The World's Leading PTR-MS Trace Analyzers Company

Frequently Asked Questions

We collect your questions related to the our technologies, products and our company. Here we answer them for you. If you cannot find what you are looking for please contact us!

PTR-MS technology

PTR-MS is the abbreviation for Proton Transfer Reaction - Mass Spectrometry, allowing for real-time measurement of volatile organic compounds (VOCs) at even very low concentrations. Originally developed by scientists at the Institut für Ionenphysik at the University of Innsbruck, Austria and the founders of our company, this technology has been commercialized by IONICON Analytik.

In a drift tube protonated water (H3O+) interacts with molecules that possess a higher proton affinity than water. This means that one proton switches from H3O+ to the molecule (M) and therefore produces MH+.

Customers may choose between a quadrupole mass filter in PTR-QMS series and a time-of-flight mass analyzer in PTR-TOFMS series systems. Compare advantages of quadrupole and time of flight here. Time of flight mass spectrometers due to their high mass resolving power can separate between isobars, hence allow for identification of compounds which have the same nominal mass. The Selective Reagent Ionization - Mass Spectrometry (SRI-MS) technology allows for identification of even some isomers. With the  fastGC add-on IONICON instruments now have GC capabilities - chemical separation in combination with real-time measurements. Unique to PTR-MS - and a major advantage over e.g. SIFT-MS - is the capability to change the energy levels in the drift tube, which suppresses or increases fragmentation. Distinct fragmentation patters that are observed by varying this energy levels (E/N) foster the identification capabilities of IONICON PTR-MS further. This method is used in our air monitoring solutions.

PTR is a soft chemical ionization process, which means that in contrast to electron impact or charge transfer ionization the fragmentation rates can be kept very low. Therefore, absolute concentrations can be derived immediately. In addition, common compounds of ambient air do not get ionized, which makes mass spectra easily interpretable and accounts for very low online detection limits in the pptv-range. Learn more...

Unlike SIFT-MS, PTR-MS does not dilute low concentrated samples by any carrier gas and lose precursor ions to the mass filter between the source and the drift tube, hence PTR-MS is much more sensitive, has a lower detection limit and does not need any gas supply (proton transfer from H3O+ ions). Our instruments are light-weight (i.e. the portable PTR-QMS 300 weights only 70 Kg) and space-saving which clearly puts us ahead of technologies like SIFT-MS. Moreover, only PTR-MS is available in a range of time-of-flight (TOF) based PTR-TOF instruments which has a lot of advantages. Last but not least, unlike with SIFT-MS, energy levels (E/N) in the drift tube can be varied in PTR-MS, catering to better identification capabilities. PTR-MS and SIFT share a common history. Learn more about the evolution from SIFT to PTR-TOF which resulted in ultimate performance and technological perfection.

With PTR-MS, substances do not need any pretreatment and can be measured online, in real-time over a range of six orders of magnitude down to a minimum concentration of less than 1 pptv (depending on the model). Even relatively fast GC-MS systems work with much longer time spans and are therefore considered as an "offline" method.  Learn more...

Unlike SIFT-MS, PTR-MS does not dilute low concentrated samples by any carrier gas and lose precursor ions to the mass filter between the source and the drift tube, hence PTR-MS is much more sensitive, has a lower detection limit and does not need any gas supply (proton transfer from H3O+ ions). Our instruments are light-weight (i.e. the portable PTR-QMS 300 weights only 70 Kg) and space-saving which clearly puts us ahead of technologies like SIFT-MS. Moreover, only PTR-MS is available in a range of time-of-flight (TOF) based PTR-TOF instruments which has a lot of advantages. Last but not least, unlike with SIFT-MS, energy levels (E/N) in the drift tube can be varied in PTR-MS, catering to better identification capabilities. PTR-MS and SIFT share a common history. Learn more about the evolution from SIFT to PTR-TOF which resulted in ultimate performance and technological perfection.

