Non-vacuum field desorption ion source implemented under super-atmospheric pressure

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Ionization Techniques

Background:

• Standard field desorption (FD) ionization requires high vacuum conditions, limiting its application.
• Developing alternative ionization methods that operate outside high vacuum is crucial for broader accessibility.

Purpose of the Study:

• To demonstrate non-vacuum field desorption (FD) ionization under super-atmospheric pressure.
• To couple this novel ion source with a commercial linear ion trap mass spectrometer.
• To analyze non-volatile compounds, including polar neutrals, organic salts, and ionic liquids.

Main Methods:

• Utilized untreated tungsten wires as field desorption emitters in a super-atmospheric pressure environment (6 bars).
• Employed a high voltage to the emitter, enabled by the dielectric strength of the working gas at elevated pressure.
• Heated samples deposited on the emitter via direct current, observing liquid sample layer protrusion under electric fields.

Main Results:

• Successfully implemented non-vacuum field desorption (FD) ionization at 6 bar.
• Observed characteristic conical protrusion of liquefied samples, similar to vacuum FD.
• Demonstrated the capability to desorb and analyze polar neutral compounds, organic salts, and ionic liquids.

Conclusions:

• Non-vacuum field desorption (FD) is feasible at super-atmospheric pressures.
• This method simplifies instrumentation by eliminating the need for high vacuum.
• The developed ion source broadens the scope of FD-MS for analyzing diverse non-volatile analytes.