Zhi-Guo Shi

Wuhan University, Wu-han-shih, Hubei, China

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Publications (55)165.7 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A hydrophilic stationary phase (SP) was prepared through grafting N-methylene phosphonic acid chitosan on magnesia-zirconia particles (P-CTS-MgO-ZrO2) via Lewis acid-base interaction. The resulting material was characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope and nitrogen adsorption analysis. The chromatographic performance of P-CTS-MgO-ZrO2 was systemically evaluated by studying effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the novel SP provided hydrophilic, electrostatic-repulsion and ion-exchange interactions. Compared to the bare MgO-ZrO2, P-CTS-MgO-ZrO2 exhibited superior peak shape, reasonable resolution and reduced analysis time in separation of basic analytes. Besides, remarkable resolving power of acids, i.e. six non-steroidal anti-inflammatory drugs which failed to be eluted from the bare MgO-ZrO2, was obtained with the theoretical plate number (N/m) of 4653-31313, asymmetry factor <1.21 and the resolution of 1.6-3.4. Finally, P-CTS-MgO-ZrO2 SP was applied to separate monosaccharides, phospholipids and peptides. P-CTS-MgO-ZrO2 was a promising hydrophilic SP for wide applications. Copyright © 2014 Elsevier B.V. All rights reserved.
    Analytica chimica acta. 01/2015; 854C:191-201.
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    ABSTRACT: In the present study, magnetic nanoparticles (MNPs) with phenyl functionalized core and a hydrophilic methylcellulose coating were synthesized. The functionalized MNPs showed excellent dispersibility in aqueous solution and they were applied to magnetic solid phase extraction (MSPE) of sildenafil and its metabolite, desmethyl sildenafil, from human urine and plasma samples followed by high performance liquid chromatographic analysis. The factors that may influence the extraction, including the amount of MNPs, pH and salt concentration of sample solution, extraction and desorption time, and the volume of desorption solvent, were investigated in detail. Under the optimum MSPE conditions, the developed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 8.2% and low limits of detection of 0.41-0.96ngmL(-1) from urine and plasma samples. The proposed material possessed good water compatibility and demonstrated excellent applicability for biological samples.
    Talanta 12/2014; 130C:427-432. · 3.50 Impact Factor
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    ABSTRACT: In the current study, zirconia (ZrO2) and its composite, magnesia-zirconia (MgO-ZrO2), were prepared as the hydrophilic interaction chromatographic (HILIC) stationary phases (SPs). Different experimental variables including water content, pH and buffer concentration in the mobile phase (MP) as well as column temperature were systematically studied to permit an in-depth understanding of the chromatographic properties of the mentioned SPs and to explore the retention mechanism further on. The results were compared with a native SiO2 column. Adsorption was demonstrated as the main retention mechanism on the two ZrO2-based SPs. The transferring of the analytes from the MP to the ZrO2-based SPs was endothermic and high column temperature would facilitate the retention. In addition, the MgO-ZrO2 SP exhibited superior resolution, column efficiency as well as stronger retention in comparison to the bare ZrO2 SP, which demonstrated that the introduction of MgO could improve the structure and properties of the material. In conclusion, MgO-ZrO2 was a promising material for HILIC applications.
    Talanta 11/2014; 129C:438-447. · 3.50 Impact Factor
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    ABSTRACT: Hybrid thiol-silica spheres constructed by interlacing arrays of submicrometer-sized blocks and large macropores were fabricated by a one-pot approach and were successfully used for the fast capture of heavy metal ions with a total capture time of less than 2 min.
    Materials Letters 08/2014; 128:140–143. · 2.27 Impact Factor
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    ABSTRACT: In this work, a tandem reversible addition fragmentation chain transfer (RAFT)/click chemistry method was developed to prepare amide-polystyrene-silica (NHCO-Psty-silica) stationary phase. Styrene was immobilized on amino-silica surface via an azide functionalized RAFT agent in a one-pot procedure. The resultant NHCO-Psty-silica column demonstrates better performance for shielding of residue silanols than traditional ODS column, which was ascertained by Engelhardt test (E test), Tanaka test (T test), Galushko test (G test), and Walters test (W test). Our results showed lower values of silanol activity calculated according to the formula in these standard tests for NHCO-Psty-silica column compared to the ODS column we tested. As a result, the NHCO-Psty-silica is suitable for the separation of basic compounds. The hydrophobic, anion exchanging and π-π interaction of the column toward analytes were also evaluated. Moreover, the NHCO-Psty-silica column also showed excellent stability with pure water as mobile phase.
