RESUMO
This article reports a simple methodology using dispersive liquid-liquid microextraction combined with CZE. It has been applied for the simultaneous determination of phenolic compounds such as caffeic, gallic, vanillic, syringic, cinnamic, p-coumaric acids and oleuropein, apigenin, luteolin, 3-hydroxytyrosol, and tyrosol, in virgin olive oil (VOO). The optimized extraction conditions for 20 g of VOO were: extractant solvent: 400 µL boric acid 30 mM at pH 9.5; dispersive solvent: 300 µL carbon tetrachloride; vortex: 8 min; centrifugation: 3 min. The composition of the BGE was optimized resulting in the selection of a solution made of 30 mM boric acid at pH 9.5. As a strategy for on-line preconcentration a stacking step was applied, injecting a plug of water before sample injection. The short extraction time, centrifugation and electrophoretic steps allow the selective determination of phenolic compounds in VOO with satisfactory LODs (0.004-0.251 mg/kg), recoveries (89.4-101.0%), and RSD (less than 7.44% in peak area and less than 0.69% in migration time), compatible with the concentration levels present in the samples.