A Single Multi-class Method for the Determination of Prohibited Veterinary Drugs in Sausage Casings and Meat (Nitrofuran Metabolites, Nitroimidazoles, Chlorpromazine, Dapsone and Chloramphenicol)

Abstract A single liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to target 24 prohibited substances from different classes, including nitrofurans, nitroimidazoles, chloramphenicol, chlorpromazine and dapsone, in casings and meat. Sample preparation involved acid hydrolysis with derivatisation, followed by QuEChERS clean-up and liquid–liquid extraction. The method was validated in accordance with Commission Implementing Regulation (EU) 2021/808 for ovine casings and bovine meat. Additional validation was performed for bovine and porcine casings, as well as poultry, porcine and ovine meat, using a reduced validation design. In casings, chlorpromazine was suitable for screening but could not be reliably used for confirmatory analysis because of occasional deviations in ion ratios. In ovine casings, increased within-laboratory variability (coefficient of variation, CVw > 30%) for four nitroimidazoles (dimetridazole, carnidazole, tinidazole and ternidazole) and dapsone precluded their reliable quantitative determination in confirmatory analysis and therefore limited their use to screening. Precision was generally better in the other casing matrices, with dapsone in bovine casings being an exception. In meat, chlorpromazine was successfully identified without interference, whereas aminoguanidine could not be reliably used as a marker for nitrovin because of its consistent presence in blank meat extracts. Carnidazole showed increased variability under repeatability conditions (CVr > 20%) in porcine meat, while tinidazole did not meet the trueness acceptance criterion (> 120%) in ovine meat.