Analysis of phenolic compounds in extra virgin olive oil by using reversed-phase capillary electrochromatography

In this work, the simultaneous separation of ten phenolic compounds (protocatechuic, p-coumaric, o-coumaric, vanillic, ferulic, caffeic, syringic acids, hydroxytyrosol, tyrosol and oleuropein) in extra virgin olive oils (EVOOs) by isocratic RP CEC is proposed. A CEC method was optimized in order to completely resolve all the analyzed compounds by studying several experimental parameters. The influence of the stationary phase type (C(18) and C(8) modified silica gel), buffer concentration and pH as well as the organic modifier content of the mobile phase on retention factors, selectivity and efficiency were evaluated in details. A capillary column packed with Cogent bidentate C(18) particles for 23 cm and a mobile phase composed by 100 mM ammonium formate buffer pH 3/H(2)O/ACN (5:65:30 v/v/v) allowed the baseline resolution of the compounds under study in less than 35 min setting the applied voltage and temperature at 22 kV and 20 degrees C, respectively. A study, evaluating the intra- and interday precision as well as LOD and LOQ and method linearity was developed in accordance with the analytical procedures for method validation. LODs were in the range of 0.015-2.5 microg/mL, while calibration curves showed a good linearity (r(2) >0.997). The CEC method was applied to the separation and determination of these compounds in EVOO samples after a suitable liquid-liquid extraction procedure. The mean recovery values of the studied compounds ranged between 87 and 99%.