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

A sensitive, high performance liquid chromatography/tandem mass spectrometr ic (i.e. mass spectrometry/ mass spectrometry; LC/MS/MS) method with on-lin e extraction and sample clean-up for the screening and confirmation of resi dues of sulfonamides in kidney is described. The sulfonamides are extracted from homogenized kidney with methanol, After centrifugation of the extract , an aliquot of the extract is directly injected on the LC/MS/MS system wit h further extraction and clean-up of the sample on-line. Detection of the a nalytes was achieved by positive electrospray ionization (ESI) followed by multiple reaction monitoring. For each sulfonamide the collisional decompos ition of the protonated molecule to a common, abundant fragment ion was mon itored. The method has been validated for sulfadimethoxine, sulfaquinoxalin e, sulfamethazine, sulfamerazine, sulfathiazole, sulfamethoxazole, sulfadia zine and sulfapyridine, Calibration curves resulting from spiked blank kidn ey samples at the 10-200 mug/kg level showed good linear correlation, At th e level of 50, 100 and 200 mug/kg both within- and between-day precision, a s measured by relative standard deviation (MSD), were less than 16%, The li mits of detection (LODs) ranged from 5 to 13.5 mug/kg. The recoveries range d from 78 to 82%, The procedure provides a rapid, reliable and sensitive me thod for the determination of residues of sulfonamides in bovine kidney. Th e advantage of this method over existing methods is its decreased sample pr eparation and analysis time, which makes the method more suitable for routi ne analysis. Copyright (C) 2000 John Wiley & Sons, Ltd.