A model for solvated ion emission from electrospray droplets.

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Mass Spectrometry

Background:

• Electrospray ionization (ESI) is crucial for analyzing large molecules like proteins.
• Existing models for ion emission from ESI droplets have limitations in predicting energy requirements.
• Understanding ion emission mechanisms is key to optimizing ESI-Mass Spectrometry.

Purpose of the Study:

• To present a refined model for ion emission from electrospray droplets.
• To investigate the energy landscape of ion formation, considering droplet dynamics.
• To bridge the gap between different ion emission mechanisms observed in ESI.

Main Methods:

• Development of a theoretical model incorporating droplet surface distortion.
• Analysis of energy requirements for singly and multiply charged ion emission.
• Comparison of model predictions with established theories like the charge residue model (CRM).

Main Results:

• The model predicts significantly lower energy requirements for ion emission compared to previous models.
• It describes a spectrum of mechanisms, including pure ion evaporation (PIE) for small ions.
• For large ions, a novel mechanism, activated pseudo-Rayleigh ion release (PRIR), is proposed, yielding charge states similar to CRM.

Conclusions:

• Droplet surface distortion is a critical factor in ion emission from ESI.
• The proposed model offers a more comprehensive explanation for ion formation across different ion sizes and charge states.
• Model predictions align qualitatively with experimental observations in electrospray ionization.