Impact desolvation of electrosprayed microdroplets - a new ionization method for mass spectrometry of large biomolecules

Impact desolvation of electrosprayed microdroplets (IDEM) is a new method f or producing gas-phase ions of large biomolecules. Analytes are dissolved i n an electrolyte solution which is electrosprayed in vacuum, producing high ly charged micron and sub-micron sized droplets (microdroplets). These micr odroplets are accelerated through potential differences similar to5 - 10 kV to velocities of several km/s and allowed to impact a target surface. The energetic impacts vaporize the droplets and release desolvated gas-phase io ns of the analyte molecules. Oligonucleotides (2- to 12-mer) and peptides ( bradykinin, neurotensin) yield singly and doubly charged molecular ions wit h no detectable fragmentation. Because the extent of multiple charging is s ignificantly less than in atmospheric pressure electrospray ionization, and the method produces ions largely free of adducts from solutions of high io nic strength, IDEM has some promise as a method for coupling to liquid chro matographic techniques and for mixture analysis. Ions are produced in vacuu m at a flat equipotential surface, potentially allowing efficient ion extra ction. Copyright (C) 2001 John Wiley & Sons, Ltd.