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Liang Zhao - One of the best experts on this subject based on the ideXlab platform.

  • ionic liquid functionalized graphene quantum dot bonded silica as multi mode HPLC Stationary Phase with enhanced selectivity for acid compounds
    New Journal of Chemistry, 2018
    Co-Authors: Yaming Sun, Shuqing Dong, Litao Wang, Jie Gao, Lixiao Chen, Guoying Luo, Liang Zhao
    Abstract:

    Graphene quantum dots (GQDs), which can form hydrophobic, π–π stacking, hydrogen bond and hydrophilic interactions with analytes, are a type of multifunctional separation materials. GQD-based Stationary Phases have great prospects in HPLC. In this study, 1-aminoethyl-3-methylimidazolium bromide ionic liquids (ILs) were chosen as functional molecules to improve the chromatographic performance of GQD-bonded silica Stationary Phase. This new Phase could be applied in multiple separation modes including normal Phase, reverse Phase, ionic exchange and hydrophilic chromatography modes. Anilines, phenols and polycyclic aromatic hydrocarbons were efficiently separated on the IL/GQD/SiO2 column within 10 minutes in the normal Phase and reverse Phase modes. Five inorganic anions were baseline separated in the ionic exchange mode. Hydrophilic compounds including alkaloids, glycosides, amino acids and aromatic acids achieved satisfactory resolutions on this Stationary Phase in the hydrophilic chromatography mode. The separation performance of the IL/GQD/SiO2 column was compared to those of GQD/SiO2 column and IL/SiO2 column; it was found that the IL/GQD/SiO2 column showed better separation performance than the other two columns, which indicated ILs and GQDs had certain synergistic and complementary effects. Introduction of ILs enhanced the separation performance of the GQD-based Phase, especially for acid compounds. By investigating the effects of buffer pH, buffer concentration and water content in the mobile Phase, it was found that the electrostatic adsorption retention mechanism played a major role in the hydrophilic chromatography mode. This Stationary Phase, which allows the selection of appropriate separation modes on the basis of analytes, possesses practical prospects after further improvement.

  • Preparation and Characterization of SiO2/SiO2 Core–Shell Microspheres as RP-HPLC Stationary Phase
    Journal of Inorganic and Organometallic Polymers and Materials, 2011
    Co-Authors: Liu Qin, Wang Litao, Shuqing Dong, Zh.x. Zhang, Liang Zhao
    Abstract:

    Novel SiO2/SiO2 core–shell monodisperse silica spheres for high-performance liquid chromatography packing materials are prepared by the layer-by-layer self-assembly technique. The core–shell silica spheres consist of micrometer-sized porous silica spheres as the core and a thin mesoporous silica shell formed from multilayer nanometer-sized silica particles. In addition, a reversed-Phase packing by bonding octadecyltrichlorosilane on SiO2/SiO2 particles through alkyl-modified method is prepared and characterized. The results show that the carbon content of the new reversed-Phase Stationary Phase increases by approximately 45% compared with the uncoated octadecyl-bonded SiO2 Stationary Phase. Eight kinds of tested aromatic compounds are well-separated on the packing and the peaks are symmetrical, which demonstrates that the packing acts as an excellent reversed-Phase chromatographic Stationary Phase.

  • preparation and characterization of sio2 sio2 core shell microspheres as rp HPLC Stationary Phase
    Journal of Inorganic and Organometallic Polymers and Materials, 2011
    Co-Authors: Qin Liu, Shuqing Dong, Zh.x. Zhang, Litao Wang, Liang Zhao
    Abstract:

    Novel SiO2/SiO2 core–shell monodisperse silica spheres for high-performance liquid chromatography packing materials are prepared by the layer-by-layer self-assembly technique. The core–shell silica spheres consist of micrometer-sized porous silica spheres as the core and a thin mesoporous silica shell formed from multilayer nanometer-sized silica particles. In addition, a reversed-Phase packing by bonding octadecyltrichlorosilane on SiO2/SiO2 particles through alkyl-modified method is prepared and characterized. The results show that the carbon content of the new reversed-Phase Stationary Phase increases by approximately 45% compared with the uncoated octadecyl-bonded SiO2 Stationary Phase. Eight kinds of tested aromatic compounds are well-separated on the packing and the peaks are symmetrical, which demonstrates that the packing acts as an excellent reversed-Phase chromatographic Stationary Phase.

Zhaohui Zhang - One of the best experts on this subject based on the ideXlab platform.