    Journal of chromatography. A. 05/2014;
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    ABSTRACT: Penetrable silica possesses hierarchical pores, mesopores and penetrable macropores, offering fast mass transfer, satisfactory mechanical strength as well as low column pressure. In the present study, penetrable octadecyl-bonded silica (ODS) was for the first time used as biopartitioning micellar chromatography (BMC) stationary phase to profile ecotoxicity and skin permeability of benzophenone UV-filters. Mobile phase (MP) pH and concentration of polyoxyethylene(23)lauryl ether in the MP were systematically studied. Quantitative retention-activity relationships (QRARs) model was established to correlate retention factors (k) on BMC with bioconcentration factor (BCF) and transdermal rate (TR) of UV-filters. Coefficient of determination (r(2)) of the QRARs model between log BCF and logk were 0.9398-0.9753, while r(2) between TR and logk were 0.7569-0.8434, which demonstrated satisfactory predictive ability of the methodology. It was a powerful tool for fast screening by combining penetrable ODS with BMC, and avoiding column blockage often occurring in BMC.
    Analytica chimica acta 12/2013; 804C:321-327. · 4.31 Impact Factor
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    ABSTRACT: Cytokinins (CKs), a vital family of phytohormones, play important roles in the regulation of shoot and root development. However, the quantification of CKs in plant samples is frequently affected by the complex plant matrix. In the current study, we developed a simple, rapid and efficient hydrophilic interaction chromatography-solid phase extraction (HILIC-SPE) method for CKs purification. CKs were extracted by acetonitrile (ACN) followed by HILIC-SPE (silica as sorbents) purification. The extraction solution of plant samples could be directly applied to HILIC-SPE without solvent evaporation step, which simplified the analysis process. Moreover, with HILIC chromatographic retention mechanism, the hydrophobic co-extracted impurities were efficiently removed. Subsequently, CKs were separated by RPLC, orthogonal to the HILIC pretreatment process, and detected by tandem mass spectrometry. The method exhibits high specificity and recovery yield (>77.0%). Good linearities were obtained for all eight CKs ranging from 0.002 to 100ngmL(-1) with correlation coefficients (r) higher than 0.9927. The limits of detection (LODs, signal/noise=5) for the CKs were between 1.0 and 12.4pgmL(-1). Reproducibility of the method was evaluated by intra-day and inter-day measurements and the results showed that relative standard deviations (RSDs) were less than 10.5%. Employing this method, we successfully quantified six CKs in 20mg Oryza sativa leaves and the method was also successfully applied to Brassica napus (flower and leaves).
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 10/2013; 942-943C:31-36. · 2.78 Impact Factor
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    ABSTRACT: SiO2-TiO2 composite fibers, prepared by electrospinning, were successfully applied to the rapid enrichment of phosphopeptides using a lab-in-syringe approach for the first time. Because of their large surface area, mesoporous structure, extraordinary length and appropriate Lewis acidity, the as-prepared SiO2-TiO2 composite fibers exhibited high selectivity and capacity in the enrichment of phosphopeptides from the digestion mixture of β-casein and bovine serum albumin (BSA), as well as human blood serum and nonfat milk. The targeted phosphopeptides could be easily enriched and detected even when the total amount of β-casein was decreased to only 10 fmol, indicating the high detection sensitivity of this method. In addition, the whole enrichment extraction procedure can be finished in less than 3 min, which can avoid or decrease the degradation of endogenous phosphoproteins by proteases released ex vivo during time-consuming treatments. The developed method is rapid, cost-effective, selective, sensitive, operationally simple, and does not require any harsh conditions and intricate equipment, providing an ideal candidate for the enrichment of phosphopeptides from complex biological samples either in the lab or in the field.
    The Analyst 07/2013; · 4.23 Impact Factor
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    ABSTRACT: In pharmaceutical science, construction of drug delivery system based on various carriers is a great challenge. Here we proposed a new silica carrier for drug delivery. The carrier is characterized by penetrable macropores and large pore volume, which renders it an ideal carrier for drug loading especially for macromolecular drugs. Bovine serum albumin (BSA) and oxaprozin were used as models to investigate its delivery behavior. From the results, it demonstrates that the drug loading capacity is very high (for BSA, it reaches 212.2 wt% [drug/carrier]). It is also found that an ultra-fast release for oxaprozin was achieved on this carrier, indicating the material is suitable for constructing enhanced delivery platform for specific drugs to improve the bioavailability.
