Positively Charged Water Microdroplets Ionize Surrounding Gas Molecules

Area of Science:

• Analytical Chemistry
• Physical Chemistry

Background:

• Electrospray ionization (ESI) uses high voltage to create charged microdroplets for generating ions.
• A recent claim suggested only negatively charged microdroplets ionize surrounding gases.

Purpose of the Study:

• To investigate the gas-phase ionization capabilities of positively charged microdroplets in electrospray ionization.
• To challenge the notion that only negatively charged microdroplets can ionize neutral molecules.

Main Methods:

• Utilized stabilized nanoelectrospray of deionized water.
• Employed high-resolution mass spectrometry to detect ionization products.

Main Results:

• Demonstrated that positively charged water microdroplets ionize neutral species like oxygen, toluene, and organic vapors.
• Confirmed the generation of ionization products from various neutral molecules in the vicinity of positive microdroplets.

Conclusions:

• Positively charged microdroplets are capable of inducing gas-phase ionization of neutral molecules.
• This ionization process likely involves electron loss from neutral precursors, facilitated by intense electric fields at the microdroplet surface.