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Chinese Journal of Chromatography
2020, Vol. 38, No. 4
Online: 08 April 2020

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Volume 38, Number 4 Content 2020, 38 (4):  0-0.  Abstract ( 18 )   PDF (6172KB) ( 20 )

Mini-reviews

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Advances in polymer-based dendrimer-grafted chromatographic separation materials ZHI Mingyu, HE Yi, GUO Dandan, ZHU Yan 2020, 38 (4):  366-371.  DOI: 10.3724/SP.J.1123.2019.07022 Abstract ( 91 )   HTML ( 7 )   PDF (1480KB) ( 107 )   With the continuous developments in stationary phase preparation technology and materials science, numerous modification methods and new materials have been employed for the functional modification of the polymer stationary phases in solid-phase extraction, high performance liquid chromatography and ion chromatography. In particular, because of their unique structure and properties, poly(amidoamine) (PAMAM) dendrimers play an important role in improving the structure and performance of chromatographic separation materials. In this paper, the application of PAMAM to the modification of polymer-based chromatographic separation materials is reviewed, and further developments are prospected.

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Research progress on core-shell silica stationary phases for high performance liquid chromatography XIA Hongjun, LIU Jiawei, BAI Quan 2020, 38 (4):  372-382.  DOI: 10.3724/SP.J.1123.2019.08014 Abstract ( 150 )   HTML ( 13 )   PDF (1948KB) ( 113 )   Fast and efficient separation by using high performance liquid chromatography (HPLC) is challenging for a wide range of samples. In recent years, core-shell silica microspheres have been widely investigated and used for highly efficient and fast separation under reasonably low pressure for small solutes, biopolymers, and complex samples. In this paper, the mechanism for fast separation and preparation methods of core-shell silica microspheres are introduced, along with their application for HPLC-based separation of small molecules, peptides, and biological macromolecules in HPLC. The developing trends of using core-shell microspheres in HPLC are also presented.

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Research progress in hydrothermal carbon materials for separation and analysis ZHAO Xingyun, ZHANG Hongyan, NIU Huan, WU Ren’an 2020, 38 (4):  383-391.  DOI: 10.3724/SP.J.1123.2019.08026 Abstract ( 106 )   HTML ( 3 )   PDF (2683KB) ( 55 )   Hydrothermal carbon materials are new functional materials prepared by the hydrothermal reaction of sugars or carbonaceous organic compounds. They have many advantages such as abundant resources of raw materials, environmental-friendliness, hydrophilicity, and easy of modify and so on. These carbon materials have been widely used as catalyst carriers, energy electrode materials, environmental adsorbents, etc. Among these, the application of hydrothermal carbon materials as absorbents reveals their ability to show strong interactions with specific molecules. In recent years, the application of these materials has been gradually extended to the field of chromatography, as stationary phases for solid-phase separation as well as for the enrichment of complex biological samples. In this paper, the recent applications of hydrothermal carbon materials for the analysis of ionic compounds, polar compounds, phosphorylated peptides, and glycopeptides are presented. Finally, the future scope of these materials in separation and enrichment is also discussed.

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Application of calixarene stationary phases to liquid chromatography ZHANG Guangrui, ZHANG Wenfen, GUO Yun, ZHANG Suning, ZHANG Shusheng 2020, 38 (4):  392-398.  DOI: 10.3724/SP.J.1123.2019.08027 Abstract ( 125 )   HTML ( 7 )   PDF (977KB) ( 54 )   Calixarenes are cyclic oligomers composed of phenol units linked by methylene bridges. Because of their unique host-guest recognition ability, calixarenes are considered to be the main representatives of the third generation of supramolecular chemistry after crown ethers and cyclodextrins. Calixarenes are widely used in ion channel as well as in organic catalytic reactions, transmembrane transport, purification, and chromatographic separation. A variety of versatile calixarene derivatives with different recognition ability and special selectivity were prepared by modifying different types of compounds due to calixarenes are easy to derivatize. These derivatives were successfully applied to different chromatographic modes to achieve the separation and analysis of complex samples. This review summarizes the recent advances in stationary phases based on calixarenes and their derivatives for liquid chromatography The prospects of calixarenes in chromatographic separation science are also presented.

