RESUMO
An elegant preconcentration method assumed sorption of polar analytes from complex non-polar matrices on a rotating disk based on hydrophilic deep eutectic solvent formation is presented for the first time. The surface of poly(vinylidene fluoride-co-tetrafluoroethylene) rotating disk was coated with choline chloride acted as a precursor of deep eutectic solvent (hydrogen bond acceptor). The rotating disk was immersed in vegetable oil sample and phenolic compounds (hydrogen bond donors) were efficient separated on the disk during its rotation due to deep eutectic solvent formation. Ability of hydrophilic deep eutectic solvent decomposition in aqueous phase was used for fast analytes elution from the disk surface (2 min). Finally, the obtained aqueous solution of phenolic compounds and choline chloride was analyzed by high-performance liquid chromatography with fluorescence detection. Under optimal conditions, the limits of detection for gallic acid, protocatechuic acid, tyrosol, vanillic acid, p-coumarinic acid, syringaldehyde and thymol were in the range of 10-60 µg L-1. The developed approach allowed to significantly reduce sorption and elution time in comparison with previously reported rotating disk sorptive extraction approaches. The extraction mechanism based on deep eutectic solvent formation provided selective separation of target analytes with absolute extraction recovery in the range of 66-87%.
RESUMO
A novel approach for effective sample pretreatment of food was developed. This approach was based on in situ deep eutectic mixtures formation between analytes (hydrogen bond donors) and choline chloride (a hydrogen bond acceptor) supported in a hydrophilic porous membrane. By this action, the analytes were extracted and retained into the hydrophilic porous membrane. Finally, the hydrophilic porous membrane containing the analytes was transferred into an aqueous phase and back-extraction occurred due to deep eutectic mixture decomposition in the aqueous phase. The developed approach was applied to the HPLC-FLD determination of phenols (phenol, o-cresol, p-cresol, eugenol, isoeugenol and guaiacol) in smoked food samples. The limits of detection, calculated from a blank test based on 3σ, were 0.3 µg kg-1 for phenol, o-cresol, p-cresol; 0.6 µg kg-1 for eugenol, isoeugenol; and 1 µg kg-1 for guaiacol.
