Frequently Asked Questions

What does the abbreviation "PTR-MS" stand for?

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.

How does PTR-MS ionize the substances?

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+.

How is mass separation of the ions done?

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.

What are the advantages of PTR-MS compared to conventional mass spectrometry?

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…

What are the advantages of PTR-MS compared to SIFT-MS?

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.

What are the advantages of PTR-MS compared to gas chromatography?

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...

What are the advantages of PTR-MS compared to SIFT-MS?

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.

How does PTR-MS compare to SIFT-MS, APCI, MS-e-noses, other CIMS and related direct injection mass spectrometry methods?

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.

Other manufacturer's systems are sometimes also called "PTR-MS", what's the difference to a real IONICON PTR-MS?

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.