High-throughput determination of phenolic compounds in virgin olive oil using dispersive liquid-liquid microextraction- capillary zone electrophoresis

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.