Determination of phenols, flavones, and lignans in virgin olive oils by solid-phase extraction and high-performance liquid chromatography with diode array ultraviolet detection

A simple analytical method for the quantitative determination of phenols, f lavones, and lignans in virgin olive oils was developed. The polar fraction was isolated from small amounts of oil sample (2.5 g) by solid-phase extra ction (SPE) using diol-phase cartridges, and the extract was analyzed by re versed-phase HPLC coupled with diode array UV detection. Chromatographic se paration of pinoresinol, cinnamic acid, and 1-acetoxypinoresinol was achiev ed. Repeatability (RSD < 6.5%), recovery (> 90%), and response factors for each identified component were determined. SPE on amino-phase cartridges wa s used for isolating acidic phenols and as an aid for phenol identification . For the first time, 2-(4-hydroxyphenyl)ethyl acetate was detected in oliv e oils. The aldehydic structure of the ligstroside aglycon was confirmed by NMR spectroscopy. The colorimetric determination of total o-diphenolic com pounds by reaction with molybdate was consistent with their HPLC determinat ion. Differences between results obtained by liquid-liquid extraction and S PE were not statistically significant.