Ionic liquids as matrixes for matrix-assisted laser desorption/ionization mass spectrometry

Room-temperature ionic liquids are useful as solvents for organic synthesis , electrochemical studies, and separations. We wished to examine whether th eir high solubalizing power, negligible vapor pressure, and broad liquid te mperature range are advantageous if they are used as matrixes for UV-MALDI. Several different ionic matrixes were synthesized and tested, using peptid es, proteins, and poly(ethylene glycol) (PEG-2000). All ionic liquids teste d have excellent solubilizing properties and vacuum stability compared to o ther commonly used liquid and solid matrixes. However, they varied widely i n their ability to produce analyte gas-phase ions. Certain ionic matrixes, however, produce homogeneous solutions of greater vacuum stability, higher ion peak intensity, and equivalent or lower detection limits than currently used solid matrixes. Clearly, ionic liquids and their more amorphous solid analogues merit further investigation as MALDI matrixes.