Modifying PTR-MS operating conditions for quantitative headspace analysis of hydro-alcoholic beverages. 1. Variation of the mean collision energy to control ionization processes occurring during PTR-MS analyses of 10-40% (v/v) ethanol-water solutions
2013
Fiches, Guillaume | Deleris, Isabelle | Saint-Eve Delbos, Anne | Pollet, Brigitte | Brunerie, Pascal | Souchon, Isabelle
The analysis of ethanol-containing headspace above alcoholic beverages using proton transfer reaction-mass spectrometry constitute a real analytical challenge because, at standard operating conditions, ethanol reacts with H3O+ reagent ions and leads to their depletion as well as to the formation of several ions from the ethanol. It thus complicates the mass spectrum and has an impact on the stability of ionization conditions. Different methods, mainly based on sample dilution, have been proposed in literature but are not easy to set up. In the present study, we aimed to gain insights into a simpler way to control ionization processes by varying the mean collision energy in the drift tube during the analysis of hydro-alcoholic solutions having an ethanol concentration in the liquid phase ranging between 10% and 40% (v/v). The variation of the E/N ratio enabled the modification of ion kinetic energies and of the density of gas particles in the drift tube. Results showed the abundances of H3O+ reagent ions, (H2O)n H3O+ water clusters and ions issued from ethanol were controlled by varying E/N values from 250 Td to 450 Td, depending on the ethanol content of samples. This study constitutes a first step toward the quantitative analysis of aroma compounds contained in more complex high ethanol-containing beverages. (C) 2013 Elsevier B.V. All rights reserved.
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