Ajuan Yu
Zhengzhou University
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Publication
Featured researches published by Ajuan Yu.
Talanta | 2016
Kai Hu; Wenfen Zhang; Huaixia Yang; Yongxia Cui; Jingya Zhang; Wenjie Zhao; Ajuan Yu; Shusheng Zhang
A novel calixarene ionic liquid functionalized silica material was synthesized by the preparation of a new calixarene monomer and its grafting on mercaptopropyl modified silica gel. The material was characterized by infrared spectra, elemental analysis, and thermogravimetric analysis. To explore the retention mechanism of the stationary phase, linear solvation energy relationships (LSER) equation as an effective mathematical model was used. In addition to this, the distinct separation mechanisms were outlined by selected examples of chromatographic separations in the different modes. In reversed-phase liquid chromatography, this new stationary phase presented specific chromatographic performance when evaluated using alkylbenzenes, PAHs and phenols as solutes. Due to the existing polar functional groups, this stationary phase can also be used in hydrophilic interaction chromatography, six nucleosides and four ginsenosides were separated successfully in hydrophilic mode. Furthermore, anions can be separated on the column in anion exchange mode. Thus, this new material was can be applied as a new kind of mixed-mode stationary phase in liquid chromatography, which allows an exceptionally flexible adjustment of retention and selectivity by tuning the experimental conditions.
Journal of Chromatography A | 2014
Jing Lu; Wenfen Zhang; Yanhao Zhang; Wenjie Zhao; Kai Hu; Ajuan Yu; Pu Liu; Yangjie Wu; Shusheng Zhang
In the present paper, a new calix[4]arene derivatized chitosan bonded stationary phase (CCS4) for high performance liquid chromatography (HPLC) was synthesized and characterized. Its chromatographic performance and retention mechanism were evaluated in reversed-phase mode compared with ODS using different solute probes including mono-substituted benzenes, phenols and nucleosides. The results showed that CCS4 stationary phase could provide various interactions with solutes, such as hydrophobic, hydrophilic, π-π, and inclusion interactions. It could perform the mixed-mode separation including RP and HILIC.
Talanta | 2014
Kai Hu; Suxiang Feng; Mingxia Wu; Shuang Wang; Wenjie Zhao; Qiong Jiang; Ajuan Yu; Shusheng Zhang
A new stationary phase for high-performance liquid chromatography was prepared by covalently bonding a V-shape cage heteroatom-bridged calixarene onto silica gel using 3-aminopropyltriethoxysilane as coupling reagent. The structure of the new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Linear solvation energy relationship method was successfully employed to evaluate the new phase with a set of 34 solutes. The retention characteristic of the new phase shows significant similarities with ODS, as well as distinctive features. Multiple mechanisms including hydrophobic, hydrogen bonding, π-π and n-π interaction are involved. The chromatographic behavior of the phase was illustrated by using alkylbenzenes, aromatics positional isomers and flavonoids as probes. Moreover, inorganic anions were individually separated in anion-exchange mode by using the same column. Thus, multi-interaction mechanisms and mixed-mode separation of the new phase can very likely guarantee its excellent chromatographic performance for the analysis of complex samples. The column has been successfully employed for the analysis of clenbuterol in animal urine, and it is demonstrated to be suitable and a competitive alternative analytical method for the determination of clenbuterol.
Journal of Agricultural and Food Chemistry | 2014
Wenfen Zhang; Zhifen Deng; Wenjie Zhao; Ling Guo; Wei Tang; Huifang Du; Lin Lin; Qiong Jiang; Ajuan Yu; Lijun He; Shusheng Zhang
In this paper, a rapid and effective HPLC method, using tetraazacalix[2]arene[2]triazine-modified silica gel (NCSi) as solid-phase extraction (SPE) sorbent, was developed for the purification and determination of trace acrylamide in starchy foodstuffs. The main influence factors of SPE including amount of NCSi sorbent, sample flow rate, and volume and composition of washing solution were investigated and evaluated in the sample pretreatment step. The optimized purification effect was achieved at the sample flow rate of 3 mL/min with 100 mg of NCSi and 2 mL of washing solution (water, 100%). The HPLC separation was carried out on a C18 column (250×4.6 mm i.d., 5 μm) with a mobile phase of methanol/water (10:90, v/v). The linear range of the calibration curve was 4-4000 ng/mL with s correlation coefficient of >0.9999. The intraday and interday RSDs (n=5) of peak areas of acrylamide were 0.22 and 0.90% and the intraday and interday RSDs (n=5) of retention times were 0.50 and 1.63%, respectively. In addition, overall recoveries through the extraction and NCSi-SPE purification ranged from 73.13 to 98%. Compared with the commercial SPE sorbents, NCSi featured excellent selectivity to retain polar and nonpolar interferences in the sample matrices. The improved method was simple, rapid, accurate, and promising for the determination of trace acrylamide in starchy foods with a complex matrix.
Journal of Separation Science | 2012
Kai Hu; Junwei Liu; Chao Tang; Caijuan Wang; Ajuan Yu; Fuyong Wen; Wenjie Zhao; Baoxian Ye; Yangjie Wu; Shusheng Zhang
A new para-tert-butylcalix[4]arene column containing thiadiazole functional groups was prepared and used for the separation of polycyclic aromatic hydrocarbons, phenolic compounds, aromatic amines, benzoic acid and its derivatives by high-performance liquid chromatography (HPLC). The effect of organic modifier content in the mobile phase on retention and selectivity of these compounds were investigated. The results indicate that the stationary phase behaves like reversed-phase packing. However, hydrogen bonding, π-π and inclusion interactions seem to be involved in the separation process. The column has been successfully employed for the analysis of clenbuterol in pork and pig casing; the limit of detection and the limit of quantitation for this method by HPLC-UV detection was 0.03 and 0.097 μg/mL, respectively; the method is demonstrated to be suitable and a competitive alternative analytical method for the determination of clenbuterol.
