Analytical strategy for the determination of non-steroidal anti-inflammatory drugs in plasma and improved analytical strategy for the determination of authorised and non-authorised non-steroidal anti-inflammatory drugs in milk by LC-MS/MS

A sensitive and selective method for the determination of six non-steroidal anti-inflammatory drugs (NSAIDs) in bovine plasma was developed. An improved method for the determination of authorised and non-authorised residues of 10 non-steroidal anti-inflammatory drugs in milk was developed. Analytes were separated and acquired by high performance liquid chromatography coupled with an electrospray ionisation tandem mass spectrometer (ESI-MS/MS). Target compounds were acidified in plasma, and plasma and milk samples were extracted with acetonitrile and both extracts were purified on an improved solid phase extraction procedure utilising Evolute^™ ABN cartridges. The accuracy of the methods for milk and plasma was between 73 and 109%. The precision of the method for authorised and non-authorised NSAIDs in milk and plasma expressed as % RSD, for the within lab reproducibility was less than 16%. The % RSD for authorised NSAIDs at their associated MRL(s) in milk was less than 10% for meloxicam, flunixin and tolfenamic acid and was less than 25% for hydroxy flunixin. The methods were validated according to Commission Decision 2002/657/EC.