Internal energy distributions in desorption electrospray ionization (DESI)

Area of Science:

• Analytical Chemistry
• Mass Spectrometry

Background:

• Desorption electrospray ionization (DESI) is a key technique for analyzing samples.
• Understanding ion formation energetics is crucial for optimizing mass spectrometry methods.

Purpose of the Study:

• To compare the internal energy distributions of ions generated by DESI, electrospray ionization (ESI), and electrosonic spray ionization (ESSI).
• To investigate the influence of experimental parameters on ion fragmentation in DESI and ESSI.

Main Methods:

• Utilized the "survival yield" method to measure ion internal energy distributions.
• Compared ion energetics and fragmentation patterns across DESI, ESI, and ESSI.
• Analyzed the impact of nebulizing gas pressure, solvent flow rate, and sprayer distance on ion survival.

Main Results:

• DESI, ESI, and ESSI yield ions with similar internal energy distributions (mean values of 1.7-1.9 eV).
• Observed comparable trends in ion fragmentation as a function of source parameters for DESI and ESSI.
• Confirmed that DESI involves droplet pick-up followed by ESI-like ion formation.

Conclusions:

• The similar energetics suggest analogous late-stage ion formation processes in DESI, ESI, and ESSI.
• Experimental parameters offer control over the energetics of the DESI ionization process.
• Findings support a "droplet pick-up" mechanism for DESI followed by ESI-like desolvation and ion formation.