A ToF-MS with a highly efficient electrostatic ion guide for characterization of ionic liquid electrospray sources

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Physical Chemistry

Background:

• Time-of-flight (ToF) mass spectrometry requires efficient ion collection for optimal sensitivity.
• Traditional methods often struggle to capture ions emitted over wide angles and energy distributions.

Purpose of the Study:

• To develop and demonstrate a novel electrostatic ion guide for enhanced ion collection in ToF mass spectrometry.
• To improve the detectability and real-time characterization of electrospray ion sources.

Main Methods:

• Designed a 65-cm long electrostatic ion guide with 13 cascaded Einzel lens stages.
• Utilized simulations to predict ion collection efficiency based on emission angle and energy spread.
• Experimentally validated the ion guide with electrospray ionization of ionic liquids using tungsten needle and microfabricated silicon capillary emitters.

Main Results:

• Simulations predicted 100% charge collection for up to 23° emission half-angle or 30% energy spread.
• Experimental results showed up to 80% charge collection from a tungsten needle electrospray emitter.
• Demonstrated ~30% charge collection from a silicon capillary emitter even with a 40° emission half-angle.

Conclusions:

• The developed electrostatic ion guide significantly enhances charge collection efficiency for ToF mass spectrometry.
• This technology enables improved detectability and real-time characterization of electrospray processes.
• The ion guide is effective across a wide range of emission characteristics and emitter types.