Published: September 08, 2011 r2011 American Chemical Society 7947 dx.doi.org/10.1021/ac202012u | Anal. Chem. 2011, 83, 7947–7954 ARTICLE pubs.acs.org/ac Evaluation of a Medium-Polarity Ionic Liquid Stationary Phase in the Analysis of Flavor and Fragrance Compounds Carla Ragonese, † Danilo Sciarrone, † Peter Quinto Tranchida, † Paola Dugo, †,‡ Giovanni Dugo, † and Luigi Mondello* ,†,‡ † Dipartimento Farmaco-Chimico, Facolt  a di Farmacia, Universit  a di Messina, Viale Annunziata, 98168ÀMessina, Italy ‡ Universit  a Campus-Biomedico, Via Alvaro del Portillo, 21, 00128 Roma, Italy E ssential oils represent a valuable product widely employed in several fields such as the flavor, fragrance, and food industries. The volatile fraction of essential oils is usually rather complex and can be composed of hundreds of compounds, mainly mono- terpenes, sesquiterpenes, and their oxygenated counterparts, which are separated with great difficulty in a single gas chroma- tography (GC) analysis. It is common to analyze essential oils on both apolar and polar columns for qualitative and quantitative purposes. 1 Nonpolar columns are preferred in the identification of unknown compounds achieved with a mass spectrometer (MS) detector with the support of linear retention index (LRI) data. LRI values, which often present a fluctuating retention behavior on polar columns, are calculated using a reference series of n-alkanes. Polar columns, on the other hand, are often used in order to unravel coelutions that can possibly occur on apolar capillaries. The increasing demands derived from the food and flavor industries for natural and genuine products has increased the requirements of advanced analytical techniques; in this concern, different GC techniques have been exploited for the analysis of essential oils, such as enantio-GC/MS, 2 fast GC methodol- ogies, 3À6 classical multidimensional GC, 7À9 comprehensive 2D GC (GC  GC), 10 and GC-isotope ratio MS; 11 with regards to the liquid chromatography (LC) field, different approaches have been reported such as LCÀMS 12 and comprehensive 2D LC (LC  LC). 13 Although advanced methods can expand the space for separation and/or enhance selectivity, it is also true that many such approaches are often characterized by a high operational complexity, requiring skillful analysts. In almost all separation- science situations, stationary phase selectivity is always a key point in conventional as well as in multidimensional chromatography. Recently, a new class of compounds has received increasing attention for their exploitation as GC stationary phases, namely, room temperature ionic liquids. Room temperature ionic liquids represent a class of organic nonmolecular solvents generally constituted of an organic cation containing N- or P- (i.e., alkyl imidazolium, phosphonium) counterbalanced by an anion of organic or inorganic nature and that are liquid at 20 °C. 14 Ionic liquids have been widely employed in several fields of chemistry. Specific properties such as low volatility, high thermal stability, excellent selectivity toward specific chemical classes, and Received: August 2, 2011 Accepted: September 7, 2011 ABSTRACT: The present research is focused on the evalua- tion, in terms of efficiency and polarity, of a recently introduced gas chromatography (GC) column, coated with a 1,12-di- (tripropylphosphonium) dodecane bis(trifluoromethansulfonyl) amide ionic-liquid stationary phase (SLB-IL59) and its applica- tion to the analysis of a complex essential oil. The ionic liquid column demonstrated very good efficiency, in terms of plate number, and a polarity close to that of the 100% poly- (ethyleneglycol) stationary phase. In this preliminary evalua- tion, the SLB-IL59 30 m column was subjected to bleeding measurements, by means of conventional gas chromatography/ mass spectrometry (GC/MS) and, in addition, of comprehen- sive 2D GC. The SLB-IL59 column (30 m  0.20 μm d f , 0.25 mm i.d.) was then evaluated in the analysis of typical essential oil constituents, in the form of pure standard compounds. Resolution toward several analytes was measured and the results were compared to those obtained with both apolar [silphenylene polymer, equivalent to poly(5% diphenyl/95% dimethylsiloxane)] and medium-polarity [100% poly(ethyleneglycol)] stationary phases, namely, the most common columns employed in the analysis of essential oils; peak symmetry, for different essential oil constituents, was also measured and expressed through tailing factors (at 10% of peak height). The final part of the investigation was devoted to the GC/MS analysis of lemon essential oil, with GC-flame ionization detection (FID) used for quantification. Linear retention indices of all the identified compounds were determined, and the data obtained were compared to those attained on the apolar and “wax” columns. The results obtained in the present investigation reveal the great potential of this novel stationary phase, as a medium-polarity alternative, in the analysis of essential oils.