Multi-drug ultraperformance liquid chromatography/tandem mass spectrometry method to quantify antimicrobials in feeding stuffs at carry-over level.

Carry-over is an undesirable contamination from medicated to non-medicated during the production of feedingstuffs. In 2014 the European Parliament and the Council started working to produce a new regulatory act that will fix tolerable levels of drugs by carry-over in non-target feed to have a harmonized practice to evaluate this contamination by veterinary drugs. We developed a rapid and effective multi-analyte method coupling ultraperformance liquid chromatography to tandem mass spectrometry (UPLC/MS/MS) for the detection of 37 drugs belonging to different classes of antimicrobials (sulfonamides, tetracyclines, macrolides, quinolones, pleuromutilins and streptogramins) in feeds at carry-over levels. The method was in-house validated in the concentration range 0.25-2.0 mg kg-1 , according to the Regulation (UE) 2017/625 requirements and the guideline included in the Commission Decision 2002/657/EC for official methods. The UPLC/MS/MS method allows the determination of the antimicrobials in 15 min, by providing results compliant to the criteria established by the European Commission legislation. All the analytes showed a limit of detection (LOD) in the range 2.0-5.0 μg kg-1 and a limit of quantification (LOQ) at 10.0 μg kg-1 ; oxytetracycline, doxycycline, spiramycin and virginiamycin have a higher LOD and LOQ (15.0 μg kg-1 ; 30.0 μg kg-1 , respectively). Recoveries were satisfactory ranging from 90.4% to 103.1%. The method is characterized by an effective clean-up of all drugs without the use of large sample size and organic solvent extraction.