Surface Acoustic Wave Nebulization as a Mass Spectrometry Ionization Source, Characterization and Application

Abstract

This dissertation describes a novel method to generate ions for mass spectrometers that simplifies the operation and decreases the internal energy distribution of ions. The surface acoustic wave nebulization (SAWN) is a nebulization method generating both positive and negative ions from liquid phase. We have validated this method by successfully ionizing protein, peptide, lipid and other small molecules. The measured internal energy distribution of SAWN is lower compare to electrospray ionization (ESI). To improve the SAWN performance, a standing wave SAWN chip was designed and fabricated. The droplet size of standing wave SAWN was measured and is in general smaller than progressive wave SAWN. The standing wave SAWN design enhanced SAWN performance and kept its low internal energy distribution. After the characterization and improvement, we combined SAWN with digital microfluidics (DMF) for sample preparation before MS detection. DMF-SAWN platform was applied to the analysis of phosphorylated protein mixture. Peptides from all three proteins of the mixture were identified with DMF-SAWN.