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,syringicacids,hydroxytyrosol,tyrosol and oleuropein) in extra virgin oliveoils(EVOOs) by isocratic RPCEC isproposed. A CECmethod was optimizedin orderto completely resolve all the analyzed compounds by studying several experimental parameters. The influence of the stationary phase type(C18 and C8 modified silica gel),bufferconcentration 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 18 bidentate particles for 23 cm and a mobile phase composed by 100mM ammonium formate buffer pH3/H2O/ACN (5:65:30v/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°C, respectively. A study, evaluating the intra-andinterday 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 rangeof 0.015 - 2.5 microg/mL ,while calibration curves showed a good linearity(r2 higher than 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 87and99%.