Extractive electrospray ionization mass spectrometry of ionic liquids

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Materials Science

Background:

• Ionic liquids (ILs) are increasingly vital in industry and research.
• Traditional mass spectrometry (MS) methods struggle with IL analysis due to high salt concentrations and viscosity.
• Novel analytical techniques are needed for reliable IL characterization.

Purpose of the Study:

• To evaluate extractive electrospray ionization mass spectrometry (EESI-MS) for direct analysis of room-temperature ionic liquids (RTILs).
• To assess EESI-MS performance regarding sensitivity, dilution requirements, and tolerance to contaminants.
• To explore the potential of EESI-MS for analyzing IL aggregates and facilitating high-throughput screening.

Main Methods:

• Direct analysis of various RTILs, including [Bmim][PF6], [Bmim][BF4], and [BuPy][BF4], using EESI-MS.
• Comparison of EESI-MS spectra with direct infusion electrospray ionization mass spectrometry (ESI-MS) data.
• Investigation of EESI-MS performance with and without sample dilution.

Main Results:

• EESI-MS successfully detected both cationic and anionic IL components with high sensitivity (<10^-7 M) in diluted samples.
• Analysis without dilution allowed direct observation of IL aggregates in the gas phase at over 2 samples per minute.
• EESI-MS demonstrated high tolerance to chemical contamination and a broad concentration range capability.

Conclusions:

• EESI-MS is a powerful technique for the direct, sensitive, and robust analysis of ionic liquids.
• The method overcomes limitations of classical MS for IL characterization.
• EESI-MS shows significant potential for high-throughput analysis in both fundamental research and industrial applications.