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

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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. The instrument combines TOFWERK’s novel Vocus proton transfer reaction cell with our high performance time-of-flight technology to offer you market leading sensitivity and mass resolving power.

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
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
Automated Reagent Ion Switching. Switching between H₃O⁺, NO⁺, O₂⁺ and NH₄⁺expands the breadth of detectable compounds and resolves isomers
Interchangeable Ion Sources. Built on our API-TOF platform, the Vocus PTR-TOF allows you to interchange the Vocus PTR reaction cell with an array of other ion sources.
Adaptable for Your Applications. Work with us to integrate the Vocus PTR-TOF into your existing sampling systems and workflows
Field-Ready Hardware. Compact, durable architecture brings laboratory-grade performance to challenging environments
Intuitive, Powerful Software. Easy-to-use data acquisition interface and Tofware graphical post-processing software for the analysis of high-resolution TOF data

Webinar: Vocus PTR-TOF Real-time VOC Analysis with Market Leading Performance

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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.

Low Product Ion Energies

The RF focusing fields in the Vocus ion molecule reactor improve sensitivity while maintaining product ion energies and recorded branching ratios that are nearly identical to those of traditional drift-tube PTR ion-molecule reactor designs. Read More »

High Purity Reactant Ions

Vocus PTR-TOF mass spectra are dominated by protonated peaks and free of significant contributions from non-PTR reaction and therefore easily interpreted and quantified. Read More »

Simple Calibration

The Vocus PTR-TOF routinely detects a very large number of VOCs, including many for which standards are not available. It is possible to calibrate for all detected compounds with good accuracy based on simple measurements of a small number of VOC standards. Read More »

Ultra-Fast Time Response

The combination of its efficient inlet system, heated reaction cell, and high sensitivity makes the Vocus PTR-TOF the optimum detector for high throughput or highly time resolved measurements of low volatility organic compounds. Read More »

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 Sensitivity^a M/ΔM	Maximum Resolving Power^aM/ΔM	Size	Power Max / Typical
2R	10000	1 ppt / 10 ppt	10000	15000	160 kg < 0.45 m^₃ 480 x 615 x 1480 mm	600 / 590 W
S	10000	1 ppt / 10 ppt	5000	7000	120 kg < 0.35 m^₃ 480 x 615 x 1130 mm	600 / 590 W
M	500	<5 ppt, 1 min	2000	2500	120 kg < 0.35 m^₃ 480 x 615 x 1130 mm	600 / 590 W
Elf	500	20 ppt, 1 min	500	750	55 kg < 0.125 m^₃ 380 x 500 x 650 mm	450 /400 W

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

Sub-ppt limits of detection in seconds Calculated as 3 times the standard deviation of signal with ultra clean air and assuming the sensitivity of BTX.

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⁺

Components

Standard

Standby valve to allow servicing of Vocus reaction cell hardware without venting
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
Tofware data post processing
Library of detectable compounds
Thuner automatic mass spectrometer tuning software
Touch screen control
Shipping container for deployment with no disassembly required

Options

Liquid calibration system (LCS), with dedicated controls in Acquility software
GC or fast-GC, control and method definition with Acquility software
Aerosol inlet, including automated switching between measurements of gas, particle-phase, and zeroes
Headspace autosampler, sequence editing and GC and/or MS synchronization with Acquility software
Permeation sources for internal mass calibration
Interchangeable ion sources. Learn more about how our API-TOF platform allows easy interchange of ion sources.

Vocus PTR-TOF Publications

2019

Li, H.; et al. Terpenes and their oxidation products in the French Landes forest: insight from Vocus PTR-TOF measurements. Atmospheric Chemistry and Physics, in review 2019. DOI: 10.5194/10.5194/acp-2019-741
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, in review 2019. DOI:10.5194/amt-2018-446

2018

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. DOI:10.5194/amt-12-2403-2019
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 Focus \ DOI: 10.1021/acs.analchem.8b02641

Application Notes

White Papers

Product Information

What is Proton Transfer Reaction Mass Spectrometry (PTR-MS)?

Key Advantages of Proton Transfer Reaction Mass Spectrometry (PTR-MS) · Real-time and simultaneous detection of hundreds of VOCs · Lowest… Read More »

Vocus PTR-TOF Applications

Volatile organic compounds (VOCs) are ubiquitous chemicals that play a significant role in many systems, including health, the environment, food, and industry. Characterization of VOCs can be complicated because they are often trace constituents within complex mixtures. The Vocus PTR-TOF offers unprecedented performances for real-time identification and quantification of VOCs in all fields. The following examples illustrate the instrument’s key advantages. Contact us to discuss other applications or request a demonstration with your samples.