    Materials and Manufacturing Processes 05/2013; 28(6). · 1.49 Impact Factor
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    ABSTRACT: Exposed heavy metal ions have led to serious pollution and significant health problems to human beings. To eliminate these ions from the environment, in this study, a remediation method based on recycling magnetic nanoparticles is proposed. Long alkyl chain derivatized magnetic nanoparticles were fabricated, and then dodecyl mercaptan was assembled onto the functional nanoparticles via hydrophobic interaction. Since mercapto moieties can form molecular complex with many heavy metal ions via chelation, the proposed material was used to retrieve these ions from water samples. It is noteworthy that, as dodecyl mercaptan was attached onto the magnetic particles via hydrophobic interaction, it can be easily removed by washing with methanol. As a result, the nanoparticles can be recovered for recycling usage, which would be economical for environmental remediation. The material was characterized by scanning electron microscopy, nitrogen sorption, infrared/Raman spectrometry and elemental analysis. Ag+and Pb2+were used as model analytes to evaluate the effectiveness of the material. It is found that, the maximum adsorption capacities of the particles for Ag+and Pb2+reach 43.6 and 38.2mg/g, respectively.
    Materials and Manufacturing Processes 01/2013; 29(1). · 1.49 Impact Factor
  • Yi Luan, Ying-Wen Xue, Zhi-Guo Shi
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    ABSTRACT: A porous carbon sphere (PCS), which exhibits hierarchical macro/meso/microporosity, is fabricated by nanocasting. The macropores within the PCS are penetrable, fully open and well interconnected, which is admirable for fast mass transfer applications. The carbon has been attempted as a novel electrode material for a fast rechargeable electrochemical double layer capacitor (EDLC). Though the total surface area is only 826 (±2) m2 g−1 and a large quantity of micropores exist, the capacitance of the EDLC can reach 172 (± 3) F g−1 regardless of the cyclic voltammetry scan rate. The macropores within the PCS acted as ion-buffering reservoirs in-situ, which facilitates the accessibility of the mesopores as well as the micropores within the PCS. As a result, unlike traditional microporous carbon material, the micropores in the PCS show no obvious negative effect to the performance of the EDLC. The PCS material is a promising candidate in fast mass transfer applications.
    Materials Letters 12/2012; 88:30–32. · 2.27 Impact Factor
  • Lei Ye, Qing Wang, Jinping Xu, Zhi-Guo Shi, Li Xu
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    ABSTRACT: Restricted-access materials based on non-ionic surfactant-coated dodecyl-functionalized magnetic nanoparticles were prepared and applied to extract steroid hormones from environmental and biological samples. The magnetic nanoparticles were synthesized by co-precipitation, and were functionalized with dodecyltriethoxysilane, giving dodecyl-grafted magnetic nanoparticles (C₁₂-Fe₃O₄). They were further modified with different non-ionic surfactants by self-assembly adsorption. Several types of non-ionic surfactants, Tween-20, 40, 60 and 85, and Span-40, 60 and 80, were investigated as the coatings. Tween surfactants coated C₁₂-Fe₃O₄, named as TW-20 (40, 60, 85)-C₁₂, exhibited good dispersibility in aqueous solution, which was a preferred character in extraction; besides, TW-20-C₁₂ and TW-40-C₁₂ showed good anti-interference ability and satisfactory reproducibility when they were used as magnetic solid-phase extraction (MSPE) sorbents. The factors that may influence the extraction, including the amount of magnetic nanoparticles, extraction and desorption time, the amount of salt addition, the type and volume of desorption solvent, the volume of methanol addition and pH of sample solution, were investigated in detail. High performance liquid chromatography-UV detection was employed for analysis of target analytes (steroid hormone compounds). The developed method was successfully used for the determination of the target analytes in environmental and urine samples. Both tested materials afforded good recovery, satisfactory reproducibility and low limits of detection for environmental samples, which indicates that the materials possessed anti-interference ability. However, compared to TW-40-C₁₂, TW-20-C₁₂ nanoparticles provided better recovery in relatively complex biological samples, which may indicate that the latter one is more appreciated in complex samples.
