Dicationic ionic liquid stationary phase for GC-MS analysis of volatile compounds in herbal plants

Abstract

The seeming "dual nature" of ionic liquids (ILs) for separating both apolar and polar compounds suggests that ILs may have a great potential for complex samples like essential oils from herbal plants that contain a great variety of compounds. In the present work, a geminal dicationic IL, 1,9-di(3-vinylimidazolium)nonane bis[(trifluoromethyl)sulfonyl]imidate, was investigated for this purpose. To find the best way to achieve satisfactory separations simultaneously for the compounds in essential oils, the dicationic IL was used as the stationary phase for capillary gas chromatography (GC) in two ways, either in its pure state or as a mixed stationary phase with monocationic ILs and a polysiloxane diluent. Interestingly, it was found that the mixed stationary phase exhibited a much better selectivity for polar and nonpolar compounds than either the dicationic IL or the polysiloxane, suggesting that a kind of synergistic effect occurred when these stationary phases were combined in the way described. A comparison with two commercial stationary phases (polar and nonpolar) indicated that this novel mixed stationary phase behaved in a way closer to a polar stationary phase in terms of selectivity and elution order. The present work demonstrates that the mixed stationary phase is efficient and selective and can be an alternative choice for the GC analysis of samples of complex composition.

Capillary column coated with geminal ionic liquids as stationary phases for gas chromatographic separation

“…or organic anions (e.g., NTf2 − , TfO − , etc.). It has been reported that the amount of possible combinations of ionic liquids can be up to 10 18 , because their corresponding cationic/anionic moieties can be easily altered [1].…”

“…Compared with traditional monocationic ionic liquids, geminal ionic liquids exhibited higher thermal stabilities over 350 °C. The operating temperature ranges were also greatly expanded by using geminal ionic liquids as gas chromatographic stationary phases [18]. Moreover, polymerized ionic liquids [19], functionalized ionic liquids [20], and chiral ionic liquids [21] have been exploited in gas chromatography.…”

Separation of Phenol-Containing Pyrolysis Products Using Comprehensive Two-Dimensional Chromatography with Columns Based on Pyridinium Ionic Liquids

“…ILs form a relatively new class of stationary liquid phases that have some advantages, in particular, high thermal stability in comparison with other types of high-polar phases, polarity, and the possibility to control phase selectivity in a wide range [15,16]. Earlier it was shown that the use of columns with ILs provides good separations of various objects: fatty acids, oil products, objects of plant origin, and pesticides [16,17].…”

“…A high contribution of specific interactions is typical of such ILs [16]. Thus, phases with such ILs are highly selective for polar compounds, particularly for phenols [16], which make columns with these phases attractive for separation of objects considered in this work.…”

Ionic liquids in sample preparation

“…Thus, ILs are termed "designable solvents" [8], and various applications have reported for them. In analytical chemistry, ILs were used as stationary phases in gas chromatography [9][10][11], additives for capillary electrophoresis [12][13][14][15], matrices for MALDI [16][17][18], as well as solvents for spectral analysis [19][20][21] and electrochemistry [22]. Several reviews that focus on these topics have been published recently [23][24][25][26][27].…”