Ultrahigh Sensitivity PTR-MS Instrument with a Well-Defined Ion Chemistry

Area of Science:

• Environmental Science
• Analytical Chemistry
• Atmospheric Chemistry

Background:

• Proton-transfer-reaction mass spectrometry (PTR-MS) is a key technique for measuring airborne organic trace gases, relying on predictable ionization efficiency for quantification.
• Recent advancements in ultrahigh sensitivity chemical ionization mass spectrometry (CIMS) have sometimes compromised this crucial unit ionization efficiency.
• There is a need for highly sensitive instruments that retain the quantitative advantages of traditional PTR-MS.

Purpose of the Study:

• To develop a novel ultrasensitive PTR-MS instrument, the FUSION PTR-TOF 10k.
• To ensure the new instrument maintains the universal unit response characteristic of conventional PTR-MS.
• To demonstrate the instrument's capability for sensitive detection of organic trace gases in ambient air.

Main Methods:

• Development of the FUSION ion-molecule reactor, utilizing a static longitudinal electric field and a focusing transversal radiofrequency (RF) field.
• Integration of an improved ion source allowing rapid switching between multiple reagent ions (H₃O⁺, O₂⁺, NO⁺, NH₄⁺).
• Employment of an advanced time-of-flight mass spectrometer with high mass resolution (10000–15000).

Main Results:

• The FUSION PTR-TOF 10k instrument demonstrates universal unit response, similar to traditional PTR-MS analyzers.
• Achieved sensitivities up to 80000 counts per second per part-per-billion by volume (cps ppbV⁻¹).
• Demonstrated detection limits as low as 0.5 parts per trillion by volume (pptV) for 1-second measurements, exemplified by naphthalene detection in ambient air.

Conclusions:

• The FUSION PTR-TOF 10k successfully combines ultrasensitivity with the quantitative reliability of traditional PTR-MS.
• This novel instrument enables highly sensitive, real-time monitoring of organic trace gases at sub-pptV levels.
• The technology holds significant potential for atmospheric chemistry research and environmental monitoring applications.