Furoic and mefenamic acids as new matrices for matrix assisted laser desorption/ionization-(MALDI)-mass spectrometry

Abstract

The present study introduces two novel organic matrices for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of small molecules. The first matrix is “2-amino-4,5-diphenylfuran-3-carboxylic acid” (also called furoic acid, FA) which was synthesized and then characterized by ultraviolet (UV), infrared (FTIR), nuclear magnetic resonance NMR (1H and 13C) and mass spectrometry. The compound has organic semiconductor properties and exhibits intense UV-absorption which is suitable for the UV-MALDI laser (N2 laser, 337nm). The second matrix is mefenamic acid (MA). The two matrices can be successfully applied for various classes of compounds including adenosine-5′-triphosphate (ATP, 0.5µL(10.0nmol)), spectinomycin (spect, 0.5µL(14.0nmol)), glutathione (GSH, 0.5µL(9.0nmol)), sulfamethazole (SMT, 0.5µL(2.0nmol)) and mixture of peptides gramicidin D (GD, 0.5µL (9.0nmol)). The two matrices can effectively absorb the laser energy, resulting in excellent desorption/ionization of small molecules. The new matrices offer a significant enhancement of ionization, less fragmentation, few interferences, nice reproducibility, and excellent stability under vacuum. Theoretical calculations of the physical parameters demonstrated increase in polarizability, molar volume and refractivity than the conventional organic matrices which can effectively enhance the proton transfer reactions between the matrices with the analyte molecules. While the reduction in density, surface tension and index of refraction can enhance homogeneity between the two new matrices with the analytes. Due to the sublimation energy of mefenamic acid is (1.2 times) higher than that of the DHB, it is more stable to be used in the vacuum.