Single-walled carbon nanotubes for improved enantioseparations on a chiral ionic liquid stationary phase in GC

Abstract

In order to investigate whether the use of single-walled carbon nanotubes can improve enantioseparations on an ionic liquid stationary phase, a chiral ionic liquid, (R)-N,N,N-trimethyl-2-aminobutanol-bis(trifluoromethanesulfon)imidate, was synthesized. Two capillary columns, one containing the chiral ionic liquid and the other containing the single-walled carbon nanotubes and the chiral ionic liquid, were then prepared for GC. The results of the separations achieved with these columns show that coating the chiral ionic liquid stationary phase onto the capillary column containing single-walled carbon nanotubes improves the enantioselectivety of the chiral ionic liquid. This work indicates that using single-walled carbon nanotubes in this manner enables the application range of such GC chiral separations to be extended.

Application of Carbon Nanotubes in Chiral and Achiral Separations of Pharmaceuticals, Biologics and Chemicals

“…A significant enhancement of the enantioseparation of amlopdipine, propranolol, laudanosine, nefopam, sulconazole and ketoconazole has also been reported by using ionic liquid coating carbon nanotubes with a chiral selector ( Figure 7) [114,115]. Thus, SWCNTs provide a large inner wall for the interaction between the chiral selector and the analytes [37]. This achievement could be extended to more chromatographic columns and for the separation of a wider range of amino acids and chemical analytes in biological and chemical samples.…”

“…Scanning electron microscope images indicated that SWCNTs are attached end to end and produced a network skeletal-like structure [37]. In another experiment, enantioseparation of citalopram has been reported that utilised an ionic liquid coated MWCNTs for buffer modification in CE as compared with the same system without MWCNTs [114].…”

“…A chiral ionic liquid such as (R)-N,N,N-trimethyl-2-aminobutanolbis(trifluoromethanesulfon) imidate has been synthesized [113]. Two columns have been prepared, one containing the chiral ionic liquid only (column A) and the other containing SWCNTs bonded to the chiral ionic liquid (column B) [37]. SWCNTs have been added to a chiral ionic liquid in order to investigate the ability of SWCNTs for the enantioseparation of pharmaceuticals [37].…”

“…The use of nonfunctionalized CNTs for enantioseparations has been reported with nano-HPLC that utilises immobilization or encapsulation on polymer monolithic columns [46]. Functionalized CNTs with chiral selectors have been reported to enhance enantioseparations with HPLC [47], GC [37] and CE [32,48]. The use of unmodified and functionalized CNTs for achiral separations with HPLC [49] and CE [50] have also been reported.…”

Chiral Carbon Nanotubes and Carbon Nanotube Chiral Composites: Preparation and Applications

“…3) was described by Zhao et al, and the separation results showed that the capillary columns coated with the chiral ionic liquid stationary phase containing SWNTs improved the enantioselectivety. 51 A total of 12 racemates including DL-leucine, DL-isoleucine, (AE)-limonene, (AE)-2-phenyl-1-propanol, (AE)-phenylethanol, Fig. 2.…”