Quechers methodologies as an alternative to solid phase extraction (SPE) for the determination and characterization of residues of cephalosporins in beef muscle using LC-MS/MS

This work was focused on the comparison of two clean-up methods to be used for the simultaneous determination of seven cephalosporins in cow muscle. In particular, the performance of novel dispersive solid phase extraction (d-SPE) procedures based on QuEChERS methodologies was assessed and compared with conventional SPE. The separation and detection of the analytes using both methods was carried out by LC-MS/MS to reach enough sensitivity to be compatible with the detection of the maximum residue limits (MRL) of cephalosporins as regulated by EU directives. The optimization of the clean-up step relied on experimental design in order to find the most suitable conditions with a reduced number of assays. Besides, multi-objective responses were used to reach an overall compromise in the recovery of all analytes simultaneously. The validation of the two methods was done according to the Directive 2002/657/EC. Linearity, decision limit, detection capability, detection and quantification limits (4-50 mu kg(-1)), precision (RSD less than 15% except for PIR) and recoveries were determined and adequate results with comparable values using QuEChERS and SPE methodologies. LOQ were better for SPE method (0.1-10 mu g kg(-1)) but both methods show LOQ below MRL values. Precision was slightly better for the QuEChERS method, that also presents better recoveries, higher than 85% except for cephalexin. (C) 2012 Elsevier B.V. All rights reserved.