Jun-Hui Zhang

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.

Chiral 3D Open‐Framework Material Ni(D‐cam)(H2O)2 Used as GC Stationary Phase

Metal-organic frameworks (MOFs) have been explored for analytical applications because of their outstanding properties such as high surface areas, flexibility and specific structure features, especially for chromatography application in recent years. In this work, a chiral MOF Ni(D-cam)(H2O)2 with unusual integration of molecular chirality, absolute helicity, and 3-D intrinsic chiral net was chosen as stationary phase to prepare Ni(D-cam)(H2O)2-coated open tubular columns for high-resolution gas chromatographic (GC) separation. Two fused-silica open tubular columns with different inner diameters and lengths, including column A (30 m × 250 µm i.d.) and column B (2 m × 75 µm i.d.), were prepared via a dynamic coating method. The chromatographic properties of the two columns were investigated using n-dodecane as the analyte at 120 °C. The number of theoretical plates (plates/m) of the two metal-organic framework (MOF) columns was 1300 and 2750, respectively. The racemates, isomer and linear alkanes mixture were used as analytes for evaluating the separation properties of Ni(D-cam)(H2O)2-coated open tubular columns. The results showed that the columns offered good separations of isomer and linear alkanes mixture, especially racemates.

A chiral porous organic cage for molecular recognition using gas chromatography

Molecular organic cages as shape-persistent organic molecules with permanent and accessible cavities have attracted a lot of interest because of their importance as host-guest systems. Herein, we report a chiral porous organic cage (POC) CC9 diluted with a polysiloxane OV-1701 to fabricate a CC9-coated capillary column, which was used for the high-resolution gas chromatographic separation of organic compounds, including positional isomers and racemates. On the CC9-coated capillary column, a large number of racemic compounds such as chiral alcohols, esters, ethers and epoxides can be resolved without derivatization. By comparing the chiral recognition ability of the CC9-coated column with the commercially available β-DEX 120 column and the POC CC3-R coated column recently reported by our group, the CC9-coated column offered good resolution during the separation of some racemates, that were not separated using the β-DEX 120 column or POC CC3-R coated column. Therefore, the CC9-coated column can be complementary to the β-DEX 120 column and CC3-R coated column. The results indicated that the CC9-coated column exhibited great potential for application in the separation of positional isomers and enantiomers with great selectivity, high resolution and good reproducibility.

Highly selective separation of enantiomers using a chiral porous organic cage

Porous solids composed of shape-persistent organic cage molecules have attracted considerable attention due to their important applications such as molecular separation, heterogeneous catalysis, and gas storage. In this study, an imine-linked porous organic cage (POC) CC10 diluted with a polysiloxane OV-1701 was explored as a novel stationary phase for high-resolution gas chromatography (GC). A wide variety of enantiomers belonging to different classes of organic compounds have been resolved on the coated capillary column, including chiral alcohols, esters, ketones, ethers, halohydrocarbons, epoxides, and organic acids. The fabricated column complements to commercial β-DEX 120 column and our recently reported CC3-R column for separating enantiomers, which indicates that the excellent chiral recognition ability of CC10 is not only interesting academically, but also has potential for practical application. In addition, CC10 also exhibits good selectivity for the separation of n-alkanes, n-alcohols, Grob mixture, and positional isomers. This work also indicates that this type of chiral POCs will become a new class of chiral selector in the near future.

A 3D Homochiral MOF [Cd2(d-cam)3]•2Hdma•4dma for HPLC Chromatographic Enantioseparation

Up to now, some chiral metal-organic frameworks (MOFs) have been reported for enantioseparation in liquid chromatography. Here we report a homochiral MOF, [Cd2(d-cam)3]·2Hdma·4dma, used as a new chiral stationary phase for high-performance liquid chromatographic enantioseparation. Nine racemates of alcohol, naphthol, ketone, and base compounds were used as analytes for evaluating the separation properties of the chiral MOF packed column. Moreover, some effects such as mobile phase composition, column temperature, and analytes mass for separations on this chiral column also were investigated. The relative standard deviations for the resolution values of run-to-run and column-to-column were less than 2.1% and 3.2%, respectively. The experimental results indicate that the homochiral MOF offered good recognition ability, which promotes the application of chiral MOFs use as stationary phase for enantioseparation.

A novel inorganic mesoporous material with a nematic structure derived from nanocrystalline cellulose as the stationary phase for high-performance liquid chromatography

Chiral nematic mesoporous silica (CNMS) is a novel inorganic mesoporous material that has properties of both mesoporous and liquid crystal materials. In this work, we report CNMS as a stationary phase for high-performance liquid chromatographic (HPLC) separation of positional isomers. High-resolution separation of aminophenol, dihydroxybenzene, nitroaniline, nitrophenol, chloroaniline, bromoaniline, iodoaniline, dinitrobenzene, nitrochlorobenzene and nitrobromobenzene isomers on CNMS columns was performed. Slurry-packed CNMS columns had better selectivity than commercial β-cyclodextrin HPLC columns for separating these positional isomers. The effects of mobile phase composition, injected analyte mass and column temperature on separation were investigated. The relative standard deviations for five replicate separations of positional isomers were 0.10–0.43% for the retention time and 0.5–3.9% for the peak area. Therefore, CNMS columns are promising for separating positional isomers based on their good reproducibility, high resolution and excellent selectivity. In addition, the column also exhibits recognition ability toward racemates.

A highly ordered chiral inorganic mesoporous material used as stationary phase for high-resolution gas chromatographic separations

A highly ordered chiral mesoporous silica-coated capillary column has been used for high-resolution gas chromatographic separations. The column has excellent selectivity, not only for the separation of isomers, polycyclic aromatic hydrocarbons, linear alkanes, long chain alkanes, Grobs test mixture and aromatic hydrocarbons, but also for the resolution of different classes of chiral compounds. Additionally, the column exhibits high column efficiency, excellent temperature resistance, and analysis times are short. This is the first report of a highly ordered chiral inorganic mesoporous silica used in separation science.