Headspace Analysis of Volatile Compounds

The headspace analysis by SPME of samples were carried out using a Clarus 500 model Perkin Elmer (Waltham, MA, USA) gas chromatograph coupled with a mass spectrometer and equipped with a FID (flame ionization detector) [19 (link),29 (link)]. The capillary column used for the separation of compounds, was a Varian Factor Four VF-1. The operative chromatographic and spectrometric conditions were as follows: the oven GC temperature program was: isothermal at 60 °C for 5 min, then ramped to 220 °C at a rate of 6 °C min⁻¹, and finally isothermal at 220 °C for 20 min. The carrier gas was He at flow rate of 1.0 mL min−1 in constant mode. The mass spectra were obtained in the electron impact mode (EI), at 70 eV, in scan mode in the range 35–450 m/z. For the identification of compounds, the matching between their mass spectra with those stored in the Nist 02 mass spectra library database, was performed. Further, the linear retention indices (LRIs), were calculated using a series of alkane standards (C₈–C₂₅n-alkanes) and compared with those available in the literature. Relative amounts of compounds, expressed as percentage, were calculated in relation to the total area of the chromatogram by normalizing the peak area without the use of an internal standard and any factor correction. All analyses were carried out in triplicate.