Evaluation of a GC-MS method for the analysis of oregano essential oil composition
2009
Milovanović, I.Lj., Institute for Food Technology, Novi Sad (Serbia) | Mišan, A.Č., Institute for Food Technology, Novi Sad (Serbia) | Sakač, M.B., Institute for Food Technology, Novi Sad (Serbia) | Čabarkapa, I.S., Institute for Food Technology, Novi Sad (Serbia) | Šarić, B.M., Institute for Food Technology, Novi Sad (Serbia) | Matić, J.J., Institute for Food Technology, Novi Sad (Serbia) | Jovanov, P.T., Institute for Food Technology, Novi Sad (Serbia)
The essential oil of oregano (Origanum heracleoticum L.) was analyzed and the presence and relative ratio of 33 compounds was successfully determined using a retention time locked gas chromatographic method. Results show that concentration of the injected essential oil plays a very important role in accurate determination of the compounds. While compounds which comprise a small ratio of the total oil (less than 1%) can only be successfully determined when a relatively high amount of oil is injected, higher concentrations can lead to shift in retention times and less efficient separation of the compounds. Lower essential oil concentrations yield better peak shapes and more efficient separation of components, but trace compounds present in a small amount may not be detected or identified with sufficient certainty in these cases. Identification of essential oil components based solely on their chromatographic data and MS spectra is not reliable method of their determination, since essential oils represent very complex mixtures of sometimes highly similar isomeric compounds with similar mass spectra. Retention time locking, which uses matching of spectral data with the locked retention times in a corresponding compound database can be helpful during such analyses, but there is a need for inclusion of much greater number of compounds in such databases. For this reason, calculation of Kovats indices still represents an important step in identification of similar compounds in highly complex natural products such as essential oils.
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