Journal of Chromatography A | 2017
Wenjie Zhao; Kai Hu; Chenchen Hu; Xiaoyu Wang; Ajuan Yu; Shusheng Zhang
A new stationary phase for high performance liquid chromatography (HPLC) applications based on silica gel microspheres decorated with covalent triazine-based frameworks (CTF-SiO2) composite has been reported here. In this new hybrid material, sheet-like covalent triazine-based frameworks (CTF) were grown onto the supporting silica spheres, in order to achieve improved chromatographic separation and selectivity. The new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance and retention mechanism of the new stationary phase were investigated in reversed-phase mode and compared against standard C18 and cyano-modified silica (CN-SiO2) columns. A variety of different probe molecules were analyzed, including mono-substituted benzenes, polycyclic aromatic hydrocarbons, phenols, anilines and bases. The synergism of triazine and aromatic moieties provided several different retention mechanisms, thus improving the selectivity in the CTF-SiO2 composite. The good column packing properties of the uniform silica microspheres combined with the separation ability of the CTF frameworks make the new CTF-SiO2 material a potentially useful stationary phase for the analysis of complex samples.
Journal of Agricultural and Food Chemistry | 2014
Yanhao Zhang; Xiangyu Tian; Yaxiao Guo; Haibin Li; Ajuan Yu; Zhifen Deng; Barry Baoguo Sun; Shusheng Zhang
In this work, a new open-tubular capillary electrochromatography (OT-CEC) method with the nanolatex-coated column was proposed for the determination of nitrites and nitrates in foodstuffs. The method was simple and repeatable as a result of avoiding the introduction of an electroosmotic flow reverse additive (such as cetyltrimethylammonium chloride) in electrophoretic buffer. The limits of quantitation were 0.89 and 1.05 mg kg⁻¹ for nitrate and nitrite, respectively, whereas the overall recoveries ranged from 94 to 103%. The developed OT-CEC method was successfully applied for 12 samples, and the residue profiles of nitrites and nitrates in hams and sausages were obtained and evaluated.
Journal of Chromatography A | 2013
Ajuan Yu; Dongpo Peng; Kai Hu; Aijuan Cao; Junbiao Chang; Yangjie Wu; Shusheng Zhang
A new 4-ferrocenylbenzoyl chloride-bonded stationary phase (Fc-SiO2) for high performance liquid chromatography (HPLC) was prepared using 3-aminopropyltriethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance and retention mechanism of the new stationary phase were evaluated in reversed-phase (RP) or normal-phase (NP) modes using different solute probes including polycyclic aromatic hydrocarbons (PAHs), mono-substituted benzenes, ferrocenyl derivatives, aromatic amines, pyrazine derivatives, drug intermediate pyrrole isomers and sulfonamides. The results showed that this Fc-SiO2 could provide various interactions for different solutes, such as hydrophobic, hydrogen bonding, π-π, dipole-dipole and charge-transfer interactions. The synergistic effects resulting from cyclopentadienyl (Cp) groups, aromatic ring and amido function in the new material improved the separation selectivity by multiple retention mechanisms. The retention behaviors of the analytes on Fc-SiO2 column were investigated with the assistance of quantum chemistry calculation results using DFT-B3LYP/STO-3G(*) base group.
Talanta | 2016
Lijun Qiao; Xiaohua Zhou; Yanhao Zhang; Ajuan Yu; Kai Hu; Shusheng Zhang; Yangjie Wu
A novel multi-function and mixed-mode stationary phase based on 4-chloro-6-pyrimidinylferrocene modified silica (NFcS) was synthesized and characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Linear solvation energy relationship method was successfully employed to evaluate the new phase with a set of 27 solutes including aromatic and aliphatic compounds. Multiple mechanisms including hydrophobic, π-π, hydrogen-bonding, charge-transfer, acid-base equilibrium and anion-exchange interactions are involved. Based on these interactions, successful separation could be achieved among polycyclic aromatic hydrocarbons, mono-substituted benzenes, aromatic amines, phenols, quinolines, pyridines and nucleosides in reversed-phase (RP) or normal-phase (NP) chromatography. Inorganic anions were also shown to be individually separated in anion-exchange chromatography by using the same column. Moreover, the results here also demonstrated that NFcS based stationary phase could effectively reduce the adverse effect of residual silanol in the separation process. Such stationary phase with characteristics of multi-interaction mechanism and mixed-mode separation is potential for the analysis of complex samples. The NFcS column was successfully employed for the analysis of plant growth regulators in Fruit.
Talanta | 2015
Xiaohua Zhou; Xiaole Li; Aijuan Cao; Qiao Lijun; Ajuan Yu; Shusheng Zhang; Yangjie Wu
A new stationary phase for high-performance liquid chromatography was prepared by covalently bonding N-ferrocenyl(benzoyl)amino-acid esters (L(1)) onto silica gel using 3-aminopropyltriethoxysilane as coupling reagent. The structure of new material was characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic behavior of the phase was illustrated in reversed-phase (RP) and normal-phase (NP) modes using polycyclic aromatic hydrocarbons (PAHs), aromatics positional isomers, amines, 5-nitroimidazoles, organophosphorus pesticides and phenols as probes. Multiple mechanisms including hydrophobic, hydrogen bonding, π-π, dipole-dipole, charge-transfer and acid-base equilibrium interactions are involved. Thus, multi-interaction mechanisms and mixed-mode separation of the new phase can very likely guarantee its excellent chromatographic performance for the analysis of complex samples. The L(1) AminoSil column was successfully employed for the analysis of organophosphorus pesticides in vegetable.