Ambient Pressure Inverse Ion Mobility Spectrometry Coupled to Mass Spectrometry.

Area of Science:

• Analytical Chemistry
• Physical Chemistry

Background:

• Ambient pressure drift tube ion mobility mass spectrometry (DT-IMMS) offers high resolution but suffers from low duty cycles and ion gate depletion.
• Traditional ion gating methods (Bradbury-Nielsen, Tyndall-Gate) discriminate against low mobility ions, reducing overall sensitivity.

Purpose of the Study:

• To introduce and evaluate a novel inverse ion mobility spectrometry method coupled to time-of-flight mass spectrometry.
• To improve sensitivity and minimize ion gate depletion effects in ambient pressure ion mobility measurements.

Main Methods:

• Coupling inverse ion mobility spectrometry with time-of-flight mass spectrometry.
• Comparing performance (sensitivity, resolving power, ion discrimination) against normal mode DT-IMMS using tetraalkylammonium standards.

Main Results:

• Achieved near 99% duty cycle, a >2 order of magnitude improvement over typical <1% duty cycles.
• Demonstrated significantly increased ion throughput across a broad range of mobilities with minimal loss in resolving power.
• Reduced mobility-based discrimination, particularly for low mobility molecules.

Conclusions:

• Inverse ion mobility spectrometry coupled to mass spectrometry enhances sensitivity and minimizes ion gate depletion.
• The improved duty cycle and reduced discrimination make this method highly advantageous for analyzing diverse analytes.
• Further optimization of the ionization source stability is recommended for optimal performance in inverse mode.