Enanthioselectivity of new stationary phase based on ionic liquids with L-aminoacid anions
Abstract
Due to continuous expansion of possibilities of the instrumental analytical methods including gas chromatography (GC), there is a continuous search of new chromatographic materials which extend the possibilities of the method. The same applies to chiral stationary liquid phases (SLP), where the existing range of enantioselective capillary columns is limited. It should be noted that the use of ionic liquids based on chiral anions for capillary gas-liquid chromatography is an original approach is not described in the literature. This also applies to anions based on the amino acids that promising from the point of view of the large variety of available amino acids. In this work the aim of obtaining and studying the selectivity of new chiral phases based on imidazolium ionic liquids (IL) with L-amino acid anions. We study the two ILs: C8MImLeu and C8MImAla with anions on the basis of L-leucine and L-alanine respectively. This ILs were coated to the capillary by a static method followed by enantioselectivity for a number of pairs of enantiomers was measured. Among them: menthol (L, D-isomers), camphor (L,D-isomers) carvone (R,S-isomers), 1,2-Cyclohexyldiamine (RR,SS isomers) α-Methylbenzylamine (R,S-isomers). Measured for them enantioselectivity are in the range of 1.001-1.011. The best enantioselectivity was achieved for the amines (α-Methylbenzylamine, 1,2-Cyclohexyldiamine). Among the ILs the best enantioselectivity showed C8MImAla. Good selectivity and peak parameters for amines may relate to the presence of free amino groups in the structure of the anion. This is perspective for a successful analysis of chiral amino compounds, including amino acids. Thus, first used ILs with chiral anion-based amino acids as material for capillary columns. It is shown that the use of this type of chiral SLP allows one to obtain the coefficients of enantioselectivity the same order as for cyclodextrin based SLP and to achieve good selectivity for amines.
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