Enhanced collection of essential oil components by using a multidimensional GC-prep system

The request for terpene compounds has greatly increased in the last decades due to their capability to enhance/provide pleasant flavour and fragrance. Furthermore, the continuous efforts to found new flavours and fragrances necessitate an effective collection system to provide this compounds from natural sources. GC coupled to preparative system has proven to be a valid tool for collection of volatile and semi-volatile compounds but often this procedure is time-consuming, difficult to optimize and frequently characterized by low recovery values requiring a high number of collections. Furthermore, in some case it is very difficult to collect pure compounds, due to the partial or total coelutions, by using low-efficiency wide-bore or packed GC columns. To overcome these problems an MDGC system has been coupled to a preparative system (Figure 1) with the purpose of increasing the amount of volatile compounds that can be collected in each single GC run due to their higher sample capacity. The wide-bore columns in both chromatographic dimensions allowed the possibility to inject high sample amounts of neat essential oil, maintaining an acceptable efficiency level. Even if in some case the sample amount overloaded the primary apolar column, compromising the separation of the target compound, the heart-cut of this fraction on the second dimension polar column allowed the purification of the compound before the collection (Figure 2). This option has proven to be very useful, reducing the relative time and cost. The method has been validated in terms of recovery collection for different amounts of volatile compounds.