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Preparation and characterization of open tubular ion chromatographic columns HUANG Weixiong 2020, 38 (4):  399-408.  DOI: 10.3724/SP.J.1123.2019.08020 Abstract ( 111 )   HTML ( 4 )   PDF (2428KB) ( 51 )   In recent years, significant progress has been made in the area of open tubular ion chromatography (OTIC). In particular, gradient OTIC has been realized through the development of hydroxide eluent-compatible OTIC columns. This review covers the preparation and characterization of different OTIC columns, ranging from the historic silica-based columns to the newly emerging polymer-based open tubular (OT) columns. The preparation of various OTIC stationary phases, from grafted to latex agglomerated and monolayer to multilayer phases, has been briefly introduced. The characterization of electrostatic latex agglomerated OTIC columns has been extensively discussed, e. g. fluorescent ion displacement chromatography, frontal displacement chromatography, and frontal reaction chromatography have been used to measure the capacities of OT columns, and the results are compared with the theoretical calculation values. The variable αiex, defined as the number of ion-exchange equivalents per unit surface area, is used as an indicator of the capacity of OT columns, to enable a straightforward comparison between OT columns having different inner diameters (i.d.). The newly introduced column capacity parameter, γiex, defined as the stationary phase capacity per unit liquid volume present, is used to investigate the relationship between packed and OT columns when using the same stationary phase. Methods for improving the column efficiency, such as decreasing the column diameter and/or increasing the column temperature, are presented. In addition, determination of the functionalization uniformity along an OT column by (a) separately measuring the capacities of two halves of the column, (b) measuring the retention factors for several ions in successive 10 cm segments of the column in multiple injections, and (c) measuring the retention variance of a single ion in different segments of the column from a single injection, is discussed.

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Advances in stationary phases for gas chromatography HE Yongrui, QI Meiling 2020, 38 (4):  409-413.  DOI: 10.3724/SP.J.1123.2019.07026 Abstract ( 197 )   HTML ( 5 )   PDF (752KB) ( 113 )   Developing selective stationary phases for gas chromatography (GC) is key to achieving high-resolution separation of analytes in various samples for their GC determinations. With the rapid development of materials science, researches on employing diverse types of materials as GC stationary phases have advanced considerably. This review mainly focuses on the investigation of porous materials, graphene and analogs, truxene-based materials, and triptycene-based materials as stationary phases for GC separations over the past five years, and briefly discusses the related problems and prospects.

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Preparation of reversed-phase/hydrophilic chromatographic stationary phase based on dialdehyde microcrystalline cellulose-functionalized C18 GAO Jie, WU Qi, CHEN Lixiao, LI Hui, DONG Shuqing, LUO Guoying, ZHANG Shusheng, QIU Hongdeng, ZHAO Liang 2020, 38 (4):  414-423.  DOI: 10.3724/SP.J.1123.2019.03009 Abstract ( 90 )   HTML ( 5 )   PDF (7764KB) ( 54 )   A novel reversed/hydrophilic chromatographic stationary phase based on dialdehyde microcrystalline cellulose (DMCC)-functionalized C18 was prepared by covalent bonding between the amino groups of octadecylamine with the aldehyde groups of DMCC, which was used in reversed-phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) modes. The prepared DMCC-functionalized C18 modified silica (C18-DMCC/SiO2) stationary phase exhibited good hydrophobic selectivity and aromatic selectivity by separating alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) in the RPLC mode. Polar compounds, including anilines, phenols, and glycosides were chosen as analytes to evaluate the polar selectivity of this column in the RPLC mode, and the evaluation results were satisfactory compared with the commercial C18 column. Nucleobases were used for evaluating the hydrophilic interaction liquid chromatography performance of the C18-DMCC/SiO2 column. By investigating the impact of organic solvent content on the retention, it could be found that this new stationary phase had the typical characteristics of reversed-phase/hydrophilic chromatography.

