title: Towards gas chromatography-mass spectrometry coupling protocols for both identifying and quantification essential oils of Thymus capitatus Hoff et Link.
abstract: Essential oil of Thymus capitatus Hoff et Link is analysed by using four techniques: GC/pyrolyse/MS, GC/FID, electronic impact GC/MS (quadripole), and GC/MS (ion trap). Both major and trace components are analysed. The GC/pyrolyse/MS coupling provides reference to the exact mass compositions without any need of the previously purified references, neither for major or trace components. The comparison between this reference analysis and GC/FID shows that the FID response coefficients may vary by a mean 7% from one component to another. As it was expected, quadripole or ion trap response coefficients vary to a much greater extent (a mean 25%), although the two MS techniques response coefficients are first order consistent. We conclude that GC/MS coupling could be used not only as it is usual for reliable identifications, but also for a complete quantitative routine analysis of essential oils. Expected precision could be very similar to GC/FID precision provided correcting species by species the MS analysis by a mean value of the response coefficient measured for the MS 70 eV electronic impact ionisation technologies. The GC/pyrolyse/MS coupling is proposed as a relevant tool for analysing reference samples containing trace natural species that could not be purified.
authors.affiliation: Unité de Recherche Physico-Chimique Moléculaire--IPEST-BP51, La Marsa 2070, Tunisia. lassaad.hedhili@issatgb.rnu.tn
authors.forename: Lassaad
authors.initials: L
authors.lastname: Hedhili
authors.forename: Mehrez
authors.initials: M
authors.lastname: Romdhane
authors.forename: Henri
authors.initials: H
authors.lastname: Planche
authors.forename: Manef
authors.initials: M
authors.lastname: Abderrabba
mesh_terms: D002138:Calibration; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D009822:Oils, Volatile / Q000032:analysis*; D015203:Reproducibility of Results; D046930:Thymus Plant / Q000737:chemistry*
chemical_list: D009822:Oils, Volatile