Determination of Carvacrol and Thymol in Honey by Using a Simple and Efficient Headspace-Gas Chromatography-Mass Spectrometry Method

A novel method has been proposed to determine residues of thymol and carvacrol in honey, by means of a headspace coupled to a gas chromatography-mass spectrometer. No sample treatment was required, since the samples were injected directly after selection of the optimal headspace operating conditions, in this case, an equilibration time of 7 min and temperatures of 150 °C, 170 °C, or 175 °C for the oven, loop, and transfer line, respectively. The chromatographic conditions were also optimized, with a ZB-WAX (60 m × 0.25 mm × 25 μm) column, the helium carrier gas at a flow rate of 1.1 mL/min, and a temperature program allowing baseline separation of both compounds in under 18 min. Thymol and carvacrol should be quantified in honey samples with matrix-matched standard calibration curves, although samples from rosemary and orange blossom, as well as those of multifloral and heather botanical origins, respectively, can be determined with the same calibration curves. Not only was the proposed method selective, but it was also accurate (relative standard deviation values under 6%) and sensitive (detection and quantification limits lower than 40 μg/kg). Several honey samples were analyzed, and thymol and carvacrol residues were found at low concentrations (quantification limit-97 μg/kg) in some cases.