Determination of 45 antibiotic residues in piglet liver by ultra-high-pressure-liquid-chromatography tandem time-of-flight mass spectrometry

Antibiotics may be administered to food-producing animals for therapeutic and prophylactic purposes. The consumption of animal foods containing antibiotic residues can cause direct toxic effects, such as allergic reactions in some hypersensitive individuals, or indirect effects, such as the appearance of bacterial strains that are resistant to the drugs used in both veterinary and human medicine, becoming a worldwide concern. It is essential for consumer food safety, as well as for public health, to monitor antibiotics in foods of animal origin intended for human consumption, particularly in food sourced from piglets since they constitute a highly consumed meat in Portugal. In this study, 21 piglet liver samples were analysed using ultra-high- pressure liquid chromatography-tandem time-of-flight mass spectrometry (UHPLC-ToF-MS) to detect the presence of 45 antibiotics from 7 different therapeutic classes such as tetracyclines, sulfonamides, quinolones, penicillins, macrolides, cephalosporins and trimethoprim. Concerning the lack of regulations regarding the identification and validation criteria for the ToF-MS detection methodology, this study presents a proposed approach for the use of UHPLC-ToF-MS not only for screening but also for confirmatory purposes. Thus, an analytical method was optimized and validated in accordance with Decision 2002/657/EC by evaluating the decision limit (CCα), detection capacity (CCβ), specificity, selectivity, recovery, repeatability and reproducibility. Using the developed method, antibiotic residues (doxycycline, enrofloxacin, oxolinic acid and ciprofloxacin) were determined in 47% of the analysed samples. Nevertheless, all the antibiotics were detected at concentrations below the MRL levels.