Development of an Atmospheric-Pressure Photoionization Source for VOC Detection With a Miniature High-Pressure Mass...

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Environmental Science

Background:

• Volatile organic compounds (VOCs) require sensitive, selective, and portable quantification methods.
• Miniature mass spectrometers offer potential for on-site analysis but require optimized ionization sources.

Purpose of the Study:

• To develop and optimize an atmospheric pressure photoionization (APPI) source for a miniature high-pressure mass spectrometer (MX908).
• To achieve sensitive, selective, targeted, and portable VOC quantification.

Main Methods:

• Designed and constructed a custom 3D-printed apparatus housing a VUV lamp for the APPI source.
• Investigated and optimized parameters including pressure, axial RF voltage, aperture voltage, and humidity using m-xylene as a standard.
• Tested the instrument's performance with ambient air as the buffer gas.

Main Results:

• The developed APPI source demonstrated effective VOC ionization for the MX908 mass spectrometer.
• Optimized operating conditions were found at 0.8 Torr with ambient air.
• The instrument exhibited excellent linearity (25–500 ppbV) for benzene, toluene, ethylbenzene, and m-xylene.

Conclusions:

• The integrated APPI source provides a sensitive and selective method for portable VOC analysis.
• The system achieves reliable quantification without the need for preconcentration, enhancing field applicability.
• This advancement supports targeted environmental monitoring and industrial hygiene applications.