    Journal of Chromatography A 05/2012; 1244:46-54. · 4.61 Impact Factor
  • Cong Zhang, Jian Li, Li Xu, Zhi-Guo Shi
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    ABSTRACT: In the present study, an immobilized liposome chromatography (ILC) stationary phase based on penetrable silica microspheres was prepared. The silica possessed mesopores and penetrable macropores, which afforded sufficient surface area and fast mass transfer, respectively. Compared with the ILC column based on common porous silica gels, the penetrable silica had larger capacity for liposomes' immobilization, lower backpressure and higher separation efficiency. Twenty-two kinds of drugs were used as tested analytes and their retention behaviors on newly prepared ILC column were investigated in detail. Column temperature and pH of mobile phase were both key factors affecting the retention of solutes. The retention of these drugs on ILC column reflected their permeability in vivo. Furthermore, the methanolic aqueous extracts of three traditional Chinese medicines (TCMs), Radix Liquiritiae, Scutellaria Baicalensis and Flos Sophorae, were screened on this novel ILC column. Effects of column temperature and eluent pH on chromatographic behaviors of components of the TCM methanolic extracts were also studied. Several permeable components can be found, indicating that they are potentially active components in the TCMs. It is also found that the as-prepared ILC column remained stable in at least 1 month and the relative standard deviations of adjusted retention times for solutes were lower than 9.0%. The proposed ILC based on the penetrable silica microspheres is promising for the fast and low-pressure separation, especially for fast screening of permeable compounds and modeling the drug-membrane interaction in vitro. It would be a useful approach to predict the permeability of potential active drugs.
    Journal of Chromatography A 02/2012; 1233:78-84. · 4.61 Impact Factor
  • Ping-Ping Zhang, Zhi-Guo Shi, Yu-Qi Feng
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    ABSTRACT: In this work, a two-step liquid-phase microextraction (LPME) method was presented for the extraction of phenols in environmental water samples. Firstly, the polar phenol in water samples (donor phase) was transferred to 1-octanol (extraction mesophase) by magnetic stirring-assisted LPME. Subsequently, target analytes in the 1-octanol was back extracted into 0.1 mol/L sodium hydroxide solution (acceptor phase) by vortex-assisted LPME. By combination of the two-step LPME, the enrichment factors were multiplied. The main features of this two-step LPME for phenols lie in the following aspects. Firstly, the extraction can be accomplished within relatively short time (ca. 20 min). Secondly, it was compatible with HPLC analysis, avoiding derivatization step that is generally necessary for GC analysis. Thirdly, high enrichment factors (296-954 fold) could be obtained for these analytes. Under the optimized conditions, the linearities were 10-1000, 1-500, 1-500, 5-500 and 1-500 ng/mL for different phenols with all regression coefficients higher than 0.9985. The limits of detection were in the range from 0.3 to 3.0 ng/mL for these analytes. Intra-and inter-day relative standard deviations were below 7.6%, indicating a good precision of the proposed method.
    Talanta 10/2011; 85(5):2581-6. · 3.50 Impact Factor
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    ABSTRACT: In this work, a novel method for the fabrication of magnetic carbon nanotubes based on 'aggregation wrap' was proposed. When carbon nanotubes and magnetic nanoparticles were vortically mixed in a solvent, the magnetic nanoparticles were wrapped into the carbon nanotube bundles that formed during the aggregation process, leading to the formation of magnetic carbon nanotubes. Thus, the resultant material can be separated from the solvent rapidly and conveniently by a magnet. Our investigation demonstrated that the 'aggregation wrap' mechanism for the preparation of magnetic composite is also applicable to other self-aggregated micro/nanomaterials, including graphene, graphite, C(60), etc. To testify the feasibility of the magnetic composites in sample preparation, the resultant magnetic carbon nanotubes were applied as sorbents for magnetic solid-phase extraction (MSPE) of estrogens in milk samples. Under optimized conditions, a rapid, convenient and efficient method for the determination of estrogens in milk samples was established by the combination of MSPE with high-performance liquid chromatography with fluorescence detector. The linearity range of the proposed method was 5-2000 μg/L with correlation coefficients (R) of 0.9983-0.9994. The limit of detection (LOD) for three estrogens ranged from 1.21 to 2.35 μg/L. The intra- and inter-day relative standard deviations (RSDs) were <9.3%. The reproducibility of the MSPE with different batches of magnetic carbon nanotubes was acceptable with RSD values <3.6%.
    Journal of Separation Science 07/2011; 34(18):2498-504. · 2.59 Impact Factor
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    Xi-Tian Peng, Zhi-Guo Shi, Yu-Qi Feng
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    ABSTRACT: A rapid, high throughput and sensitive method was presented for automated determination of cationic surfactants in environmental water samples. The method was based on an automated analysis platform that was composed of on-line polymer monolith microextraction (PMME) and high performance liquid chromatography-mass spectrum (HPLC-MS) with an autosampler. A poly(methacrylic acid-co-ethylene dimethacrylate) (MAA-co-EDMA) monolith was selected as the sorbent for purification and enrichment of cationic surfactants in environmental water samples while a new mixed-mode chromatographic column packed with octyl and sulfonic acid co-bonded silica (OSS) was employed for separation and quantitative determination of cationic surfactants in water samples. By integrating sample preparation, chromatographic separation and MS detection into one automated platform, it makes the whole analysis procedure simple, accurate, and time and labor-saving. Several parameters affecting the extraction performance were investigated. Under the optimized conditions, the proposed method was applied to the analysis of seven cationic surfactants in environmental water samples. Good linearities were obtained for all cationic surfactants with R² larger than 0.9895. The limits of detection were found to be in the range of 15-24 ng/L. The method recoveries of the cationic surfactants spiked in water samples were from 80.5% to 115.1%, with relative standard deviations less than 12.4%.
