A novel method for terpene pattern determination of essential oils by selectivity tuning in GC

Summary Selectivity tuning is used in a system of series-coupled GC-columns of different polarity in order to improve the analysis of complex samples of essential oils. It is shown that selectivity tuning by changing the flow-rates in the single columns can be used for improving both the resolution and the reliability of identification. Furthermore, by combining this method with column switching techniques (multidimensional GC) a reduction of sample complexity could be reached. Isothermal retention indices of 35 terpenoid compounds were ascertained using a non-polar and a polar capillary column serving as the input-values of a computer program which enables the prediction of system retention times at any adjusted flow-rate. Therefore, promising chromatographic conditions for the separation of interesting compounds could be selected without great experimental effort and some of these compounds could be identified with a high degree of reliability.