Using the IONICON PTR-TOFMS Series to Study the Deposition and Emission of BVOCs

Biogenic emissions are the major source of most volatile organic compounds (VOCs) present in the atmosphere. These biogenic volatile organic compounds (BVOCs) include oxygenated organic compounds such as hexenal, acetic acid, acetone, and methanol, and hydrocarbons such as sesquiterpenes, monoterpenes and isoprene. They have a significant contribution in atmospheric chemistry as well as in the formation of secondary aerosol (SOA) and ozone production.

Proton Transfer Reaction - Mass Spectrometry

Proton transfer reaction (PTR) is suitable for the measurement of BVOCs as well as previously unexpected compounds. Previously, the atmosphere-ecosystem exchange of only very few BVOCs has been studied. With high-time resolution and ultra-fast analysis capabilities, the IONICON PTR-TOFMS series products can perform eddy-covariance measurements for the studies of the active atmosphere-ecosystem exchange of a broad range of BVOCs. This capability helps in gaining more knowledge about the atmospheric VOC budget.

PTR-MS - Trace Gas Analysis in Real-Time

IONICON PTR-MS systems are the most sensitive instruments for real-time monitoring of hundreds of Volatile Organic Compounds (VOCs), such as acetone, acetaldehyde, methanol, ethanol, benzene, toluene, xylene and many others, including some inorganic compounds, present in air.

The ionization by Proton Transfer Reaction (PTR) has several advantages;

  • Very efficient - high sensitivity with LODs < 1 pptv
  • Very soft - with little to no and adjustable fragmentation
  • Does not require pre-separation, such as GC
  • No sample preparation is necessary

Together this allows for trace gas analysis in real-time.

Eddy Covariance Technique

The eddy covariance method, also referred as eddy correlation and eddy flux method, performs measurements and calculations of vertical turbulent fluxes present in the atmosphere. This technique needs highly time resolved 3D wind component measurements.

It is possible to correlate a parallel measurement of VOC concentrations with the vertical wind component for extraction of emission and deposition fluxes. For this purpose, a trace gas analyzer must be capable of quantitatively measuring ultra-low VOC concentrations at a high-time resolution of 10Hz. These prerequisites of eddy covariance flux measurements are perfectly satisfied by the PTR-TOFMS series from IONICON.

IONICON’s PTR-TOFMS Series

IONICON’s PTR-TOFMS Series enables high time resolution measurements faster than 10Hz and can yield quantitative measurements for trace gas concentrations due to its high sensitivity. In each measurement, IONICON PTR-TOF instruments collect the entire spectrum and acquire information about a broad range of existing BVOCs.

In addition, they can separate isobars and perform chemical identification of the compounds of interest, thanks to their high mass resolving power. IONICON PTR-TOFMS technology is already a reliable technique for most scientists involved in the atmospheric research.

IONICON PTR-MS Soft Ionization Technology

The novel IONICON PTR-MS soft ionization technology (Figure 1) ionizes all compounds that have a proton affinity (PA) higher than water through proton transfer from H3O+. Atmospheric air constituents such as carbon dioxide, argon, oxygen, and nitrogen are not detected due to their lower PAs when compared to water. This is a key reason behind the IONICON technology’s low, real-time detection limit for trace compounds. The IONICON PTR-TOFMS features precisely controlled drift tube parameters and ion source, thus enabling absolute quantification of VOC concentrations.

The new IONICON X2 technologies comprise the latest generation of performance tools including the ION-BOOSTER funnel as well as the hexapole ION-GUIDE for the ultimate PTR-TOFMS experience. The ion funnel focuses the ions into the hexapole ion guide which results in nearly lossless transmission of an extremely focused ion beam into the TOF mass spectrometer. This increases the sensitivity dramatically and also improves the instrument’s mass resolving power. The recently launched PTR-TOF 6000 X2 is IONICON’s current flagship model and incorporates the new X2 technologies.

IONICON X2 technologies for PTR-TOFMS performance increase: ION-BOOSTER funnel and hexapole ION-GUIDE

Figure 1. IONICON X2 technologies for PTR-TOFMS performance increase: ION-BOOSTER funnel and hexapole ION-GUIDE

IONICON’s proprietary Selective Reagent Ionization - Mass Spectrometry (SRI/SRI+) technology is available as an option with the IONICON PTR-TOFMS. It features NO+ and O2+ (SRI) or Kr+ (SRI+) as alternative to H3O+ as precursor ions generated in the new ULTRA-PURE ion source (patent pending). The ionization potential of O2+ and Kr+ is higher than H3O+, enabling an IONICON instrument to detect and quantify several key inorganic substances such as SO2, NO2, CO2, CO, CH4, and much more. A large number of isomeric VOCs can be separated and subsequently quantified in real time with the help of NO+ as reagent ions.

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

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

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