Expanding Trace Gas Analysis with Bipolar FUSION PTR-TOF Technology

The bipolar FUSION PTR-TOF technology enables rapid switching between multiple reagent ions, significantly broadening the application range without compromising the flexibility of this all-in-one analyzer generation.

No hardware or reactor changes are needed. With push-button simplicity, the bipolar FUSION PTR-TOF sets a new benchmark in trace gas analysis for demanding applications.

Advantages of Multiple Reagent Ions to Characterize Oxidation and Secondary Organic Aerosol Formation

Proton-transfer-reaction mass spectrometry (PTR-MS) is a widely used method for characterizing Secondary Organic Aerosols (SOAs) and their precursors.

Advanced instruments such as the recently introduced FUSION PTR-TOF not only use the proven H₃O⁺ reagent ions for quantitative measurements across a wide range of organic compounds, but also offer additional ionization modes such as NH₄⁺ for soft adduct ionization, enabling the detection of highly oxidized compounds.

Complemented by the NO⁺ and O₂⁺ ionization modes, this instrument supports the detection of the vast majority of both organic and inorganic compounds.

Image Credit: IONICON Analytik

Fast Reagent Ion Switching

A key advantage of the system is its ability to rapidly switch between positive ionization modes in seconds, made possible by the Invion Source. This allows efficient analysis of different compound classes in a short time.

As shown in Figure 1, the instrument can quickly and reproducibly switch between ionization modes (O₂⁺, H₃O⁺, and NH₄⁺) and between E/N settings for H₃O⁺. This flexibility improves both sensitivity and selectivity by tailoring ionization conditions for specific compound types.

Figure 1. Demonstration of the instrument’s capability for fast and reproducible switching between ionization modes (O₂⁺, H₃O⁺, NH₄⁺) and E/N for H₃O⁺, supporting time-resolved multi-mode analysis. Image Credit: IONICON Analytik

Selective Ionization of Acids with CO₃^-

The electronics required for ionization in negative mode with CO₃^– and completely automated switching between positive and negative mode are included in the next-generation FUSION PTR-TOF mass spectrometer.

Organic acids like perfluoroalkyl carboxylic acids and inorganic acids like SO₂, H₂SO₄, and HNO₃ can be detected with great selectivity and sensitivity using CO₃^– ionization.

Products like limononic acid, for example, are identified with great efficiency and little fragmentation because of their ability to facilitate a soft ionization process with low fragmentation.

Figure 2, which compares the resultant ions of several acids following H₃O⁺ and CO₃^– ionization, also makes the latter quite evident. Without requiring any hardware modifications, Figure 3 illustrates how to switch between the CO₃^– and H₃O⁺ ionization modes with a single button press.

Figure 2. Comparison of H₃O⁺ and CO₃⁻ ionization modes, highlighting the enhanced capability of CO₃⁻ ionization for the selective detection of acids with reduced fragmentation. Image Credit: IONICON Analytik

Figure 3. Bipolar switching between CO₃⁻ and H₃O⁺ ionization modes. Image Credit: IONICON Analytik

Conclusion

• CO₃^- is highly selective toward the formed acids
• Compounds like limononic acid are detected effectively with minimal fragmentation
• Sequential use of H₃O⁺, NH₄⁺, NO⁺, and CO₃^- modes enables comprehensive analysis of SOA formation

This information has been sourced, reviewed, and adapted from materials provided by IONICON Analytik.

For more information on this source, please visit IONICON Analytik.