Matrix-Free Formation of Gas-Phase Biomolecular Ions by Soft Cluster-Induced Desorption

摘要

Mass spectrometry of biological macromolecules has developed into a key technology for fast routine analysis in biotechnology. A critical issue is the efficient transfer of nonvolatile biomolecules out of their sample solution into the gas phase in combination with their concomitant ionization. Established standard methods are matrix-assisted laser desorption and ionization (MALDI) and electrospray ionization (ESI). MALDI comprises laser desorption of analyte molecules that have been embedded in a matrix that is strongly absorbing at the laser wavelength ; in ESI, the sample solution is directly dispersed into charged nanoscopic droplets by a combination of gas injection and a strong electrostatic field applied to a microcapillary. Alternative methods include massive cluster impact ionization (MCI), secondary ion mass spectrometry (SIMS), and electrospray droplet impact (EDI) in combination with SIMS, which all make use of an impacting charged particle to desorb and ionize the biomolecules. Using a spray of charged droplets, desorption electrospray ionization (DESI) combines the ESI scheme with a soft desorption process and allows for mass spectrometry of biomolecules under ambient conditions.