Chapter 13: Surface Acoustic Wave Nebulization

A surface acoustic wave (SAW) is an acoustic wave traveling along the surface of a material. In 2010 the first paper describing their use for producing ions for mass spectrometric detection was published, and the phrase “surface acoustic wave nebulization” (SAWN) coined to describe this phenomenon. Ions produced by SAWN are done so either in a continuous electrospray ionization (ESI) like mode or an intermittent manner like matrix-assisted laser desorption ionization (MALDI). In either mode nebulization occurs from a planar surface, with the opportunity to detect either positive or negative ions. Notably, SAWN mass spectra, of chemical compounds such as peptides and proteins that are chemically basic in nature, commonly exhibit a lower average charge-state distribution than ESI produces from the same solution. Importantly, given that no DC voltage is applied to the liquid sample to produce ions, the SAWN-nebulized ions can have lower internal energy than ESI- or MALDI-generated ions.