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PTR-SLIM-TOF: a new dimension of selectivity in real-time

Ion Mobility Spectrometry (IMS) based on Structures for Lossless Ion Manipulations (SLIM) is now complementing Proton-Transfer-Reaction – Mass Spectrometry (PTR-MS). Eliminating the GC compromise: real-time PTR-TOF speed and sensitivity with ultimate IMS selectivity.

The proven power of PTR-TOF technology

Our core PTR-TOF-MS technology is renowned for its incredible speed, enabling the quantification of trace gases in real-time without the need for any sample preparation. Boasting current TOF mass resolutions of up to 25,000 m/Δm and utilizing a wide variety of reagent ions in both positive and negative modes, PTR-TOF inherently delivers exceptional selectivity for a vast array of applications.

Isomer separation in milliseconds

For those highly complex applications that require that final ounce of selectivity – such as the need to separate isomers (molecules with the exact same mass) – we now offer the perfect solution. The new PTR-SLIM-TOF adds an extra data dimension to our high-resolution TOF data: Ion Mobility Spectrometry (IMS).
This innovation brings our technology extremely close to Gas Chromatography (GC-MS), the traditional gold standard for isomer separation. However, our approach retains a decisive, unbeatable advantage: unlike GC, the complete separation and analysis with the PTR-SLIM-TOF still take place in real-time and with zero sample preparation.

Demonstration with real-life data – mass resolution

Fig. 1: High-resolution PTR-SLIM-TOF mass spectrum; even the closest isobars can be separated with about 20,500 m/dm. — Fig. 1: High-resolution PTR-SLIM-TOF mass spectrum; even the closest isobars can be separated with about 20,500 m/Δm.

Cresols (C₇H₈O) and dimethylpyrazines (C₆H₈N₂) play important roles in food, flavor & fragrance analysis. While cresols are known for their smoky, phenolic, and animalic aroma, dimethylpyrazines smell roasted, nutty, and earthy. With a difference in m/z of mere 0.011 only TOF analyzers with paramount mass resolution can separate the two compound classes. Thanks to a mass resolution of >20,000 m/∆m, PTR-SLIM-TOF identifies and independently quantifies cresols and dimethylpyrazines with absolute ease (Fig. 1).

Demonstration with real-life data – IMS resolution

Fig. 2: Only with high-IMS-resolution PTR-SLIM-TOF (FWHM 250 µs) the isobars can be further separated into different isomers and subsequently quantified independently.

Regardless of mass resolution, isomers can never be separated by mass spectrometry alone. Crucially, the two cresol isomers, o-cresol and m-cresol, have a smoky, medicinal, tarry and a smoky, leathery, woody aroma, respectively. Thus, in some fields of application it is necessary to quantify them independently. The same is true for dimethylpyrazines, with 2,3-dimethylpyrazine having a nutty, caramel-like and 2,5-dimethylpyrazine having an earthy, roasted aroma. Particularly in coffee roasting all of these isomers play an important role; therefore, simply separating the isobars might not be sufficient. Further, this demonstration highlights that some cases require high mobility resolution and high mass resolution, as 2,3-dimethylpyrazine and m-cresol both arrive at around 31 ms.

PTR-SLIM-TOF with its extremely high IMS resolution and high mass resolution solves this problem effortlessly. Fig. 2 shows the individual identification of all aforementioned molecules, proving that PTR-SLIM-TOF indeed represents a new dimension of selectivity in real-time.

This product utilizes a sublicense granted by MOBILion Systems to Ionicon for use of the SLIM technology and is protected under their patents.