PTR-MS is generally much more sensitive than SIFT-MS (according to the authors around two orders of magnitude). The “downside” of PTR-MS, providing only one type of precursor ions (H3O+, the most important type though) has been overcome by a technology we call Selective Reagent Ionization - Mass Spectrometry (SRI-MS), where H3O+, NO+ and O2+ can be produced in the IONICON ion source with even higher yields than SIFT-MS. Also the possibility to use several energy levels (E/N) in the drift tube is not possible with SIFT-MS, but this feature enhances the unique substance identification capabilities of PTR-MS significantly. Compared to APCI, a widely used technology, PTR-MS allows for more accurate quantification due to a controlled and very efficient ionization, offering higher sensitivity. Compared to many other CIMS, IONICON PTR-MS has a well controlled and straightforward ionization process which results in 4 important ion-chemistry qualities only available from IONICON. Moreover, the new EVR PTR-MS technology offers the fastest response time in the CIMS market. PTR-MS is extremely versatile, used in various applications and is commercially available as IONICON’s product portfolio: ultra-sensitive quadrupole or high-resolution time-of-flight based systems.

Learn more...

PTR-MS has been invented by the founders of our company and now more than 20 years later, is more popular than ever before. Sometimes other instrument manufacturers call their system "PTR-MS" or "H3O+ CIMS" etc. if they use proton transfer by H3O+ as their primary ionization technique. But there's much more to an IONICON PTR-MS. A real PTR-MS is characterized by 4 important ion-chemistry quality dimensions which enable quantitative real-time results and are only available from IONICON. Learn more about the essentials of an IONICON-grade PTR-MS.

PTR-MS instruments

When you decide for a PTR-MS you will not only receive the instrument, but an ample package including a computer, comprehensive software package, detailed documentation, all needed cables and lines, toolkit and much more, so that you can start your work immediately. Moreover one of our or our partner's specialists will visit you for installation & on-site training.

As long as the instrument is turned off, it is highly portable and can be moved via mounted wheels or handrails (depending on the model). During operation, shocks should be avoided to prevent the turbo pumps from getting damaged. However, with special shock absorbing housings it is possible to use our PTR-MS devices in airplanes and other vehicles. Learn more about in-the-field environmental research. Our engineers can work out a solution for you!

We deliver our instruments fully equipped with a 1.2m inlet hose consisting of an internal inert PEEK capillary, heating (up to 180°C) and thermal insulation. The flow is adjustable between 50 and up to 1000 sccm via a digital mass flow controller. Customized inlet solutions (e.g. second inlet line, different lengths or heating capacities, multiplexing systems)  are available too.

Yes! Several turbo molecular pumps and membrane pumps (oil-free) are part of the system and controlled by the internal electronics. Compared to other analytical instruments, the noise level is very low. No external pumping station is necessary.

The only consumable besides electric power is distilled water. An internal water reservoir has to be refilled approximately every 3-6 months. No carrier gases or other expensive consumables are needed. If you are using Selective Reagent Ionization - Mass Spectrometry (SRI) O2 and filtered air or NO need to be supplied for precursor ion generation. SRI+ users need Kr or Xe for reagent ion creation.

Sure! Just contact us and our experts will be happy to suggest solutions so that your solution fits your needs in every way. We have experience in designing special products tailored to your needs. Learn more...

Yes! Each of our instruments has ample interfaces (please check the specifications of the instrument you are interested in). Additionally we offer interface adapters - the IONICON I/O box - with many analog in-/outputs as well as digital in-/outputs. The quantity of interfaces is scalable. Please contact us for more information.

Yes! Our PTR-MS instruments are completely computer controlled and connected via Ethernet. Just connect the system to the internet and you can remote control it from everywhere you like. For support purposes our staff uses and recommends Teamviewer as remote access tool, helps you tune and troubleshoot if needed. This process allows for hassle free and convenient remote customer support, while you can focus on the real important task: your experiment.

Although operating a PTR-MS instrument is very simple and intuitive, we offer an installation & training package, where one of our experts will give you a training session upon delivery of the system directly at your site.
Additionally we cordially invite you to our biennial "hands-on PTR-MS" training course in the framework of the international PTR-MS conference. Individual training sessions are available on demand.