  • preparation of l phenylalanine imprinted polymer based on monodisperse hybrid silica microsphere and its application on chiral separation of phenylalanine racemates as HPLC Stationary Phase
    Separation and Purification Technology, 2012
    Co-Authors: Zhaohui Zhang, Minglei Zhang, Yunan Liu, Xiao Yang, Lijuan Luo, Shouzhuo Yao
    Abstract:

    Abstract In this paper, a l -phenylalanine ( l -Phe) imprinted polymer (MIP) based on monodisperse hybrid silica microspheres (MH-SiO2) with CH CH2 groups was synthesized by surface imprinting technique. The MH-SiO2 was synthesized by a sol–gel process in aqueous media using tetraethylorthosilicate (TEOS) and 3-methylacryloxypropyl trimethoxysilane (MATES) as the precursors. The morphologies of MH-SiO2 and MIP were characterized with scanning electron microscope (SEM) and the imprinted shell thickness on the surface of MH-SiO2 was calculated as 0.5 μm. Compared with the imprinted polymer prepared only by β-cyclodextrin (β-CD) or methacrylic acid (MAA) as functional monomer, the imprinted polymer prepared with both β-CD and MAA as binary functional monomers hold the highest adsorption capacity. Under the optimum chromatographic conditions, a complete baseline separation of phenylalanine racemates was observed only using the column packed with the imprinted polymer prepared with both β-CD and MAA as binary functional monomers. And the separation factor and resolution of the imprinted polymer towards phenylalanine racemates were calculated as 1.41 and 1.46, respectively, which is higher than that of other imprinted polymers.

Shuqing Dong - One of the best experts on this subject based on the ideXlab platform.

  • ionic liquid functionalized graphene quantum dot bonded silica as multi mode HPLC Stationary Phase with enhanced selectivity for acid compounds
    New Journal of Chemistry, 2018
    Co-Authors: Yaming Sun, Shuqing Dong, Litao Wang, Jie Gao, Lixiao Chen, Guoying Luo, Liang Zhao
    Abstract:

    Graphene quantum dots (GQDs), which can form hydrophobic, π–π stacking, hydrogen bond and hydrophilic interactions with analytes, are a type of multifunctional separation materials. GQD-based Stationary Phases have great prospects in HPLC. In this study, 1-aminoethyl-3-methylimidazolium bromide ionic liquids (ILs) were chosen as functional molecules to improve the chromatographic performance of GQD-bonded silica Stationary Phase. This new Phase could be applied in multiple separation modes including normal Phase, reverse Phase, ionic exchange and hydrophilic chromatography modes. Anilines, phenols and polycyclic aromatic hydrocarbons were efficiently separated on the IL/GQD/SiO2 column within 10 minutes in the normal Phase and reverse Phase modes. Five inorganic anions were baseline separated in the ionic exchange mode. Hydrophilic compounds including alkaloids, glycosides, amino acids and aromatic acids achieved satisfactory resolutions on this Stationary Phase in the hydrophilic chromatography mode. The separation performance of the IL/GQD/SiO2 column was compared to those of GQD/SiO2 column and IL/SiO2 column; it was found that the IL/GQD/SiO2 column showed better separation performance than the other two columns, which indicated ILs and GQDs had certain synergistic and complementary effects. Introduction of ILs enhanced the separation performance of the GQD-based Phase, especially for acid compounds. By investigating the effects of buffer pH, buffer concentration and water content in the mobile Phase, it was found that the electrostatic adsorption retention mechanism played a major role in the hydrophilic chromatography mode. This Stationary Phase, which allows the selection of appropriate separation modes on the basis of analytes, possesses practical prospects after further improvement.

  • Preparation and Characterization of SiO2/SiO2 Core–Shell Microspheres as RP-HPLC Stationary Phase
    Journal of Inorganic and Organometallic Polymers and Materials, 2011
    Co-Authors: Liu Qin, Wang Litao, Shuqing Dong, Zh.x. Zhang, Liang Zhao
    Abstract:

    Novel SiO2/SiO2 core–shell monodisperse silica spheres for high-performance liquid chromatography packing materials are prepared by the layer-by-layer self-assembly technique. The core–shell silica spheres consist of micrometer-sized porous silica spheres as the core and a thin mesoporous silica shell formed from multilayer nanometer-sized silica particles. In addition, a reversed-Phase packing by bonding octadecyltrichlorosilane on SiO2/SiO2 particles through alkyl-modified method is prepared and characterized. The results show that the carbon content of the new reversed-Phase Stationary Phase increases by approximately 45% compared with the uncoated octadecyl-bonded SiO2 Stationary Phase. Eight kinds of tested aromatic compounds are well-separated on the packing and the peaks are symmetrical, which demonstrates that the packing acts as an excellent reversed-Phase chromatographic Stationary Phase.

