Portable proton transfer reaction ion trap mass spectrometer with selectable buffer gas.

Area of Science:

• Analytical Chemistry
• Instrument Development

Background:

• Proton Transfer Reaction Mass Spectrometry (PTR-MS) is crucial for detecting volatile organic compounds (VOCs).
• Conventional PTR-MS devices are bulky, limiting real-time, on-site applications.
• There is a need for portable, sensitive instruments for field analysis.

Purpose of the Study:

• To develop a miniaturized PTR-MS instrument for on-site VOC analysis.
• To evaluate the performance of the miniaturized PTR-MS using different buffer gases.
• To assess the instrument's sensitivity, resolution, and detection limits.

Main Methods:

• Development of a portable PTR-MS based on a portable ion trap mass spectrometer.
• Utilized a small hollow-cathode discharge for ion generation and a compact ion funnel drift tube.
• Investigated performance using helium and nitrogen as buffer gases, analyzing mass resolution, ion fragmentation, and sensitivity.

Main Results:

• The miniaturized PTR-MS weighs 25 kg.
• Helium buffer gas doubled mass resolution and increased ion fragmentation by 17x compared to nitrogen.
• Achieved limits of detection of 1 ppbv for acetone, 0.5 ppbv for benzene, and 0.1 ppbv for toluene.
• Established linear calibration curves over two orders of magnitude concentration range.

Conclusions:

• The developed miniaturized PTR-MS is suitable for rapid, on-site VOC analysis.
• Helium buffer gas significantly enhances instrument performance.
• The portable instrument demonstrates high sensitivity and potential for environmental and industrial applications.