The Vocus PTR-TOF offers unmatched sensitivity and mass resolving power for online detection of VOCs

A proton transfer reaction mass spectrometer (PTR-MS) with sub-ppt limits of detection and mass resolving power up to 15000

Announcing Improved Vocus PTR-TOF Performance and a New Model for Online VOC Monitoring

Advantages of the Vocus PTR-TOF

The Vocus PTR-TOF is a proton transfer reaction mass spectrometer (PTR-MS) for sensitive, real-time detection of volatile organic compounds (VOCs) in industrial, laboratory, and field applications.

  • Ultra-Low Limits of Detection.  High sensitivity and low backgrounds combine to yield sub-ppt VOC limits of detection in seconds
  • Highest Available Mass Resolving Power.  Mass resolving power up to 15000 enables identification of isobaric compounds in complex mixtures
  • Mobile Measurement. Compact, durable architecture brings laboratory-grade performance to vehicle and aircraft-based measurements
  • Adaptable for Your Applications. Work with us to integrate the Vocus PTR-TOF into your existing sampling systems and workflows
  • Intuitive, Powerful Software. Easy-to-use data acquisition interface and Tofware graphical post-processing software for the analysis of high-resolution TOF data
  • Revolutionary PTR Reaction Cell Design.  The proprietary Vocus reaction cell reduces wall losses and focuses ions to give you up to 10x the sensitivity of other commercial PTR-MS. Learn more about the Vocus technology

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Improving PTR-MS without Compromise

The unique Vocus ion molecule reactor (IMR) improves almost all aspects of PTR-MS performance, while maintaining critical specifications and reaction processes that have been established for conventional designs.  

These fundamental aspects of Vocus PTR-TOF performance are key to its fast, ultra-sensitive measurement of trace VOCs.

Select a Vocus Model to Meet Your Measurement Needs

  Sensitivity cps/ppb xylene Limit of Detection (LOD) 1-min / 1-s, xylene Resolving Power at  Specified Sensitivitya M/ΔM Maximum Resolving Powera M/ΔM Size Power Max / Typical
2R 30001 1 ppt  / 10 ppt  10000 15000 160 kg < 0.45 m3 480 x 615 x 1480 mm 600 / 590 W
30001 1 ppt  / 10 ppt 5000 7000  120 kg < 0.35 m3 480 x 615 x 1130 mm 600 / 590 W
Scout 4000  5 ppt, 1 min 3500 4000  120 kg < 0.35 m3 480 x 615 x 1130 mm 600 / 590 W
Elf 500 20 ppt, 1 min 500 750  55 kg < 0.125 m3 380 x 500 x 650 mm 450 /400 W

a. Each model can be operated with higher resolving power at reduced sensitivity.



  • Standby Valve.  Allows servicing of Vocus reaction cell hardware without venting (Models 2R, S, and Scout).
  • Tofware Data Post Processing.
  • Library of Detectable Compounds.
  • Thuner Software. Automatic mass spectrometer tuning software.
  • Touch Screen Control.
  • Shipping Container.  Deployment with no disassembly required.
  • Acquility Data Acquisition and Instrument Control Software.
    • Automated gas calibration and zeroing with programmable cycling
    • Real-time reporting of calibrated concentrations for target compounds
    • Single-click transitions between shutdown, ready, and sleep states



Vocus Reaction Cell and Sampling Inlet

  • Proprietary reagent ion source and ion-molecule reaction cell with axial DC field and RF-focusing.
  • Automated reagent ion switching.
  • Temperature controlled reaction cell, ambient temperature up to 120C.
  • Heated inlet system, up to 180 C.
  Sample Flow Rate 50-500 sccm typical 100 sccm
  Operating Pressure 0.5 – 5 mbar typical 1-2 mbar
  Axial Gradient Uniform linear field 0-5 V/mm
  Reagent Ions H3O+, NO+,O2+, NH4+

Vocus PTR-TOF Publications


  1. Li et al. Overlooked organic vapor emissions from thawing Arctic permafrost. Environ. Res. Lett., 2020. DOI: 10.1088/1748-9326/abb62d
  2. Wang et al. Characteristics of volatile organic compounds (VOCs) with mobile monitoring around the industrial parks in the Yangzte River Delta region of China. Environmental Chemistry, 2020 (in Chinese). DOI: 10.13227/j.hjkx.202007265
  3. Claflin, M. S. et al. An in situ gas chromatograph with automatic detector switching between Vocus PTR-TOF-MS and EI-TOF-MS: Isomer resolved measurements of indoor air. Atmos. Meas. Tech. Discuss. In review 2020. In FocusDOI:10.5194/amt-2020-271
  4. Mehra, A. et al. Evaluation of the chemical composition of gas- and particle-phase products of aromatic oxidation. Atmos. Chem. Phys. 2020DOI: 10.5194/acp-20-9783-2020
  5. Bruderer, T. et al. Detection of Volatile Organic Compounds with Secondary Electrospray Ionization and Proton Transfer Reaction High-Resolution Mass Spectrometry: A Feature Comparison. J. Am. Soc. Mass Spectrom 2020In Focus | DOI: DOI: 10.1021/jasms.0c00059
  6. Li, H. et al. Source identification of atmospheric organic vapors in two European pine forests: Results from Vocus PTR-TOF observations.  Atmospheric Chemistry and Physics In review 2020DOI: 10.5194/acp-2020-648
  7. Wang, Y. et al. Detection of gaseous dimethylamine using Vocus proton-transfer reaction time-of-flight mass spectrometry. Atmospheric Environment 2020. In FocusDOI: 10.1016/j.atmosenv.2020.117875
  8. Wang, Y. et al. Oxygenated products formed from OH-initiated reactions of trimethylbenzene: Autoxidation and accretion. Atmospheric Chemistry and Physics 2020DOI: 10.5194/acp-20-9563-2020
  9. Li, H. et al. Terpenes and their oxidation products in the French Landes forest: insight from Vocus PTR-TOF measurements. Atmospheric Chemistry and Physics 2020. In Focus | DOI: 10.5194/acp-20-1941-2020 


  1. Holzinger, R.; et al. Validity and limitations of simple reaction kinetics to calculate concentrations of organic compounds from ion counts in PTR-MS. Atmos. Meas. Tech. Discuss 2019. DOI: 10.5194/amt-12-6193-2019


  1. Riva, M.; Rantala, P.; Krechmer, J. E.; Peräkylä, O.; Zhang, Y.; Heikkinen, L.; Garmash, O.; Yan, C.; Kulmala, M.; Worsnop, D.; and Ehn, M. Evaluating the performance of five different chemical ionization techniques for detecting gaseous oxygenated organic species. Atmos. Meas. Tech. Discuss 2018.  In Focus | DOI:10.5194/amt-12-2403-2019
  2. Krechmer, J.; Lopez-Hilfiker, F; et al. Evaluation of a New Vocus Reagent-Ion Source and Focusing Ion-Molecule Reactor for use in Proton-Transfer-Reaction Mass Spectrometry. Analytical Chemistry 2018. In FocusDOI: 10.1021/acs.analchem.8b02641

Application Notes

Conference Presentations

Customer Research

TOFWERK Publications


White Papers

Product Information

Background Knowledge About Vocus PTR-TOF

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