Optimization of a solid phase extraction method and hydrophilic interaction liquid chromatography coupled to mass spectrometry for the determination of phospholipids in virgin olive oil

Phospholipids belong to a polar lipid class of compounds and are particularly important as constituents of membrane of lipids in several food products. Nevertheless, phospholipids are poorly investigated as minor compounds in olive oil and in literature the phospholipid extraction has been essentially developed by liquid-liquid extraction (LLE). The aim of this work was to compare the effectiveness of a previous LLE extraction method with a direct separation and purification of olive oil phospholipids with two different solid phase extraction (SPE) sorbents (silica and diol). As far we are concerned this is the first application of SPE for the direct extraction of phospholipids in virgin olive oil. Furthermore, the extracts were analyzed by HPLC with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-qTOF-MS) to obtain basic information useful for a possible identification of the single components. To this aim, a new separation method was established using a hydrophilic fused core liquid chromatography column (HILIC). The HILIC chromatography is readily compatible with electrospray ionization and results in higher sensitivity and improved peak shapes. The SPE diol extraction and HPLC-ESI-qTOF-MS methodology have demonstrated to be very useful to determine the phospholipids in not filtered virgin olive oil and also in a veiled virgin olive oil subjected to a glyceridic crystallization due to a temperature decrease. In fact, it could be observed that crystallization caused a significant decrease in the phospholipid fraction.