Improved mass accuracy in PTR-TOF-MS: Another step towards better compound identification in PTR-MS

Proton transfer reaction mass spectrometry (PTR-MS) provides on-line monitoring of volatile organic compounds (VOCs) with a low detection threshold and a fast response time. Commercially available set-ups are usually based on quadrupole analysers that, due to the unit mass resolution, do not provide useful analytical information besides the nominal mass of the ions detected. Recently new instruments based on time-of-flight (PTR-TOF-MS) analysers have been proposed and commercialized. They provide higher mass resolution and thus improve the analytical information contained in the spectra. Mass accuracy, however, is an issue that has not been considered in great detail in the published papers on PTR-TOF-MS so far. We show here that the mass accuracy obtained by a commercial apparatus can be improved by proper data analysis. In particular, internal calibration based on an improved algorithm allows for a mass accuracy that suffices for elemental determination in the most common situations. Achieving good mass accuracy is a fundamental step for further exploiting the analytical potential of PTR-MS. (C) 2009 Elsevier B.V. All rights reserved.