Multi-residue determination of non-steroidal anti-inflammatory drug residues in animal serum and plasma by HPLC and photo-diode array detection

The European Union regulated the use of non-steroidal antiinflammatory drugs (NSAIDs) in animal production and set the official analytical controls to detect their residues in plasma, serum, and milk within the frame of national monitoring programs in each member state. In this work, a multi-residue reversed-phase high-performance liquid chromatography with diode array detector (DAD) method is described for the simultaneous determination of 13 NSAIDs in serum and plasma of farm animals. Chromatographic separation by a C12 stationary phase column with a linear gradient is able to resolve all the compounds considered: salicylic acid, ketoprofen, flurbiprofen, phenylbutazone and its metabolite (oxyphenbutazone), carprofen, ibuprofen, naproxen, niflumic acid, suxibutazone, diclofenac, mefenamic acid, and tolfenamic acid. These compounds are chosen as the most representative of the different NSAID chemical sub-classes. The DAD analysis allows the confirmation of all drugs on the basis of their own UV-vis spectrum, according to the requirements of the European Council Decision 2002/657/EC. Moreover, the method is in-house validated, evaluating mean recoveries, specificity, repeatability, and within-laboratory reproducibility as the performance parameters required by the Decision. The results of this study indicate the method is specific and repeatable, with the mean percentage recoveries of the drugs ranging between 72.5% and 104.5%. Only salicylic acid has poor recovery, with results ranging between 36.3% and 54.9%.