Select-eV enables the energy of ionising electrons in GCMS to be changed by allowing the production of reference-quality electron ionisation mass spectra with conventional full-fragmentation patterns, and repeatable ‘soft-ionisation’ spectra exhibiting reduced fragmentation and an enhanced molecular ion.
Previous attempts to develop soft electron ionisation have been compromised by a dramatic drop in sensitivity. Other approaches to soft ionisation have also been limited by the inconvenience of reagent gases or source exchange. Select-eV overcomes all these problems by maintaining or enhancing sensitivity, without the need to reconfigure the system or add reagents, the desired ionisation energy is simply selected as part of the method setup in the controlling software. Energies can be varied anywhere from standard 70 eV down to 10 eV. The molecular ion is enhanced at lower energies but a degree of structurally significant fragmentation is also maintained. This makes Select-eV perfect for any GC–MS analyst needing further confirmation of compound identity, or wanting to distinguish between compounds with spectra that are very similar at 70 eV.
Nick Bukowski, Mass Spectrometry Business Unit Manager at Markes, stated “Lowering the energy of electron ionisation usually causes a dramatic drop in sensitivity, but Select-eV overcomes this problem. In fact, the signal-to-noise ratios of many compounds are increased at lower energies. This is a crucial advantage of Select-eV for trace analysis and for challenging samples such as the complex mixtures of hydrocarbons routinely investigated in the petrochemical industry.”
Select-eV is available with the BenchTOF range of time-of-flight mass spectrometers from Markes International and will be launched at the HTC-13 conference in Bruges, Belgium, from January 28. The company will also be presenting their world-leading range of innovative thermal desorption technology for automated extraction/concentration of trace organics in air and materials.

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