Detectable substances

IONICON uses a soft ionization method based on proton transfer from H3O+ ions to all compounds with a higher proton affinity than water. Common constituents of air such as N2, O2, Ar, CO2 etc. have lower proton affinities than H2O and do therefore not interfere with the measurement. This is one of the main reasons for our market-leading low online detection limit for trace compounds in the range of a few pptv.

Most of the common VOCs have higher proton affinities than H2O and thus can be monitored and quantified down to single-digit pptv-levels and even sub-pptv.

With our latest development that offers the possibility to switch between multiple reagent ions, we are now able to significantly extend the number of compounds that can be analyzed with our instruments.

Please check the Proton Affinity (PA) of your desired molecule (e.g. in databases like the NIST chemistry webbook or ask our experts). If it is higher than the PA of water (165.2 kcal/mol) it is detectable. Learn more...

Yes! We are happy to invite you to our company site to give you the opportunity to test the PTR-MS technology directly with the substances you bring along. We call this: YOUR showcase. Together with our experts you can discover our products and make valuable experiments tailored to your application. We also offer analytical services, from single tests to whole studies. Just contact us and let us know how we can help.

Yes! Just connect an appropriate line to the exhaust outlet of the instrument. The instrument's vacuum system may be contaminated though and special caution is necessary when services or maintenance shall be carried out. Please contact our experts if you have more questions or would like us help you with service and maintenance.

Every substance, no matter if solid or liquid, has a certain vapor pressure depending on its temperature. Therefore the substance is always also present in its gaseous form and can be measured as long as the concentration is above the detection limit. Our Liquid Calibration Unit (LCU) can also be used as a precise evaporation tool that allows you to create a vapor of certain liquids that you are interested in.

Yes! The new CHemical Analysis of aeRosol ON-line (CHARON) particle inlet coupled to IONICON PTR-TOFMS instruments quantitatively detects organic sub-µm particulate matter as well as particulate ammonium and nitrate at single digit ng/m³ mass concentration levels in real-time. Therefore, we offer monitoring of almost the full range of atmospheric organic carbon with one single instrument, from gas-phase volatile and intermediate volatile organics (VOC and IVOC) to particle-phase intermediate, semi and low volatile organic compounds (IVOC, SVOC and LVOC, respectively).

 Isobars, having the same nominal mass, but different sum formula: These compounds can be distinguished with one of our PTR-TOFMS series instruments, if the mass resolution is sufficient for the mass difference between the isobars.

- One substance fragments into another substance of interest, or two different substances braking up into the same fragment. As an example, if you have a linear chain of a hydrocarbon, e.g. Octane C8H18 and Nonane C9H20 they are only detectable with O2+. Due to the fact that ionization with O2+ is not as soft as ionization with H3O+ there will be more fragmentation. This may lead to both substances fragmenting into smaller hydrocarbon chains (C2Hx, C3Hx, C4Hx,...) which makes it very difficult to distinguish between these compounds. This could be also a problem for e.g. Tetrachloroethane C2Cl4H2 and Methylenechloride, which could both easily fragment into CHCl2.

- Different isomers (same sum formula) in a sample (e.g. 1-propanol and 2-propanol): they will be summed up on the same nominal mass, the detection limit and the calculated concentration is an aggregate of both substances. Recent IONICON developments allow to use a fastGC add-on with a PTR-MS which enables chemical separation. Ask us for more information.

- Compounds having the same sum formula, but a different structure: e.g. 2-Heptenal and Cycloheptanone (C7H12O) where the 2-Heptenal is an aldehyde and Cycloheptanone is a ketone. These two substances can be distinguished using NO+ because aldehydes and ketones undergo different reactions with NO+. Therefore the substances are detected on different masses.

- We can stimulate or suppress fragmentation by increasing or decreasing the energy in our PTR drift tube (E/N). This is a unique feature to PTR-MS and allows to separate several substances based on their ion branching ratios, i.e. the different patterns of fragmentation in relation to the E/N, which often are not alike. We make use of this method in our Automated Measurement and Evaluation (AME) air monitoring software.

