Separation of 18α(H)-, 18β(H)-oleanane and lupane by comprehensive two-dimensional gas chromatography

18 alpha(H)-, 18 beta(H)-oleanane and lupane are angiosperm-derived biomarkers that are used as age indicators for the Late Cretaceous onwards when the first proliferation of angiosperms occurred. In addition, the 18 alpha(H)-/18 beta(H)-oleanane ratio is employed as a thermal maturity parameter of crude oil. However, evidence has shown that accurate quantification of these compounds has been impeded by inadequate chromatographic separation by traditional one-dimensional gas chromatography. In this study, we present the separation of 18 alpha(H)-, 18 beta(H)-oleanane and lupane with comprehensive two-dimensional gas chromatography (GC x GC). Furthermore, it was observed that 18 beta(H)-oleanane elutes earlier than 18 alpha(H)-oleanane in second dimension (polarity) which we attribute to steric hindrance effects. Two GC conditions have been developed in order to achieve baseline separation of the triterpenoids of interest in complex mixtures such as sediment extracts and crude oils. (C) 2011 Elsevier B.V. All rights reserved.