Automated on‐line HPLC‐HRGC with gradient elution and multiple GC transfer applied to the characterization of citrus essential oils

Abstract

AbstractCitrus essential oil analysis is characterized by the complexity of the separation of all the components which may belong to different classes of compounds and be present in a wide range of concentrations.Capillary GC is the best technique for characterizing the volatile fraction of citrus essential oil. In many cases, however, this technique does not achieve complete separation of all the components.A combination of LC and HRGC in off‐line methods is necessary to achieve complete resolution of the minor components present in the oil and in general to facilitate the identification of the components belonging to different classes. Very recently we have demonstrated the possibility of using on‐line HPLC‐HRGC coupling for fractionation and identification of alcohols in lemon oils.In the present work, a fully automatic HPLC‐HRGC instrument was used for the pre‐separation of the essential oils into the various classes of compounds, using gradient elution and multiple fraction transfer into the capillary column.This method allowed a pre‐separation of the components into four major classes of compounds: hydrocarbons, aldehydes, esters, and alcohols before their transfer into the GC. A good correlation with the existing off‐line methods was found.The ability of the Instrument to perform, In a fully automatic way, HPLC pre‐separation with gradient elution and GC transfer of more than one fraction from a single HPLC injection, was found to be very useful for routine characterization of various essential oils.