Employing a hyphenated analytical technique, gas chromatography-matrix isolation-Fourier transform-infrared spectrometry-flame ionization detection (GC-MI-FT-IR-FID), the chemical characteristics of a series of natural product essential oils are presented. The technique allows for the separation (GC), isolation (MI), identification (IR), and quantitation (FID) of the components of the essential oils. The oils examined in this study are derived from conventional processes such as steam distillation as well as from supercritical fluid extraction processes. Definitive structure determinations are possible at quantities of material less than 10 ng for compounds differing only in isomer conformations (cis versus trans). This manuscript represents the first report of the successful application of this approach to the analysis of essential oil type mixtures.