Determination of tetracyclines in bovine kidney by liquid chromatography/tandem mass spectrometry with on-line extraction and clean-up

A novel, sensitive, high performance Liquid chromatography/tandem mass spec trometric (i.e. mass spectrometry/mass spectrometry) method with on-line ex traction and clean-up for the screening and confirmation of residues of tet racyclines in kidney has been developed. After liquid extraction of homogen ised kidney with McIlvain buffer, an aliquot of the extract is directly inj ected on the LC/MS/MS system with further extraction and clean-up of the sa mple on-line. Detection of the analytes was achieved by positive electrospr ay ionization followed by multiple reaction monitoring. For each tetracycli ne the collisional decomposition of the protonated molecule to a unique, ab undant fragment ion was monitored. The method has been validated for tetrac ycline, oxytetracycline, chlortetracycline and doxycycline, Calibration curves resulting from spiked blank kidney samples at the 100-12 00 mu g/kg level showed good linear correlation. At the level of 600 mu g/k g both within- and between-day precision, as measured by relative standard deviation (RSD), were less than 7%, The limits of detection (LODs) for tetr acycline, oxytetracycline, chlortetracycline and doxycyline were 18, 23, 24 and 21 mu g/kg, respectively. The limits of quantification (LOQs) for tetr acycline, oxytetracycline, chlortetracycline and doxycyline were 36, 46, 47 and 42 mu g/kg, respectively. The recoveries ranged from 71 to 91%. The pr ocedure provides a rapid, reliable and sensitive method for the determinati on of residues of tetracyclines in bovine kidney. The advantage of this met hod over existing methods is its decreased sample preparation and analysis time, which makes the method more suitable for routine analysis. Copyright (C) 2000 John Wiley & Sons, Ltd.