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Preparation and chromatographic properties of mixed-mode chromatographic stationary phases modified by imidazole side-group functionalized poly(ionic liquids) WANG Jie, LIU Hong, WU Dan, ZHAO Bihong, SHEN Jiwei, WANG Chaozhan, WEI Yinmao 2020, 38 (4):  424-429.  DOI: 10.3724/SP.J.1123.2019.07029 Abstract ( 75 )   HTML ( 6 )   PDF (831KB) ( 47 )   A novel mixed-mode chromatographic stationary phase was prepared via surface initiated atom transfer radical polymerization using an imidazole side-group functionalized ionic liquid monomer, 1-(4-vinylbenzyl)-3-cyanomethyl bromide. The structure of the stationary phase was characterized by infrared spectroscopy, elemental analysis, and thermogravimetric analysis. The stationary phase showed good separation ability. The retention mechanism of reversed-phase/ion exchange toward solutes on the stationary phase was verified by determining the effect of mobile phase pH on the retention of substances. Compared with octadecylsilyl-bonded silica stationary phase, it is confirmed that the poly(ionic liquid)-modified stationary phase provides π-π interaction toward the retention of the solutes. The results show that the functionalization of imidazole side groups is a feasible method for preparing new ionic liquid stationary phases.

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Preparation and chromatographic evaluation of a polymer-based stationary phase for weak anion-exchange/hydrophilic interaction LOU Xuhua, ZUO Huiying, WANG Yuan, ZHAO Wenjie 2020, 38 (4):  430-437.  DOI: 10.3724/SP.J.1123.2019.08019 Abstract ( 90 )   HTML ( 7 )   PDF (1151KB) ( 46 )   a weak cationic exchange/hydrophilic interaction mixed-mode stationary phase (Sil-PolyCOOH) for high performance liquid chromatography was prepared by bonding polyethylene maleic anhydride to the surface of amino silica gel via a nucleophilic substitution reaction, followed by hydrolysis of the residual maleic anhydride. The new stationary phase material was characterized by solid-state13C nuclear magnetic resonance analysis and ζ-potential measurements. The chromatographic performance and retention mechanism of this stationary phase were evaluated using nucleosides and nucleic bases as probes. The effects of mobile phase composition, ion strength, and pH on the retention factor were investigated. The results show that the retention mechanism of the stationary phase involves both hydrophilic distribution interaction and multiple forces between the host and guests. The stationary phase also showed good separation performance for saccharides, diquat, and paraquat. These results show that the stationary phase has a good application prospect in the separation of polar compounds.

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Preparation and application of quinine-functionalized poly(1-vinylimidazole)-modified silica stationary phase in hydrophilic interaction chromatography ZHOU Hang, CHEN Jia, ZHANG Yingshan, ZHAO Liang, QIU Hongdeng 2020, 38 (4):  438-444.  DOI: 10.3724/SP.J.1123.2019.06008 Abstract ( 91 )   HTML ( 4 )   PDF (959KB) ( 53 )   A quinine-functionalized poly(1-vinylimidazole)-modified hydrophilic silica stationary phase (Sil-PIm-Qn) was prepared by surface radical chain transfer and nucleophilic substitution reactions. Sil-PIm-Qn was characterized by elemental analysis and FT-IR. The chromatographic characteristics of the stationary phase were investigated in the hydrophilic interaction chromatographic (HILIC) mode. The results showed that five amino acids, nine sulfonamides, and ten nucleosides/nucleobases could be successfully separated on this stationary phase, respectively. The retention behavior of the compounds on the column was evaluated under different chromatographic conditions, i. e., for different salt concentrations and acetonitrile contents in the mobile phases. The stability of this column was also investigated, and the relative standard deviation (RSD, n=10) of the retention time of Sil-PIm-Qn was 0.08%-2.30%. Given its simple and green preparation as well as its unique selectivity and high separation efficiency, Sil-PIm-Qn is expected to find widespread application in the separation of hydrophilic compounds, including sulfonamides and nucleosides/nucleobases, in real samples.

