Hydrogen Plasma-Based Medium Pressure Chemical Ionization Source for GC-TOFMS.

Area of Science:

• Analytical Chemistry
• Mass Spectrometry
• Chromatography

Background:

• Gas chromatography-mass spectrometry (GC-MS) is a powerful analytical technique.
• Chemical ionization (CI) enhances GC-MS sensitivity and selectivity.
• Developing efficient CI sources for high-temperature applications is crucial.

Purpose of the Study:

• To construct, evaluate, and assess the performance of a novel medium-pressure, high-temperature CI source for GC-MS.
• To investigate the generation of reagent ions using a filament-free helical resonator plasma (HRP) ion source.
• To determine the detection limits and selectivity of the GC-CI-TOFMS system with different reagent gases.

Main Methods:

• A medium-pressure (2-13 mbar), high-temperature CI source was constructed and coupled to a time-of-flight (TOF) mass analyzer.
• Reagent ions (H3+) were generated using a filament-free HRP ion source, followed by reaction with nitrogen, isobutane, or methane.
• Gas chromatography effluent was introduced, and limits of detection were determined using an EPA 8270 LCS mix.

Main Results:

• The GC-CI-TOFMS system produced GC-limited Gaussian peak shapes for high boiling point compounds.
• Limits of detection ranged from 0.4-1.2 pg (nitrogen), 0.6-12.6 pg (isobutane), and 2 pg to >25 pg (methane).
• Nitrogen as reagent gas demonstrated superior selectivity, detecting 74 of 78 EPA pollutants, compared to 41 (isobutane) and 62 (methane).

Conclusions:

• The developed high-temperature CI source coupled with GC-TOFMS provides sensitive and selective analysis.
• Nitrogen is an effective reagent gas for comprehensive detection of EPA pollutants in complex mixtures.
• This GC-CI-TOFMS system is well-suited for analyzing challenging high boiling point compounds.