  • preparation and characterization of sio2 sio2 core shell microspheres as rp HPLC Stationary Phase
    Journal of Inorganic and Organometallic Polymers and Materials, 2011
    Co-Authors: Qin Liu, Shuqing Dong, Zh.x. Zhang, Litao Wang, Liang Zhao
    Abstract:

    Novel SiO2/SiO2 core–shell monodisperse silica spheres for high-performance liquid chromatography packing materials are prepared by the layer-by-layer self-assembly technique. The core–shell silica spheres consist of micrometer-sized porous silica spheres as the core and a thin mesoporous silica shell formed from multilayer nanometer-sized silica particles. In addition, a reversed-Phase packing by bonding octadecyltrichlorosilane on SiO2/SiO2 particles through alkyl-modified method is prepared and characterized. The results show that the carbon content of the new reversed-Phase Stationary Phase increases by approximately 45% compared with the uncoated octadecyl-bonded SiO2 Stationary Phase. Eight kinds of tested aromatic compounds are well-separated on the packing and the peaks are symmetrical, which demonstrates that the packing acts as an excellent reversed-Phase chromatographic Stationary Phase.

Shouzhuo Yao - One of the best experts on this subject based on the ideXlab platform.

  • preparation of l phenylalanine imprinted polymer based on monodisperse hybrid silica microsphere and its application on chiral separation of phenylalanine racemates as HPLC Stationary Phase
    Separation and Purification Technology, 2012
    Co-Authors: Zhaohui Zhang, Minglei Zhang, Yunan Liu, Xiao Yang, Lijuan Luo, Shouzhuo Yao
    Abstract:

    Abstract In this paper, a l -phenylalanine ( l -Phe) imprinted polymer (MIP) based on monodisperse hybrid silica microspheres (MH-SiO2) with CH CH2 groups was synthesized by surface imprinting technique. The MH-SiO2 was synthesized by a sol–gel process in aqueous media using tetraethylorthosilicate (TEOS) and 3-methylacryloxypropyl trimethoxysilane (MATES) as the precursors. The morphologies of MH-SiO2 and MIP were characterized with scanning electron microscope (SEM) and the imprinted shell thickness on the surface of MH-SiO2 was calculated as 0.5 μm. Compared with the imprinted polymer prepared only by β-cyclodextrin (β-CD) or methacrylic acid (MAA) as functional monomer, the imprinted polymer prepared with both β-CD and MAA as binary functional monomers hold the highest adsorption capacity. Under the optimum chromatographic conditions, a complete baseline separation of phenylalanine racemates was observed only using the column packed with the imprinted polymer prepared with both β-CD and MAA as binary functional monomers. And the separation factor and resolution of the imprinted polymer towards phenylalanine racemates were calculated as 1.41 and 1.46, respectively, which is higher than that of other imprinted polymers.

Joong Kon Park - One of the best experts on this subject based on the ideXlab platform.

  • Separation of phenylalanine racemates using d-phenylalanine imprinted microbeads as HPLC Stationary Phase
    Separation and Purification Technology, 2008
    Co-Authors: Hamayun Khan, Taous Khan, Joong Kon Park
    Abstract:

    Abstract A successful enantioseparation of d , l -phenylalanine (Phe) was achieved for the first time by using d -Phe imprinted P(MAA-co-EGDMA) microbeads as HPLC Stationary Phase. The d -Phe imprinted microbeads were prepared by a novel modified suspension polymerization method without derivatization of the water-soluble template molecule. This preparation method was employed in order to capture template molecules in organic Phase droplets during polymerization. The prepared d -Phe imprinted P(MAA-co-EGDMA) microbeads were packed into an empty stainless steel column, which was used for the separation of the Phe enantiomers. The selection of a suitable mobile Phase, mobile Phase composition, pH and flow rate were investigated for determining the best resolution of the Phe enantiomers. Baseline separation was achieved using an organic–aqueous buffer (EtOH–acetate buffer) solution as a mobile Phase. Separation factors of more than 2.56, with a resolution of 1.38, were obtained with a mobile Phase containing 9–18% (v/v) EtOH in a 0.030 M acetate buffer solution. d -Phe imprinted microbeads were superior to the majority of the reported molecularly imprinted polymers with respect to chiral separation abilities. The column backpressure was less than 300 psi.