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Preparation of difunctional polymer-based cation exchangers and their application in ion chromatography ZHANG Kai, ZHI Mingyu, HE Yi, ZHU Yan, ZENG Xiuqiong, SHOU Dan 2020, 38 (4):  445-451.  DOI: 10.3724/SP.J.1123.2019.07023 Abstract ( 135 )   HTML ( 13 )   PDF (2821KB) ( 82 )   Ion chromatography (IC) is one of the most important means for the separation and analysis of cationic compounds. Research on high-performance cation exchangers is of great significance for the advancement of modern IC techniques. Herein we proposed a newly developed modification method for polymer-based particles, based on thiol-radical-mediated polymerization. Specifically, acrylic acid and maleic anhydride were used as monomers and sodium 2-mercaptoethanesulfonate was used as the thiol modifier to prepare novel difunctional cation exchangers, functionalized with both carboxylic and sulfonic groups. With simple strong acid eluents, typical cations were well separated with good resolution. The retention behaviors of metal cations and organic amines on the cation exchangers were investigated using multiple chromatographic models. The good performances of the cation exchangers were also demonstrated by the gradient separation of ten cations within 24 min. The new method was easy to perform with high efficiency. Additionally, the cation exchange capacities of the cation exchangers were easily modulated by adjusting the initial content of the thiol modifier.

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A polymer resin surface polymerization-based hydroxide-selective anion exchange stationary phase YANG Zhanqiang, LI Zongying, YANG Dehui, ZHANG Feifang, YANG Bingcheng 2020, 38 (4):  452-457.  DOI: 10.3724/SP.J.1123.2019.07031 Abstract ( 114 )   HTML ( 11 )   PDF (3967KB) ( 84 )   A polystyrene-divinylbenzene (PS-DVB) microspheres-based hydroxide-selective anion exchange stationary phase is described. This stationary phase is obtained by the surface polymerization of an allyl glycidyl ether (AGE) and the pendant vinyl groups onto the surface of PS-DVB, followed by open-ring of the epoxy groups using an alkylol amine (abbreviated as P@A-M). Both alkylol amines were compared in terms of separation performance of the stationary phase. Scanning electron microscopy, infrared spectroscopy, and elemental analyses were carried out to characterize the stationary phase. The results indicated that the quaternary amine group was successfully introduced onto the surface of the PS-DVB microspheres, and that there was no obvious change in the physicochemical properties of the resin during the surface polymerization reaction. The P@A-M phase showed high hydroxide-selectivity and good separation performance (resolution>1.5) as well as high running stability (relative standard deviation of retention times<1.13%). The utility of the P@A-M phase was demonstrated by using it for the determination of inorganic anions in the tea.

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Preparation and characterization of polyaniline/graphene-coated anion-exchange chromatographic stationary phase LIU Junwei, SUN Yan, YU Wenhao, WANG Chaowei, LI Zhenxing, SUN Yu’an, ZHANG Shusheng, ZHU Yan 2020, 38 (4):  458-463.  DOI: 10.3724/SP.J.1123.2019.08034 Abstract ( 106 )   HTML ( 5 )   PDF (3112KB) ( 74 )   A polyaniline/graphene (PANI/G) composite was selected as the coating material to prepare a coated anion-exchange chromatographic stationary phase. First, aniline and graphene were used to prepare the PANI/G composite, which was coated onto the surface of poly(styrene-divinylbenzene) (PS-DVB) microspheres by physical absorption. Then, a series of anion-exchange stationary phases with different exchange capacities were obtained by quaternization using the nitrogen atom of polyaniline as the reactive site. The stationary phase was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis (EA). The results revealed that PANI/G was successfully coated onto the surface of PS-DVB and quaternized. The efficiency of the self-fabricated chromatographic column was evaluated by separating conventional anions and organic acids. The PANI/G-coated PS-DVB anion-exchange chromatographic column that was quaternized eight times showed good separation performance for conventional anions and organic acids.

