Micellar electrokinetic chromatography method for the simultaneous determination of furanic compounds in honey and vegetable oils

A simple micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of 2-furfural (2-F), 3-furfural (3-F), 5-methylfurfural (5-MF), 5-hydroxymethylfurfural (5-HMF), 2-furoic acid (2-FA) and 3-furoic acid (3-FA) in honey and vegetable oils is described. Parameters affecting the separation such as pH, buffer and surfactant concentrations, applied voltage, capillary temperature, injection time and capillary length were studied and optimized. The separation was carried out in normal polarity mode at 20 °C, 22 kV and using hydrodynamic injection (17 s). The separation was achieved in a bare fused-silica capillary (46 cm × 50 μm i.d.) with a background electrolyte of 75 mM phosphoric acid (pH 7.3), containing 200 mM of sodium dodecyl sulphate (SDS). The detection wavelengths were at 200 nm (2-FA and 3-FA) and 280 nm (2-F, 3-F, 5-MF, 5-HMF). The furfurals were well separated in less than 20 min. The method was validated in terms of linearity, limit of detection and quantitation, precision and recoveries. Calibration curves of the six furfurals were well correlated (r(2)>0.991) within the range 1-25 μg mL(-1). Relative standard deviations of intra- and inter-day migration times and corrected peak areas ≤9.96% were achieved. The limit of detection (signal:noise, 3) was 0.33-0.70 μg mL(-1) whereas the limit of quantitation (signal:noise, 10) was 1.00-2.12 μg mL(-1). The method was applied to the determination of furanic compounds in honeys and vegetable oils (palm, walnut, grape seed and rapeseed). The effects of thermal treatment and gamma irradiation on the formation of the furanic compounds in honey were also investigated.