Optimization of comprehensive two-dimensional gas-chromatography (GC×GC) mass spectrometry for the determination of essential oils.

Comprehensive two-dimensional gas-chromatography (GC×GC) is a great tool to explore complex essential oils. In this work the different terpene composition of the aroma fraction of rosemary and oregano were studied. The present investigation is based on the optimization of the comprehensive two-dimensional gas-chromatographic method through the use of experimental designs and Multisimplex, and studying the modulation period, discharge-time and first and second column flows. Making use of a non-polar column (HP-5) in the first dimension and an intermediate one (DB-17) in the second dimension, we concluded that 1.42s, 0.12s, 1.23 mL/min and 17.55 mL/min were our optimum values, respectively. The use of a highly polar phase in the second dimension did not make any significant improvement. Finally, aroma quantification of the studied plants was performed by means of the optimum method achieved and functional groups "bands" were studied. The essential oil concentration ranges obtained were, 0.04-6.6 μg/g for rosemary extracts and 0.04-0.5 μg/g for oregano extracts.