Simultaneous determination of 68 antimicrobial compounds in pigs oral fluid by ultra-high performance liquid chromatography-tandem mass spectrometry.

Improper use of antimicrobials in veterinary medicine can lead to residues in food of animal origin. Post-mortem monitoring of antibiotics in animal products is carried out as part of official EU programmes on food safety and consumer health. Oral fluid testing is a promising surveillance method to monitor appropriate treatment in pigs and to avoid residues in edible tissues. Oral fluid analysis can be implemented in an antibiotic residue control programme, thus preventing economic losses due to meat disposal as a result of drug detection in tissues after the withdrawal period. An analytical method was developed for the analysis of 68 compounds from 12 groups (penicillins, cephalosporins, sulfonamides, macrolides, fluoroquinolones, tetracyclines, aminoglycosides, pleuromutilins, diaminopyrimidines, lincosamides, polypeptides and sulfones) in pig oral fluid. Extraction of antibacterials was performed with 0.5 % formic acid. Analyses were carried out by ultra-high performance liquid chromatography with triple quadrupole mass spectrometry (UHPLC-MS/MS) detection. The chromatographic separation was achieved on a Zorbax analytical column (2.1 × 50 mm) with a mobile phase consisting of acetonitrile and heptafluorobutyric acid (HFBA). The total run time was 7 min. The method was validated as a confirmatory method according to the Commission Implementing Regulation (EU) 2021/808. The reliability of the method was verified by testing real samples from pig farms.