Use of Capillary Zone Electrophoresis to Study the Phenolic Fraction Present in Extra-virgin Olive Oil. Comparison among the Oils Belonging to two P.O.D

We have devised a capillary electrophoretic method for the simple, rapid and simultaneous characterization and quantification of the polyphenolic fraction of extra-virgin olive oil. The capillary-zone electrophoresis (CZE) analyses were carried out in a capillary with 50 μm i.d. and a total length of 47 cm (40 cm to the detector) with a buffer solution containing 45 mM sodium tetraborate pH 9.3, the applied voltage was 28 kV, the injection time was 8 s (hydrodynamic injection), the separations were performed at a temperature of 22ºC and the detection was carried out by ultraviolet (UV) absorption at 200, 240, 280 and 330 nm. This method permits the determination of simple phenols, lignans, complex phenols (secoiridoid derivatives), phenolic acids and flavonoids in the SPE-Diol extracts from extravirgin olive oil in less than 6 min. To our knowledge this is the first study to show the identification of flavonoids and several isomeric forms of secoiridoid compounds in extravirgin olive oil by using CZE. To demonstrate the usefulness of the present method, we have analized ten samples of a spanish P.O.D. (Protected Origin Denomination) and other ten samples belonging to an italian P.O.D. (n=5). In this way, it was possible to compare the phenolic profiles of the oils of different zones of the same P.O.D. and also the phenolic profiles of spanish and italian extravirgin olive oils. The italian oils were richer in terms of lignans, whilst the spanish oils had higher concentrations of secoiridoid compounds.