Chapter 15: Electrospray Laser Desorption Ionization Mass Spectrometry

Electrospray laser desorption ionization mass spectrometry (ELDI/MS), an ambient mass spectrometric technique that combines laser desorption with postionization via electrospray, was developed to rapidly characterize analytes ranging from small organic to large biomolecules. The technique requires essentially no sample pretreatment. The analytes are desorbed through pulsed laser irradiation in the absences of organic matrices like those used in matrix-assisted laser desorption ionization (MALDI). The desorbed molecules subsequently enter an electrospray plume and are postionized through reactions with charged solvent species such as protons, cluster solvent ions, and charged droplets (also termed as species produced from an acidic methanol electrospray solution). This chapter provides a full-scale review of the ELDI technique including its development, underlying principles of operation, ionization mechanism, unique features, related techniques, and applications.