Ion sampling effects under conditions of total solvent consumption

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Nanotechnology

Background:

• Nanoelectrospray ionization (nESI) is a technique for generating ions from solution for mass spectrometry.
• Optimizing nESI requires understanding ion formation, desolvation, and transfer into vacuum systems.
• Previous studies have focused on lower flow rates or less efficient sampling conditions.

Purpose of the Study:

• To investigate nanoelectrospray properties under conditions of complete liquid vaporization and vacuum system inhalation.
• To determine desolvation requirements, sampling efficiency, and molar response characteristics of various compounds.
• To establish the relationship between ion count rate and analyte mass under high sampling efficiency.

Main Methods:

• Utilized a nanoelectrospray source with gas nebulization for stability.
• Employed a heated laminar flow chamber to improve desolvation and ion production.
• Varied inlet conditions including flow rates (50-500 nL/min), solution compositions, and compound types.
• Adjusted atmosphere-to-vacuum aperture diameters to maximize ion transfer.

Main Results:

• Achieved high sampling efficiencies of 70-85% for favorable compounds under ideal solvent conditions.
• Observed lower efficiencies for aqueous samples.
• Demonstrated that different compound structures yielded varying molar response factors.
• Found a direct proportionality between ion count rate and absolute analyte mass entering the source.

Conclusions:

• Nanoelectrospray can achieve high sampling efficiencies when operating under conditions of complete vaporization and efficient vacuum transfer.
• Understanding compound-specific responses and solvent effects is crucial for quantitative analysis.
• The direct correlation between ion count rate and analyte mass supports the potential for accurate quantification in this high-efficiency regime.