Liquid chromatographic determination of phenol, thymol and carvacrol in honey using fluorimetric detection

A comparison is made between the use of a silica-based monolithic column and a RP-AmideC16 column for the separation of phenol, thymol and carvacrol using reversed-phase liquid chromatography. The best results concerning total analysis time and sensitivity were obtained using the monolithic column. Detection was optimized using a fluorimetric detector which allowed better detection limits that those obtained with a photo-diode array spectrophotometer. Gradient elution with acetonitrile–water mixtures as mobile phases permitted good separation of the phenols. Identification of the peaks was based on their retention characteristics, varying the flow-rate, nature and composition of the mobile phase as well as the nature of the stationary phase, and using the fluorimetric detector to continuously measure the spectrum when the solute passed through the flow cell. Linearity, precision, recovery and sensitivity were satisfactory. The procedure was applied to the analysis of phenol, thymol and carvacrol in honey of different types. The extraction process was very simple, only involving dissolution of honey with water. Detection limits in the honey samples using the proposed procedure were between 1 and 4 ng g−1.