Potential of the reversed-inject differential flow modulator for comprehensive two-dimensional gas chromatography in the quantitative profiling and fingerprinting of essential oils of different complexity

• Beneficial effects of reverse inject differential flow-modulation GC × 2GC–FID/MS.
• Higher efficiency of band re-injection with improved 2D peak-widths and symmetry.
• Better handling of the overloading phenomenon without loss of peak-capacity.
• Highly reliable quantitative profiling of medium complexity essential oils.
• Informative fingerprinting of highly complex essential oils (vetiver).

In this study, the first capillary flow technology reverse-inject differential flow modulator was implemented with different column configurations (lengths, diameters and stationary phase coupling) and detector combinations (mass spectrometry – MS and flame ionization detection – FID) to evaluate its potential in the quantitative profiling and fingerprinting of medium-to-highly complex essential oils. In particular, a parallel dual-secondary column dual-detection configuration that has shown to improve the information potential also with thermally modulated GC × GC platforms (MS identification reliability and accurate FID quantitation), was tested. Several system performance parameters (separation measure SGC×GC, modulation ratio MR, separation space used and peak symmetry) were evaluated by analyzing a mixture of volatiles of interest in the flavor and fragrance field. The systems demonstrating the best chromatographic performance were selected for quantitative profiling of lavender and mint essential oils and fingerprinting of vetiver essential oil. Experimental results demonstrate that careful tuning of column dimensions and system configurations yields improved: (a) selectivity; (b) operable carrier gas linear velocities at close-to-optimal values; (c) 2D separation power by extending the modulation period and (d) handling of overloaded peaks without dramatic losses in resolution and quantitative accuracy.