can be recognized by health claims related to the protection of blood lipids from oxidative stress. Therefore, a reliable, accurate, and standardized analytical procedure is needed to determine these markers of EVOO quality. In order to overcome the limitations of current methods, a detailed investigation of sample preparation and chromatographic conditions was performed by UHPLC-UV-HRMS. The use of a C18 fused-core column and nonacidified gradient elution provided single, sharp peaks for oleocanthal and oleacein, allowing their reliable quantitation in UV profiles. Positive- and negative-UHPLC-HRMS/MS characterization of methanolic extracts revealed the presence of dimethyl acetal, methyl hemiacetal, and monohydrate derivatives of all secoiridoids. These artifacts were formed in aqueous methanol, which is usually employed to extract and analyze EVOO phenols, making the HPLC profiles more complex...