Reversed-phase high-performance liquid chromatography coupled to ultraviolet and electrospray time-of-flight mass spectrometry on-line detection for the separation of eight tetracyclines in honey samples

Eight antibiotics, chlortetracycline, demeclocycline, doxycycline, methacycline, minocycline, oxytetracycline, tetracycline and rolitetracycline, were separated and quantified in Spanish honey extracts of different floral origin using a commercial RP-C18 HPLC column and two different on-line detectors (diode array and electrospray time-of-flight mass spectrometry (ESI-TOF-MS) systems). Operating a linear gradient at a flow of 2 ml min−1 the HPLC separation of the eight antibiotics was obtained within 10 min with good peak symmetry and an acceptable resolution (2.1) for the critical band pair rolitetracycline and oxytetracycline. Values of the numbers of theoretical plates (N) were comprised between 2328 and 19 448 while the limits of detection in honey were within 0.02–1.03 μg kg−1 in the case of UV detection and 0.05–0.76 μg kg−1 for ESI-TOF-MS detection (operating in negative mode). A recovery study was carried out by preparing some quality control samples at four levels of concentration (10, 25, 50 and 100 μg kg−1) and percentages between 72% and 98% were attained.