Soft Ionization of Metallo-Mefenamic Using Electrospray Ionization Mass Spectrometry

Detection of mefenamic acid (M, non-steroidal anti-inflammatory drug, NSAIDs) and its metallodrug was investi- gated using electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectroscopy. ESI-MS data (500 µL, 1×10-3 M) revealed high detection sensitivity for the drug and metallodrug. ESI-MS spectra revealed peaks at 242, 580, and 777 Da cor- responding to (M+H)+, (63Cu(M-H)2(H2O)2+H)+, and (56Fe(M-H)3+H)+, respectively. The metal:mefenamic ratios of ESI- MS spectra are in complete agreement with the fluorescence spectroscopy results (1:2 for Cu(II) and 1:3 for Fe(III)). ESI is a soft ionization technique that can be used on labile metallo-mefenamic acids and is promising for the detection of these species in environmental samples and biological fluids.