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fastGC PTR-TOF – for the best of both worlds

IONICON has developed a fastGC add-on that combines near real-time GC with soft PTR ionization and high resolution TOF.

The new fastGC module adds an optional chemical separation step before the real-time PTR-TOFMS analysis. This combines the complimentary features of gas chromatography with real-time trace gas analysis offering intriguing new possibilities. Developed as an add-on for IONICONs PTR-TOF instruments, the fastGC comprises a short, commercial GC column with an innovative heating concept for ultra-fast heating and cooling rates.

It seems that Innsbruck has always been a hotspot for novel developments in trace gas analysis. Erika Cremer, a lecturer at the University of Innsbruck, and her co-worker Fritz Prior have built the first gas chromatograph in the 1940s. Although their academic paper had not been published for the next 30 years, since the printing press being destroyed in an air strike, Gas Chromatography coupled to Mass Spectrometry (GC-MS), has become the key technology for analysis of trace gas concentrations.

In the mid 1990’s another novel technology for real-time trace gas analysis has been implemented at the institute of Ion-physics at the University of Innsbruck. Proton transfer reaction mass spectrometry (PTR-MS) is a chemical ionization method that allows to monitor and quantify trace gas levels in real-time. This compelling new technology was commercialized by our company and has experienced a rapid propagation since.  We consider ourselves the world-leader in developing, manufacturing and marketing PTR technology, constantly thriving for better performance and new innovation. “A key advantage of PTR-MS is to see trace concentrations in real-time. Compared to the discrete sample analysis in GC-MS, this is like the step from classical photography to a movie.”, says Dr. Alfons Jordan, one of the inventors of the PTR-MS and a founder of IONICON.

This speed in analysis of PTR-MS has been further boosted a few years ago with the introduction of time-of-flight based systems. These IONICON PTR-TOF systems analyse the full spectrum in a split second with a high mass resolution that allows separating and identify isobaric compounds (compounds with the same nominal mass, but different chemical composition). Nevertheless, the separation of isomeric compounds (compounds with the same chemical composition) has remained an advantage of GC-MS. Although this is possible in PTR-MS by selecting different pre-cursor ions (SRI), the resulting spectra can easily become too complex for rich samples.

To address this issue, we have developed a so-called fastGC. This add-on provides a chemical pre-separation step for PTR-TOF systems. A typical GC spectrum takes about 30 minutes, while in PTR-TOF a full spectrum can be acquired every 100 ms – 18,000 times faster.

product_fastGC_xylene-separationThe fastGC system is designed to provide fast spectral runs. Achieving a comparably small chemical separation is sufficient, since it is complemented by the PTR-TOFs high mass resolving power. The figure shows m/z 107.086 in a fastGC PTR-TOF measurement. On this m/z we typically observe protonated Xylene (C8H10.H+). The fastGC is able to separate the two isomers p- and o-Xylene, that were in the sample in equal concentrations.

product_fastGC_setupThe IONICON fastGC add-on, contains a short commercial GC column. To provide fast spectral runs the column utilizes a novel heating concept in which the column is directly, resistively heated. This minimal thermal mass allows for fast heating and, more importantly, also for fast cooling rates of 30°C/s (that is 1800 °C/min). These are impressive specifications for any fastGC system and suggest that it could also be interesting apart from its combination with PTR-TOF. The temperature is precisely controlled and custom temperature ramps can easily be programmed. With the appropriate ramp-setting spectral runs within less than 1 minute can be realized. This brings gas chromatographic separation much closer towards real-time analysis. The fastGC add-on is integrated with the PTR-TOF and the normal sample gas inlet is utilized. This allows researchers to perform real-time measurements and add fastGC runs at time points of interest for enhanced separation and identification.

An additional advantage is the separation of compounds present in high concentrations. If one compound exceeded the upper limit of detection of ~10 ppm in a PTR-TOF, a dilution of the sample was recommended. Such is the case for the high ethanol concentrations in the head-space of alcoholic beverages. A recent publication used an early prototype of IONICON’s fastGC system to analyse wine samples. Romano and his co-workers could demonstrate several advantages of fastGC-PTR-TOF [2]. While the ethanol is separated and does no longer impair the analysis, several isomeric compounds could be resolved, which can be used for an enhanced separation of different wine samples.

More information:

[1] fastGC Product Homepage

[2] Andrea Romano et al., Wine analysis by FastGC proton-transfer reaction-time-of-flight-mass spectrometry, (2014) International Journal of Mass Spectrometry,369, p. 81–86

[3] Poster (2014) PTR-TOFMS: Latest improvements in selectivity and sensitivity

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