Determination of 62 veterinary drugs in feedingstuffs by novel pressurized liquid extraction methods and LC-MS/MS

A fast and simple method for the determination of 62 veterinary drugs in feedingstuffs was developed, optimized, validated, and applied to real samples. Sample preparation was based on a pressurized liquid extraction method using a hard cap coffee machine, which was compared to a commercial pressurized liquid extraction system. Extraction was performed with diatomaceous earth, acetonitrile (20%), and formic acid (0.1%). A central composite design was used to optimize the composition of the extraction solvent. The extracts were analyzed using two chromatographic modes (reversed phase with C₁₈ and HILIC). Analytical limits were set to 25 (limit of detection) and 75 µg kg^-1 (limit of quantitation). For banned substances, a salting-out step was included, achieving LOQ lower as 1 µg kg^-1 for ractopamine. Other figures of merit such as precision, trueness, decision limit (CC_α), method capability (CC_β), matrix effects, stability, recovery, and measurement uncertainty were also reported for analytical validation. The method was successfully applied to hundreds of real samples demonstrating its fitness-for-purpose for the analysis of sulfonamides, tetracyclines, fluoroquinolones, avermectins, quinolones, beta-agonists, beta-lactams, amphenicols, benzimidazoles, coccidiostats, lincosamides, macrolides, nitrofurans, quinoxalines, melamine, and trimethoprim.