Multi-residue determination of anti-inflammatory analgesics in sera by liquid chromatography--mass spectrometry

Non-steroidal anti-inflammatories (NSAIDs) are analgesic, antipyretic, and, as their name implies, anti-inflammatory drugs, which are widely used for the treatment of a variety of human and veterinary disease conditions in which control of pain and inflammation is desired. Acetaminophen (ACE) is a common over-the-counter analgesic. Detection of a variety of widely used NSAIDs and ACE in fluid and tissue samples is an important diagnostic tool. A sensitive and selective analytical method has been developed for simultaneous screening of 12 NSAIDs and ACE by liquid chromatography-mass spectrometry with an atmospheric pressure chemical ionization interface set to operate in the negative ion mode of MS. Following sample preparation, all analytes were separated on a C18-reversed-phase column with a gradient elution of acetonitrile and acetic acid. Full-scan mass spectral fragmentation profiles were established for each analyte and individual extracted ion chromatograms were used for quantitation. Linearity of detection was observed over the 0.05-25.0 microg/mL range of standard concentrations. The instrument limits of detection (LOD), based on an individual analyte quantitation ions, fell between 0.05 and 1.0 microg/mL for all compounds. The matrix LODs were determined to be 0.05 microg/mL for phenylbutazone (m/z 307); 0.1 microg/mL for indomethacin (m/z 312), flunixin (m/z 295), and piroxicam (m/z 330); 0.5 microg/mL for ACE (m/z 150), diclofenac (m/z 250), ketoprofen (m/z 209), and mefenamic acid (m/z 240); 1.0 microg/mL for oxyphenbutazone (m/z 323); 5.0 microg/mL for ibuprofen (m/z 205), salicylic acid (m/z 137), and tolmetin (m/z 212); and 10 microg/mL for naproxen (m/z 185).