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Comprehensive two-dimensional gas chromatography/mass spectrometric analysis of pepper volatiles

Authors

  • Z. L. Cardeal,

    Corresponding author
    1. Chemistry Department, ICEx, Federal University of Minas Gerais, Avenida Antonio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil
    • Chemistry Department, ICEx, Federal University of Minas Gerais, Avenida Antonio Carlos 6627, 31270-901 Belo Horizonte, MG, Brazil.
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  • M. D. R. Gomes da Silva,

    1. REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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  • P. J. Marriott

    Corresponding author
    1. Australian Centre for Research on Separation Science, RMIT University, Department of Applied Sciences, GPO Box 2476V Melbourne 3001, Australia
    • Australian Centre for Research on Separation Science, RMIT University, Department of Applied Sciences, GPO Box 2476V Melbourne 3001, Australia.
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Abstract

The headspace compositions of 13 pepper and peppercorn samples of different species, colloquially also referred to as pepper, were analyzed, and more than 300 compounds were tentatively characterized by means of comprehensive two-dimensional gas chromatography in tandem with flame ionization detection, quadrupole mass spectrometric detection and time-of-flight mass spectrometric detection (GC × GC-FID, GC × GC/qMS and GC × GC/TOFMS, respectively). The analysis of volatile organic compounds (VOCs) was performed after solid-phase microextraction (SPME) using a 75-µm PDMS/DVB fibre. Fingerprint comparison between the three techniques permitted peaks to be assigned in the GC × GC-FID experiment based on the analogous MS analysis, taking into account retention shifts arising from method variations.

When using GC × GC/TOFMS, about five times more peaks were identified than in GC × GC/qMS. Retention indices for all peaks were calculated in the bi-dimensional column set comprising of a 5% phenyl polysilphenylene-siloxane primary column and a polyethylene glycol second column. The spectra obtained by both mass detection techniques (qMS and TOFMS) give very similar results when spectral library searching was performed. The majority of the identified compounds eluted as pure components as a result of high-resolution GC × GC separations, which significantly reduces co-elution, and therefore increases the likelihood that pure spectra can be obtained. The differences between TOFMS and qMS (in fast scanning mode) spectra were generally small. Whilst spectral quality and relative ion ratios across a narrow peak (e.g. wb ∼ 100–150 ms) do vary more for the fast peaks obtained in GC × GC/qMS operation, than with TOFMS, in general adequate spectral matching with the library can be achieved. Copyright © 2006 John Wiley & Sons, Ltd.

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