Atmospheric pressure ionization in a miniature mass spectrometer

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Instrument Development

Background:

• Miniaturization of analytical instruments is crucial for portable and field applications.
• Atmospheric pressure ionization sources offer advantages for analyzing diverse samples.
• Cylindrical ion traps provide versatile mass analysis capabilities.

Purpose of the Study:

• To describe the design and analytical performance of a novel miniature cylindrical ion trap mass spectrometer.
• To demonstrate its capability for analyzing both gas-phase and solution-phase samples.
• To evaluate its potential for trace analysis and enhanced specificity using MS/MS.

Main Methods:

• Development of a custom-built, three-stage differentially pumped vacuum system.
• Integration of home-built ion optics, custom electronics, and LabView control software.
• Utilized atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) with corona discharge and ESI sources.

Main Results:

• Achieved a mass/charge limit of ~450 Th with unit resolution using a 2.5-mm internal radius cylindrical ion trap.
• Demonstrated MS/MS capabilities for increased specificity, exemplified by nitrobenzene analysis.
• Reported limits of detection for methyl salicylate (1.24 ppb) and nitrobenzene (629 pptr); achieved >50% isolation and CID efficiencies.

Conclusions:

• The developed miniature ion trap mass spectrometer is a versatile instrument for trace analysis.
• Its atmospheric pressure interface and MS/MS functionality enhance its applicability for diverse chemical analyses.
• Further optimization is needed to extend the dynamic range beyond the current two orders of magnitude.