Simultaneous Determination of Carvacrol and Thymol in Bee Pollen by Using a Simple and Efficient Solvent Extraction Method and Gas Chromatography-mass Spectrometry

A novel method is proposed to determine residues of carvacrol and thymol in bee pollen by means of gas chromatography coupled to mass spectrometry. This is an efficient and simple sample treatment (with average analyte recoveries between 90% and 104%) involving solvent extraction with hexane followed by evaporation. There is no need for any additional clean-up step, as the matrix did not affect determination of mass spectrometry for either compound. The chromatographic conditions are also optimized: a ZB-WAX column is employed, helium is the carrier gas at a flow rate of 1.1 mL/min, and a temperature program is included, allowing baseline separation of both compounds in less than 21 min. The method is fully validated in terms of selectivity, limits of detection and quantification, matrix effect, linearity, precision and trueness. Results show that not only is it selective, but that it also displays a wide linearity range (limit of quantification-1000 μg/kg), good precision (relative standard deviation values lower than 8%) and sensitivity (limits of detection and quantification lower than 15 μg/kg). Finally, several bee pollen samples are analysed, and thymol and carvacrol residues are found at low concentrations (limit of quantification-57 μg/kg) in some cases.