Li-Ming Yuan

Chiral metal-organic frameworks for high-resolution gas chromatographic separations.

Chiral metal-organic framework coated open tubular columns are used in the high-resolution gas chromatographic separation of chiral compounds. The columns have excellent selectivity and also possess good recognition ability toward a wide range of organic compounds such as alkanes, alcohols, and isomers.

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

AbstractIn 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. FigureChromatograms of (±)-phenylethanol racemates on a chiral ionic liquid column (a) and a column containing SWNTs and the chiral ionic liquid (b)

(R)‐N,N,N‐Trimethyl‐2‐Aminobutanol‐Bis(Trifluoromethane‐Sulfon)Imidate Chiral Ionic Liquid Used as Chiral Selector in HPCE, HPLC, and CGC

Abstract In this work, the (R)‐N,N,N‐trimethyl‐2‐aminobutanol‐bis(trifluoromethanesulfon)imidate chiral ionic liquid was first used in chromatography and exhibited a excellent chiral recognition ability in high performance capillary electrophoresis (HPCE), high performance liquid chromatography (HPLC), and capillary gas chromatography (CGC), which also showed for the first time that chrial ionic liquid was an effective chiral selector in HPCE and HPLC. The compounds that have been separated using this chiral ionic liquid at least included alcohol, amine, acid, and amino acid, et al. enantiomers. As the chiral ionic liquid can be easily synthesized from relatively inexpensive materials, it should have a great potentiality for chiral separation in chromatographic science.

Homochiral Porous Organic Cage with High Selectivity for the Separation of Racemates in Gas Chromatography

Porous organic molecular cages as a new type of porous materials have attracted a tremendous attention for their potential applications in recent years. Here we report the use of a homochiral porous organic cage (POC) (CC3-R) diluted with a polysiloxane (OV-1701) as a stationary phase for high-resolution gas chromatography (GC) with excellent enantioselectivity. A large number of optical isomers have been resolved without derivatization, including chiral alcohols, diols, amines, alcohol amines, esters, ketones, ethers, halohydrocarbons, organic acids, amino acid methyl esters, and sulfoxides. Compared with commercial β-DEX 120 and Chirasil-L-Val columns, the CC3-R coated capillary column offered more preeminent enantioselectivity. In addition, CC3-R also exhibits good selectivity for the separation of isomers, linear alkanes, alcohols, and aromatic hydrocarbons. The excellent resolution ability, repeatability, and thermal stability make CC3-R a promising candidate as a novel stationary phase for GC. The study described herein first proves useful commercially. This work also indicates that porous organic molecular materials will become more attractive in separation science.

Enantioselective chromatographic resolution using a homochiral metal–organic framework in HPLC

A homochiral MOF was used as a new chiral stationary phase and had an excellent recognition ability for various racemates in HPLC. The results indicated that the optical selectivity of the natural chiral MOF column is practical in HPLC, which promotes the application of chiral MOFs for enantioseparation.

Novel inorganic mesoporous material with chiral nematic structure derived from nanocrystalline cellulose for high-resolution gas chromatographic separations.

Chiral nematic mesoporous silica (CNMS) has attracted widespread attention due to some unique features, such as its nematic structure, chirality, large pore size, high temperature resistance, low cost, and ease of preparation. We first reported the use of CNMS as a stationary phase for capillary gas chromatography (GC). The CNMS-coated capillary column not only gives good selectivity for the separation of linear alkanes, aromatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and isomers but also offers excellent enantioselectivity for chiral compounds. Compared with enantioseparations on commercial β-DEX 120 and Chirasil-l-Val columns, a CNMS-coated capillary column offers excellent enantioselectivity, chiral recognition complementarity, and the separation of analytes within short elution times. It can also be potentially applied in high-temperature GC at more than 350 °C. This work indicates that CNMS could soon become very attractive for separations.

Porous Chiral Metal-Organic Framework InH(D-C10H14O4)2 with Anionic-Type Diamond Network for High-Resolution Gas Chromatographic Enantioseparations

Metal-organic frameworks have large surface area, highly ordered pore structure and good chemical stability. In this study, a porous chiral metal-organic framework InH(D-C10H14O4)2(D-C10H14O4 = D-(+)-camphoric acid) with a left-handed helical channel assembled from D-(+)-camphoric acid was used as chiral stationary phase in GC. InH(D-C10H14O4)2-coated open tubular columns with different inner diameters or lengths were prepared by a dynamic coating method for high-resolution GC separation of various types of organic compounds, including racemates, isomers, alkanes, alcohols, and Grobs test mixture. Their column efficiency, polarity, and selectivity were studied. The experimental results show that the stationary phase has excellent selectivity and also possesses good recognition ability toward these organic compounds, especially for chiral compounds.

Experimental comparison of chiral metal-organic framework used as stationary phase in chromatography

Chiral metal-organic frameworks (MOFs) are a new class of multifunctional material, which possess diverse structures and unusual properties such as high surface area, uniform and permanent cavities, as well as good chemical and thermal stability. Their chiral functionality makes them attractive as novel enantioselective adsorbents and stationary phases in separation science. In this paper, the experimental comparison of a chiral MOF [In₃O(obb)₃(HCO₂)(H₂O)] solvent used as a stationary phase was investigated in gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The potential relationship between the structure and components of chiral MOFs with their chiral recognition ability and selectivity are presented.

Recent progress of chiral stationary phases for separation of enantiomers in gas chromatography.

Chromatography techniques based on chiral stationary phases are widely used for the separation of enantiomers. In particular, gas chromatography has developed rapidly in recent years due to its merits such as fast analysis speed, lower consumption of stationary phases and analytes, higher column efficiency, making it a better choice for chiral separation in diverse industries. This article summarizes recent progress of novel chiral stationary phases based on cyclofructan derivatives and chiral porous materials including chiral metal-organic frameworks, chiral porous organic frameworks, chiral inorganic mesoporous materials, and chiral porous organic cages in gas chromatography, covering original research papers published since 2010. The chiral recognition properties and mechanisms of separation toward enantiomers are also introduced.

Capillary electrochromatographic fast enantioseparation based on a chiral metal–organic framework

Metal–organic frameworks (MOFs) have received great attention because of their unusual properties and fascinating structures in separation sciences. However, to the best of our knowledge, there has been no attempt to utilize chiral MOFs as stationary phases in packed‐CEC. Here, a chiral MOF [In3O(obb)3(HCO2)(H2O)]·solvent (4,4′‐oxybisbenzoic acid) was explored as the chiral stationary phase in packed‐CEC for separation of chiral compounds and isomers. The fabricated [In3O(obb)3(HCO2)(H2O)]·solvent packed capillary columns gave fast enantioseparation of (±)‐hydrobenzoin, (±)‐1‐phenyl‐1,2‐ethanediol, and clenbuterol within 3 min in CEC. Besides, the baseline separations of nitrophenol isomers within 6 min were also achieved. The RSDs for the retention time of run‐to‐run, day‐to‐day, and column‐to‐column reproducibility were 1.51–3.63, 1.83–3.98, and 3.42–5.66%, respectively. These results demonstrate that chiral MOFs are promising for enantioseparation in CEC.