In-vial liquid–liquid microextraction-capillary electrophoresis method for the determination of phenolic acids in vegetable oils
2012
Bakar, Nur Bahiyah Abu | Makahleh, Ahmad | Saad, Bahruddin
An in-vial liquid–liquid microextraction method was developed for the selective extraction of the phenolic acids (caffeic, gallic, cinnamic, ferulic, chlorogenic, syringic, vanillic, benzoic, p-hydroxybenzoic, 2,4-dihydroxybenzoic, o-coumaric, m-coumaric and p-coumaric) in vegetable oil samples. The optimised extraction conditions for 20g sample were: volume of diluent (n-hexane), 2mL; extractant, methanol: 5mM sodium hydroxide (60:40; v/v); volume of extractant, 300μL (twice); vortex, 1min; centrifugation, 5min. Recoveries for the studied phenolic acids were 80.1–119.5%. The simultaneous determination of the phenolic acid extracts was investigated by capillary electrophoresis (CE). Separations were carried out on a bare fused-silica capillary (50μm i.d.×40cm length) involving 25mM sodium tetraborate (pH 9.15) and 5% methanol as CE background electrolyte in the normal polarity mode, voltage of 30kV, temperature of 25°C, injection time of 4s (50mbar) and electropherograms were recorded at 200nm. The phenolic acids were successfully separated in less than 10min. The validated in-vial LLME-CE method was applied to the determination of phenolic acids in vegetable oil samples (extra virgin olive oil, virgin olive oil, pure olive oil, walnut oil and grapeseed oil). The developed method shows significant advantages over the current methods as lengthy evaporation step is not required.
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