Gas chromatography combined with mass spectrometry, flame ionization detection and elemental analyzer/isotope ratio mass spectrometry for characterizing and detecting the authenticity of commercial essential oils of Rosa damascena Mill.

RATIONALE The essential oil of Rosa damascena Mill. is known for its fine perfumery application, use in cosmetic preparations and for several pharmacological activities. Due to its high value, it can be easily adulterated with flavors or cheaper oils. This study is aimed at a detailed phytochemical characterization of commercial samples of R. damascena essential oil and at their authenticity assessment. METHODS Nineteen commercial samples of R. damascena essential oil of different geographic origin and an additional authentic one, directly extracted by hydro-distillation from fresh flowers, were considered. GC-MS and GC-FID techniques were applied for the phytochemical analysis of the samples. EA-IRMS (Elemental Analysis–Isotope Ratio Mass Spectrometry) and GC/C(Combustion)-IRMS were used to determine the delta-13C composition of bulk samples and of some specific components. RESULTS Citronellol (28.7-55.3%), geraniol (13.5-27.3%) and nonadecane (2.6-18.9%) were the main constituents of Bulgarian and Turkish essential oils, while those from Iran were characterized by a high level of aliphatic hydrocarbons (nonadecane: 3.7-23.2%). The delta-13C values of bulk samples were between –28.1 and –26.9‰, typical for C3 plants. The delta-13C values of specific components were in the usual range for natural aromatic substances from C3 plants, except for geranyl acetate, which displayed higher values (up to –18‰). These unusual delta-13C values were justified by the addition of a natural cheaper oil from a C4 plant (Cymbopogon martinii, palmarosa), which was found to occur in most of the essential oils. CONCLUSION GC/C-IRMS, in combination with GC-MS and GC-FID, can be considered as an effective and reliable tool for the authenticity control of R. damascena essential oil.