Retention divergence of terpenes with porous graphitized carbon and C18 stationary phases

The significant divergence between the retention of 16 terpene standards on porous graphitized carbon (PGC) and C-18 packing materials are illustrated. The PGC surface is shown to provide a selectivity toward shape, polarity, and structure that is not afforded by the C-18 surface. This observation is illustrated by plots of the retention factors similar to those typically used to represent 2D-HPLC separations. A geometric approach to factor analysis was used to measure the separation divergence together with the selectivity and the product selectivity factors of closely related species. When a methanol mobile phase was used with the PGC surface, a large fraction of the separation space could be utilized. That is further reflected by a spreading angle of 80.3 degrees. The PGC material was also successful at resolving structural isomers where the C-18 phase was not. It was also found that the choice of the mobile phase is important when using this material. A much larger degree of space utilization was seen with methanol than with acetonitrile that displayed a spreading angle of only 40.8 degrees. (c) 2012 Elsevier B.V. All rights reserved.