High-Throughput Monitoring of Plant VOCs with an Integrated Vocus PTR-TOF and Autosampler

The interactions of plants with their environment determine their survival in nature and yields in agriculture. Plants can release specific VOCs (volatile organic compounds) to attract beneficial organisms and can detect VOCs as environmental cues. As part of an ongoing research collaboration between the University of Bern Institute of Plant Sciences and TOFWERK, a Vocus PTR-TOF was integrated into a newly developed autosampler. The combination of the fast, ultra-sensitive Vocus PTR-TOF and a novel autosampler, allows quasi-simultaneous, real-time monitoring of over 100 samples with a single mass spectrometer – providing a unique solution for VOC research in plant science and other fields.

Rapid, Sensitive Fentanyl Detection by Thermal Desorption PTR-MS

Widespread opioid abuse causes hundreds of thousands of fatalities worldwide every year. Fentanyl can cause an overdose at concentrations as low as a few to hundreds of ng/ml in the blood. Detection and identification of trace quantities of fentanyl in forensic or biological samples demands very sensitive methods capable of resolving fentanyl within potentially complex backgrounds. This note demonstrates the ability of the TOFWERK Vocus 2R proton transfer reaction time-of-flight mass spectrometer (PTR-TOF) to rapidly identify trace quantities of fentanyl in solution and from the surface of a filter with no sample pre-treatment or separation step.

Profiling Oil and Gas Well Emissions with Mobile PTR-MS

To study the impacts of oil and gas well emissions, researchers from Aerodyne Research deployed a Vocus 2R PTR-TOF to a U.S. production region. In addition to profiling the VOC emissions, these spatially resolved measurements can help identify specific sources of methane, which can be difficult to trace directly because of its higher background levels and large number of sources. Concentrations of the VOCs rapidly decrease as plumes travel from the wells, so accurate mapping of the VOCs requires a detector with ultra-low limits of detection, such as the Vocus PTR-TOF.

Identification of Isobaric VOCs in Coffee Aroma with High Resolution PTR-MS

The breadth of compounds detectable by PTR-MS can hinder analysis of samples containing large numbers of VOCs. If isobars, which have the same nominal mass, are not resolved by the mass analyzer one cannot confidently identify unknown compounds or quantify specific VOCs of interest.

Coffee is known to contain a complex mixture of VOCs that affect flavor, aroma, and color. The head space of coffee was analyzed by direct sampling into the inlet of a VOCUS 2R. The recorded mass spectrum contained thousands of unique peaks, with multiple isobaric peaks resolved at most nominal masses. Comparison of the results to simulations of data measured with reduced resolution demonstrates that confident analysis of complex VOC mixtures demands the high resolving power of the Vocus 2R.

Monitoring Trace VOCs in Human Breath Emissions

Characterization of compounds in human breath emissions can be used for non-invasive diagnosis of diseases, assessment of physiological functions, therapy control, and pharmacokinetic studies. Human breath emissions contains hundreds of VOCs, many at trace concentration levels. Analysis demands ultra-low detection limits, broad dynamic range, and fast time response. In this work, human breath was directly measured throughout the ingestion of a Ricola^TM herb cough drop. The 13 herbs in these cough drops each have their own aroma compounds at concentrations spanning many orders of magnitude. The data capture sub-second changes in VOCs ranging from ppt to ppm concentrations.

Vocus is a Leap Forward in PTR Reaction Cell Design

Traditional PTR reaction cell designs use a stack of metal lenses connected by a series of resistors to produce a linear drift field. The stable, tuneable drift field (E) enables precise control over the distribution of water clusters and the electrostatic reaction time. But, because of scattering and diffusion within the drift tube, many analyte ions are not transmitted out of the drift tube toward the mass analyzer – thereby limiting the achieved sensitivity.

The Vocus reaction cell maintains the operation parameters required for fast, quantitative PTR analysis, with two unique design features that significantly increase sensitivity. By superimposing an oscillating RF field on top of a DC field, analyte ions are focused toward the center axis of the reaction cell and efficiently transmitted into the mass analyzer. The reaction cell is built using a resistive glass tube, rather than the traditional lens stack. This allows the application of the RF focusing field, while producing a more uniform DC field than the traditional lens stack.

Read more about the Vocus reaction cell design and performance in Krechmer, Lopez-Hilfiker, et al, Analytical Chemistry, 2018.