    Journal of Chromatography A 06/2011; 1218(23):3588-94. · 4.61 Impact Factor
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    ABSTRACT: A new kind of silica materials was proposed as carriers for drug delivery. The materials are characterized by the presence of hierarchical macro/mesopores, penetrable macropores and large pore volumes. The unique structure renders them ideal carriers for efficient and sufficient loading of drugs to establish controlled delivery systems. A series of such materials were synthesized and derivatized with octyl or octadecyl to investigate their drug delivery behavior. Nimodipine, as a model drug, was entrapped into the carriers by repeated soaking, filtration and evaporation. It is found that the drug-loading amount increased with increasing mesopore sizes of the carriers. The loading amount can reach as high as 350 wt% (drug/carrier). The in vitro release studies demonstrate that both enhanced release and sustained release can be achieved on the proposed materials. Moreover, the release speed can be controlled by the macropore sizes and surface characteristics of the materials.
    Materials Chemistry and Physics 04/2011; 126(3):826–831. · 2.07 Impact Factor
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    Li Xu, Zhi-Guo Shi, Yu-Qi Feng
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    ABSTRACT: In this review the focus is on application of porous monoliths to miniaturized extraction of biological analysis, with emphasis on porous monolithic materials and different miniaturized extraction formats. The general approaches used to synthesize organic polymer and silica monolithic materials are highlighted, and their properties and applicability are described and compared. Several extraction formats, including in-tube microextraction, chip-based microextraction, tip-based microextraction, among others, are reviewed in depth.
    Analytical and Bioanalytical Chemistry 04/2011; 399(10):3345-57. · 3.66 Impact Factor
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    ABSTRACT: A new technique of retrieving graphene from aqueous dispersion was proposed in the present study. Two-dimensional planar graphene sheets were immobilized onto silica-coated magnetic microspheres by simple adsorption. The graphene sheets were used as adsorbent material to extract six sulfonamide antibiotics (SAs) from water samples. After extraction, they were conveniently separated from the aqueous dispersion by an external magnetic field. Under the optimal conditions, a rapid and effective determination of SAs in environmental water samples was achieved. The limits of detection for six SAs ranged from 0.09 to 0.16 ng/mL. Good reproducibility was obtained. The relative standard deviations of intra- and inter-day analysis were less than 10.7% and 9.8%, respectively.
    Journal of Chromatography A 03/2011; 1218(10):1353-8. · 4.61 Impact Factor
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    ABSTRACT: A new method based on dispersive liquid-liquid microextraction (DLLME) in combination with high-performance liquid chromatography (HPLC) has been developed for the analysis of UV filters. A specially designed flask, which has two narrow open necks with one of them having a capillary tip, was employed to facilitate the DLLME process. By adopting such a device, the extraction and subsequent phase separation were conveniently achieved. A binary solvent system of water sample and low-density extraction solvent (1-octanol) was used for the DLLME and no disperser solvent was involved. The extraction was accelerated by magnetic agitation of the two phases. After extraction, phase separation of the extraction solvent from the aqueous sample was easily achieved by leaving the extraction system statically for a while. No centrifugation step involving in classical DLLME was necessary. The analyte-enriched phase, floating above the sample solution, was elevated and concentrated into the narrow open tip of the flask by adding pure water into it via the other port, which was withdrawn with a microsyringe for the subsequent HPLC analysis. Under the optimized conditions, the limits of detection for the analytes were in range of 0.2-0.8ngmL(-1) .The linearity ranges were 8-20,000 ng mL(-1) for HB, 7-20,000 ng mL(-1) for DB, 8-10,000 ng mL(-1) for BP and 5-20,000 ng mL(-1) for HMB, respectively. Enrichment factors ranging from 59 to 107 folders were obtained for the analytes. The relative standard deviations (n=3) at a spiked level of 80 ng mL(-1) were between 1.4 and 4.8%. The proposed magnetic stirring-assisted DLLME method was successfully applied to the analysis of lake water samples.
    Talanta 02/2011; 83(5):1711-5. · 3.50 Impact Factor