Unambiguous identification of volatile organic compounds by proton-transfer reaction mass spectrometry coupled with GC/MS.
Interest in on-line measurements of volatile organic compounds (VOCs) is increasing, as sensitive, compact, and affordable direct inlet mass spectrometers are becoming available. Proton-transfer reaction mass spectrometry (PTR-MS) distinguishes itself by its high sensitivity (low ppt range), high time resolution (200 ms), little ionization-induced fragmentation, and ionization efficiency independent of the compound to be analyzed. Yet, PTR-MS has a shortcoming. It is a one-dimensional technique that characterizes compounds only via their mass, which is not sufficient for positive identification. Here, we introduce a technical and analytical extension of PTR-MS, which removes this shortcoming, while preserving its salient and unique features. Combining separation of VOCs by gas chromatography (GC) with simultaneous and parallel detection of the GC effluent by PTR-MS and electron impact MS, an unambiguous interpretation of complex PTR-MS spectra becomes feasible. This novel development is discussed on the basis of characteristic performance parameters, such as resolution, linear range, and detection limit. The recently developed drift tube with a reduced reaction volume is crucial to exploit the full potential of the setup. We illustrate the performance of the novel setup by analyzing a complex food system.
Nestlé Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland.
Christian
C
Lindinger
Philippe
P
Pollien
Santo
S
Ali
Chahan
C
Yeretzian
Imre
I
Blank
Tilmann
T
Märk
D003069:Coffee / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D009930:Organic Chemicals / Q000032:analysis*; D014835:Volatilization
D003069:Coffee; D009930:Organic Chemicals