Flexible Microtube Plasma (FμTP) as an Embedded Ionization Source for a Microchip Mass Spectrometer Interface

Area of Science:

• Analytical Chemistry
• Plasma Physics
• Spectrometry

Background:

• Dielectric barrier discharges are established soft ionization sources for mass spectrometry and ion mobility spectrometry.
• Miniaturization and electrode design have driven advancements in plasma-based analytical techniques.

Purpose of the Study:

• To introduce and evaluate a new flexible microtube plasma (FμTP) discharge design for soft ionization.
• To compare the performance of FμTP against existing ionization sources like DBDI and LTP.

Main Methods:

• Development of a robust, small-footprint FμTP discharge with an electrode integrated into a fused silica capillary.
• Coupling FμTP with gas chromatography/mass spectrometry (GC/MS) for performance evaluation.
• Testing with perfluoroalkanes at low concentrations and headspace analysis of diisopropyl methylphosphonate.

Main Results:

• FμTP demonstrates significantly improved sensitivity, ionization efficiency, and limit of detection compared to DBDI and LTP.
• Negative ion mode showed a >3-fold improvement over DBDI and an 8-fold improvement over LTP in limit of detection.
• Positive ion mode analysis exhibited low fragmentation and high stability, outperforming DBDI and LTP.

Conclusions:

• The FμTP design offers major safety benefits, portability, and versatility in gas usage (H2, N2, air, noble gases).
• FμTP represents a significant advancement in soft ionization sources for mass spectrometry, particularly for trace analysis.
• The new discharge design enables low gas flows (<100 mL min⁻¹) and integration into microchip environments.