Determination of ibuprofen, ketoprofen, diclofenac and phenylbutazone in bovine milk by gas chromatography-tandem mass spectrometry

Abstract

A method has been developed to analyse for ibuprofen (IBP), ketoprofen (KPF), diclofenac (DCF) and phenylbutazone (PBZ) residues in bovine milk. Milk samples were extracted with acetonitrile and sample extracts were purified on Isolute™ C₁₈ solid-phase extraction cartridges. Aliquots were analysed by gas chromatography-tandem mass spectrometry (GC-MS/MS). The method was validated in bovine milk, according to the criteria defined in Commission Decision 2002/657/EC. The decision limits (CCα were 0.59, 2.69, 0.90 and 0.70 ng ml⁻¹, respectively, for IBP, KPF, DCF and PBZ, and detection capabilities (CCβ) of 1.01, 4.58, 1.54 and 1.19 ng ml⁻¹, respectively, were obtained. The measurement uncertainty of the method was 17.8%, 80.9%, 28.2% and 20.2% for IBP, KPF, DCF and PBZ, respectively. Fortifying bovine milk samples (n = 18) in three separate assays show the accuracy of the method to be between 104% and 112%. The precision of the method, expressed as relative standard deviations for the within-laboratory reproducibility at the three levels of fortification (5, 7.5 and 10 ng ml⁻¹) was less than 8% for IBP, DCF and PBZ, respectively. Poor precision was obtained for KPF with a relative standard deviation of 28%.

Keywords:

• ibuprofen
• ketoprofen
• diclofenac
• phenylbutazone
• bovine milk
• method validation

Acknowledgements

The authors would like to thank the staff at The State Laboratory, Ireland, and at The Istituto Zooprofilatico Sperimentale del Mezzogiorno, Italy, for their practical assistance.