Desorption ionization of biomolecules on metals.

Direct desorption ionization of various types of biomolecules on metal substrates without the need of matrices was observed by a time-of-flight mass spectrometer. It provides a new convenient method for detection of small biomolecules without the confusion of ion peaks from matrix compounds. Simple commercial Al foil can be used as the substrate to obtain mass spectra of biomolecules without the need of an etching process to produce a porous surface such as with direct ionization on silicon (DIOS). The desorption and ionization mechanism is also discussed.