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Preparation and evaluation of diureido bridged β-cyclodextrin-bonded chiral stationary phase by high-performance liquid chromatography SHUANG Yazhou, WANG Hui, ZHANG Tianci, LI Laisheng 2020, 38 (4):  464-475.  DOI: 10.3724/SP.J.1123.2019.08006 Abstract ( 95 )   HTML ( 2 )   PDF (2334KB) ( 45 )   A diureido bridged β-cyclodextrin dimer was synthesized by the reaction of 6-deoxy-6-hydroxyethylamino-β-cyclodextrin with hexamethylene diisocyanate. The dimer was then bonded onto silica to obtain a novel diureido bridged β-cyclodextrin-bonded stationary phase (UBCDP). The structure of diureido bridged stationary phase was characterized by infrared spectroscopy, mass spectrometry, and elemental analysis. By using racemic drugs and pesticides as probes (flavanones, triazoles, and dansylated amino acids), the chromatographic properties of UBCDP were evaluated. The separation mechanism was elucidated by comparison with a single β-cyclodextrin chiral stationary phase (CDCSP). The composition, pH value of the mobile phase and column temperature were optimized. The results showed that the UBCDP can resolve 25 chiral compounds, especially 2'-hydroxyflavanone, hexaconazole and dansyl leucine with high resolutions (Rs, 1.52-4.35), and the larger volume hesperidin could also be separated. This trend was related to the synergistic inclusion of bridged cyclodextrins. CDCSP can separate only a small number of enantiomers with low resolutions. UBCDP exhibited better enantio-separation ability and hence had potential application in chiral drugs and chiral pesticide residues analysis.

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Homogeneous synthesis of cellulose phenylcarbamates and evaluation of their enantioseparation capabilities YIN Chunchun, YANG Tiantian, ZHANG Jinming, ZHANG Jun 2020, 38 (4):  476-483.  DOI: 10.3724/SP.J.1123.2019.08044 Abstract ( 90 )   HTML ( 2 )   PDF (876KB) ( 64 )   Understanding the structure-property relationship of polysaccharide derivatives is of great significance toward the development of novel chiral stationary phases. In this work, we used an ionic liquid, 1-allyl-3-methylimidazolium chloride (AmimCl), as the solvent and introduced phenyl isocyanates with various substituents into cellulose to obtain a series of cellulose phenylcarbamates. The effects of the degree of substitution (DS), as well as the type and position of the substituents, on the chiral separation capability of the cellulose phenylcarbamates were researched in detail. With an increase in the DS, the chiral recognition capability of the cellulose phenylcarbamates improved dramatically for most of the chiral analytes. Fully substituted cellulose phenylcarbamates showed the best enantioseparation capabilities. In addition, the type and position of the substituents on the benzene ring significantly influenced the chiral separation capabilities of the cellulose phenylcarbamates. Cellulose 3-methyl-4-chlorophenylcarbamate, 3,5-dichlorophenylcarbamate, and 2-methyl-5-chlorophenylcarbamate had better chiral recognition capabilities than cellulose 3,5-dimethylphenylcarbamate for some chiral analytes.

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Chiral order inorganic mesoporous silica used as stationary phase in gas chromatography PU Qing, HE Yuyu, YUAN Liming 2020, 38 (4):  484-489.  DOI: 10.3724/SP.J.1123.2019.07032 Abstract ( 88 )   HTML ( 6 )   PDF (4750KB) ( 39 )   Chiral mesoporous materials have widely applications in chiral separation, asymmetric catalysis, and chiral sensing. Chiral order inorganic mesoporous silica (COIMS) is a kind of chiral materials with high order mesoporous structure not containing organic component. Here we report that a COIMS diluted with a polysiloxane OV-1701 was explored as a novel stationary phase for capillary gas chromatography. The COIMS was synthesized from D-phenylalanine chiral source, and its separation properties of the chiral column were investigated. Eight enantiomers including chiral alcohols, dialcohols, esters and amino acid derivative have been resolved on the coated capillary column. In addition, COIMS chiral column also exhibits good selectivity for the separations of linear alkanes and alcohols. This work indicates that the column has the advantages of high temperature resistance and short analysis time, so it has great potential to develop it as a chiral stationary phase at high temperature.