Analytical strategy for the determination of non-steroidal anti-inflammatory drugs in plasma and improved analytical strategy for the determination of authorized and non-authorized 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 authorized and non-authorized 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 authorized and non-authorized NSAIDs in milk and plasma expressed as % RSD, for the within lab reproducibility was less than 16%. The % RSD for authorized 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.