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Benefits of Proton Transfer Reaction - Mass Spectrometry

PTR-MS (Proton Transfer Reaction – Mass Spectrometry) is the benchmark method for simultaneous real-time monitoring of volatile (organic) compounds (VOCs) without sample preparation in very low concentrations.
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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, 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,
  • and no sample preparation is necessary.

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

IONICON combines the unique PTR ionization with state-of-the-art Mass Spectrometry (MS): Take advantage of the IONICON-built modular and flexible ioniTOF Time-of-Flight (TOF) MS platform which we use for our renowned PTR-TOFMS product portfolio.

IONICON PTR-MS has become the benchmark method for simultaneous real-time monitoring of VOCs in ambient air with wide range of applications. Over 600 leading scientists, institutions and multinational corporations are among our customers. For more details, watch our webinar "A short introduction to PTR-MS".

Already convinced? Then go and a look at our PTR-MS product portfolio or continue reading below to learn more about the "gold standard" in real-time organic trace analysis!

What are the benefits of PTR-MS?

Originally developed by scientists at the Institut für Ionenphysik at the University of Innsbruck, Austria, PTR-MS has been commercialized by IONICON Analytik since 1998. We develop and manufacture ultra-sensitive real-time trace gas analyzers based on PTR-MS and other ionization technologies. In over 25 years more than 600 PTR-MS instruments were sold to our customers.

Online quantification without calibration
PTR-MS is based on chemical ionization mass-spectrometry with many advantages over conventional CIMS, providing absolute quantitative analysis in real-time. The generation of the precursor reagent ions and the chemical ionization of the VOCs are individually controlled and spatially separated processes. This leads to constant and well defined conditions in the drift tube (unlike IMS, APCI-MS and similar technologies) making the determination of absolute concentrations possible without the continuous use of gas standards.

Market-leading low online detection limit
H3O+ ions do not react with any of the major components present in clean air due to their low proton affinity. Unlike other technologies (e.g. SIFT-MS or IMR-MS) PTR-MS does not dilute low concentrated samples by a carrier gas and does not lose precursor ions on their way through a mass filter between the ion source and the drift tube. This makes PTR-MS very sensitive to trace gases in the sample air. Very high intensities of precursor ions and thus real sub pptv-range detection limits for our PTR-TOF instruments, are the resulting benefits.

Soft and efficient chemical ionization - fully controlled ion chemistry
Proton transfer from H3O+ is a soft, low energetic ionization method with suppressed fragmentation of substances as compared to e.g. electron impact ionization often used in GC-MS instruments, thus minimizing complex mass spectra and improving the identification capability. However, another benefit of PTR-MS is that the energy level (E/N) in the PTR drift tube where the actual ionization takes place, can even be adjusted by the user. This allows to precisely control and adapt the ion chemistry to the application. Learn more on an IONICON-grade PTR-MS and its ion chemistry quality.

Selective Reagent Ionization - Mass Spectrometry (SRI-MS)
By using not only H3O+ but also NO+, O2+ and NH4+ or Kr+ and Xe+, as an optional reagent ion configuration, separation of isomeric compounds in real-time is now possible. Additionally, nearly all substances that could not be ionized with H3O+ due to their low proton affinity are detectable.
Note: Because of a highly sophisticated ion source design (hollow cathode discharge) we do not need a signal-diminishing mass filter to select these precursor ions, thus we can achieve outstanding sensitivity also for SRI-MS.

No sample preparation
A major advantage of PTR-MS is that the samples do not need to be prepared before the measurement (e.g. pre-concentration or chemical separation procedures), thus whole-air samples can be introduced directly into the drift tube allowing for dynamic headspace sampling or VOC flux measurements. We also offer multiplexing and autosampling solutions.

The real-time advantage
PTR-MS is an "online" mass spectrometric technology providing real-time data due to its very fast response time of less than 100ms, allowing e.g. for BVOC flux measurements. Averaging over minutes and long sampling intervals as in the case of less sensitive or "offline" technologies are not necessary with an IONICON PTR-TOF. This is also an asset for our fast and automated industrial process monitoring solutions.

Advanced time-of-flight MS technology
Time-of-flight based trace gas analyzers as compared to mass filter (quadrupole) based technologies (e.g. SIFT-MS or IMR-MS) have many advantages, such as:
- better separation and identification capabilities due to higher mass resolution and
- the acquisition of the entire mass range in a fraction of a second (quadrupoles require the same time for only one single mass to be analyzed) which increases speed and sensitivity dramatically, especially for complex mixtures. Benefit from the modular and flexible ioniTOF-MS plaform for your PTR-TOF instrument.

Robust and easy to use
No gas supply is necessary to operate an IONICON PTR-MS (i.e. for H3O+ and NO+ reagent ions). Our instruments are light-weight and space-saving which clearly puts PTR-MS ahead of competing technologies. IONICON PTR-MS systems are often used for field campaigns or variable location measurements and can be operated in nearly every environment. Remote connection, operation and support capabilities are fully implemented e.g. via the free "Teamviewer" application. Little maintenance and small operating costs complete the whole package.

You're not yet convinced? Click here for some testimonials and references of our customers or let us do a free showcase for you!

Are you looking for scientific background information? Click here or download the IONICON technologies overview!

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