Selective Reagent Ionization - Mass Spectrometry (SRI-MS)

H3O+ is ideal for many applications as our customers have proven for more than a decade. In some cases however it can be useful to use more than one reagent ion in your PTR-MS. By using SRI isomeric VOC compounds can be separated and instantaneously quantified (the differentiation of isobaric compounds is already possible by using IONICON PTR-TOFMS series). NO+ is like H3O+ a soft ionizer, ionization occurs mainly through charge transfer, whereas O2+ is found to be a less soft chemical ionization agent and can be used where proton transfer from H3O+ does not work. Kr+ has an ionization energy of 14.0 eV which is well above all reagent ions utilized in PTR-MS instruments so far and allows for nearly all substances to be detectable. Learn more on SRI-MS.

Once your instrument is SRI enabled, there is no hardware change required for switching between the SRI ionization modes. Some system parameters have to be changed. This is done via software and a cylinder of O2 and a charcoal filter for NO have to be attached to the instrument. Signals of the desired precursor ions are visible immediately and after approximately 10 seconds, measurements can start. After 30 seconds the signal should be stable. The ion switching is possible without adding a mass filter which would reduce the instrument sensitivity significantly (e.g. at SIFT-MS instruments).

Yes. The software offers you the possibility to program sequences where the instrument is switching between different settings. The ionization mode can be changed automatically too.

Usually the flow into the ion source is between 5 and 10 sccm. This is equivalent to a consumption of gas (at atmospheric pressure) of around 0,3 to 0,6 liters per hour.

Performing a measurement

No! The sample or air can be analyzed directly without the need of any pretreatment which is a major advantage compared to "offline" methods like GC-MS.

The fastest possible response time is < 100ms. Results are provided in real-time. The temporal resolution is enough for flux measurements and unlike in quadrupole-based instruments (e.g. SIFT-MS or IMR-MS) the whole mass spectrum is analyzed at the same time in our PTR-TOF systems. There is no waiting for a quadrupole to select one substance's mass after the other.

Depending on the model, the lowest measurable concentration is below 1 pptv (we have proven ppqv-range detection limits). Have a look at our product range and our dedicated PTR-TOFMS performance data page.

The detection range is linear from 10ppmv (or for higher-sensitive PTR-TOF systems: approximately a factor 10 lower) down to the detection threshold, which is five to six orders of magnitude depending on the model. Compare our products here. If your sample has VOCs in higher concentration than upper linearity-range limit we can propose special dilutions systems, allowing to accurately quantify even higher concentrations. Have a look at our customization page.

No! High humidity or even changes in the humidity during a measurement do not cause a problem for PTR-MS. There is a very small minority of substances where actual detection limit we can reach is depending on humidity. Please have a look at the next FAQ for more details.

Yes! Formaldehyde has only a slightly higher proton affinity than water (hydronium ions are used to perform the proton transfer) and therefore back reactions are possible with water. This results in a somewhat higher limit of detection for formaldehyde and a minority of substances which are in the same proton affinity range than water. The reactions in this case are humidity depending.
There is another concern with regards to Formaldehyde: the mass filters (quadrupoles) in the two systems PTR-QMS 300 and High Sensitivity PTR-QMS 500 have an influence to the detection limit of Formaldehyde. Formaldehyde has a molecular mass of 31 amu (protonated). Therefore it can happen that O2 (which is always present in our spectra because of the PTR-technology) gives a small background on mass 31 depending on the performance of the quadrupole. For the PTR-QMS 300 instrument this fact leads to a detection limit for formaldehyde of better than 10 ppbv depending on the instrument settings.
The High Sensitivity PTR-QMS 500 instrument has a much better performing quadrupole for separating different masses hence detection limits for formaldehyde lower than 0,5 ppbv are possible. In general we recommend time of flight based instruments with high mass resolution for such applications.

No! PTR-MS uses ambient air as a buffer gas when operating with H3O+ ions. This means that when using PTR-MS, unlike in e.g. SIFT-MS instruments, your sample won't be diluted with a carrier gas which is one of the reasons for our market-leading limit of detection.

