Liquid Chromatographic Determination of Resveratrol and Piceid Isomers in Honey

In this work, a liquid chromatography method with diode array and fluorescence detection and electrospray ionization mass spectrometry (LC-DAD-FLD and LC-ESI-MS) has been developed for the determination of residues of resveratrol in all its forms (free isomers and glycosylates) in honey. This procedure involves a solid-phase extraction on polymeric cartridges for the isolation of trans/cis-isomers of resveratrol and piceid from diluted honey samples. Chromatographic separation of the analytes was performed in isocratic mode on a C18 column (150 mm × 4.6 mm i.d., 5 μm) operated at 30 °C. The mobile phase consisted of a mixture of water with 1% formic acid and acetonitrile (75/25, v/v), and the flow rate was set at 1.0 mL/min. Average analyte recoveries were from 71% to 113% in replica sets of fortified honey samples. The detection limits when using LC-DAD-FLD were between 40 and 120 μg/kg, meanwhile for LC-ESI-MS were between 1.4 and 14.6 μg/kg. The proposed method was applied to the analysis of honey samples collected from treated beehives in experimental apiaries after a preliminary field trial, and they were not found any residues over the detection limits of the studied compounds.