Analysis of essential oils and fragrances with a new generation of highly inert gas chromatographic columns coated with ionic liquids

tIn the fields of essential oils and fragrances, samples often consist of mixtures of compounds with similarstructural and physical characteristics (e.g. mono- and sesquiterpenoids), whose correct identificationclosely depends on the synergic combination of chromatographic and mass spectral data. This sam-ple complexity means that new GC stationary phases with different selectivities are continually beinginvestigated. Ionic liquids (ILs) are of great interest as GC stationary phases in this field because of theirselectivity (significantly different than that of currently phases) and their high temperature stability.A first generation of IL GC columns was found to be competitive when applied to these field, interms of selectivity and efficiency, compared to conventional columns (polydimethylsiloxane, (e.g.OV-1), methyl-polysiloxane 5%-phenyl (e.g. SE-52), 7%-cyanopropyl, 7%-phenyl polysiloxane (e.g. OV-1701), and polyethylen glycol (e.g. PEG–20 M). However, these columns showed significant activitytowards polar or active analytes, which primarily affected their quantitative performance. A new gen-eration of highly-inactive columns coated with three of the most widely-used ionic liquid GC stationaryphases has recently been introduced; these phases are SLB-IL60i (1,12-di(tripropylphosphonium) dode-cane bis(trifluoromethylsulfonyl) imide [NTf2], SLB-IL76i (tri-(tripropylphosphonium-hexanamido)-triethylamine [NTf2]), and SLB-IL111i (1,5-di (2,3-dimethyllimidazolium) pentane [NTf2]). This studycarefully tested the new inert IL columns, in view of their routine application in the fragrance and essen-tial oil fields. They were found to have unusually high selectivity, comparable to that of first-generationIL columns, while their inertness and efficiency were competitive with those of currently-used conven-tional columns. The IL column performance of first and second generations was compared, through thequali-quantitative analysis of components in a group of different complexity samples; these includedthe Grob test, a standard mixture of “suspected” skin allergens, and the essential oils of chamomile andsandalwood.