Yes! You can monitor concentrations online and in real-time. There is a continuous flow of sampled air through the PTR-MS system that is analyzed immediately and time of flight based instruments (e.g. PTR-TOF series) analyze the whole mass range at the same time. Thus all substances a PTR-MS can detect, are recorded continuously and in parallel, not sequentially which is the case in quadrupole based analyzers (e.g. SIFT-MS or IMR-MS). 

Our instruments are calibrated carefully prior to delivery and do not need to be frequently recalibrated. For highly accurate results calibrations with gas standards are recommended from time to time. IONICON offers a range of sophisticated trace calibration systems, based on gas or liquid standards and zero air. Learn more on our LCU calibration devices.

If the instrument is not in use it can be set to "stand-by" or "idle" mode for timescales of up to several weeks. In this mode the instrument is ready to start measurements within seconds. If the instrument was switched off for a longer period or the vacuum system has been ventilated, the system has to be pumped until an appropriate vacuum level is reached.

No! Measurements can be done continuously one after another.

No! Measurements (including e.g. switching of external valves) can be done fully automated. Various safety mechanisms take care that sensitive parts are shut down automatically. Remote control tools are available.

Depending on the user's preference, the PTR-MS software displays and saves values as raw data (counts per second or Ampere) and in absolute concentrations (ppbv or µg/kg).

In operation, the PTR-MS only consumes electric power (max. 650-1.500W; depending on the model) and very small amounts of distilled water (approx. 2-4 liters a year), so the operating costs are outstandingly low. For the use of other precursor ions, reagent gases have to be supplied in small quantities.


Yes! There is an ample software package included, ranging from the operating system of the enclosed laptop or built-in industrial PC to the mass analyzer software. In addition we enclose our PTR-MS software package that was programmed by our in-house software department. Depending on the instrument type you buy from us, you'll typically get the PTR-MS suite including operating software but also the PTR-MS Viewer tool allowing to perform post processing operations of PTR-TOFMS and PTR-QMS data.

Yes! External devices (e.g. electronic valves, flow controllers etc.) can be controlled via the PTR-MS software. This allows e.g. automated switching between different samples during a long-term measurement. The PTR-MS software is undergoing continuous improvements and there other external devices such a certain multiplexing valves that can also be controlled with our software. Please ask if you have special requirements.


Our customers are active in a lot of different fields of research: Atmospheric chemistry, in environmental research and trace gas analysis (e.g. emissions in urban and remote areas, indoor spaces, vehicles), food and flavor science (e.g. analysis of coffee, olive oil, butter, cheese, wine, herbal extracts and aromas). We also develop industrial VOC monitoring solutions (e.g. in semiconductor industry, waste incineration plant, chemical factories and production sites). Read more about some typical PTR-MS applications.

The IONICON blog frequently features stories about special applications.


No! PTR-MS instruments have exceptionally long maintenance intervals in the range of up to six months.

Yes! We offer maintenance contracts for our systems that cover the regular service work. We can propose very flexible service offers that are adapted to your budget. Our specialists do the maintenance work quickly and efficiently, ensuring that your system is configured and operated in optimal conditions. Please contact us if you want to know more about it.

For us, customer care is not only words, it's a relationship that we take serious. Fast and competent answers to urgent questions via email or telephone, for ordering spare parts, software updates, suggestions how to solve complex problems, etc. go without saying. We undertake regular customer and user surveys to evaluate the quality of our service and we receive top marks throughout. If you have questions about an IONICON system or need help, please contact us.


We would be happy to welcome you at our company site. Just contact us. Here you can also find your way to our location. 

Yes! Bring your samples along with you or let us demonstrate our instruments to you in a real lab application situation. See what you can get here! Just write us an email or call us.

You can find an up-to-date list of distribution partners on our website. If we are not locally represented in your country we sell and support our products directly from our company site in Austria. Learn more...

IONICON participates in exhibitions and conferences frequently. Please check our events schedule for up-to-date information about upcoming exhibitions and conferences. We would be happy to meet you there.

We're glad you are here! Have a look at our current vacancies and if you don't find what you are looking for, don't hesitate and just submit an initiative application where you tell us about your talents and what you would like to accomplish at IONICON. Quite a few of our team came aboard that way.