Zhi-guo Shi

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Organization: Wuhan University

Department: Department of Chemistry

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TOPICS

Inorganic Chemistry

Mesoporous Material

Chemicals
References

A simple method for the synthesis of a polar-embedded and polar-endcapped reversed-phase chromatographic packing with low activity of residue silanols

Co-reporter:Hai-yan Liu, Zhi-yong Li, Dan Liu, Ying-Wen Xue, Zhi-guo Shi

Journal of Chromatography A 2016 Volume 1443() pp:175-180

Publication Date(Web):22 April 2016

DOI:10.1016/j.chroma.2016.03.043

•A novel water-compatible ODS material was prepared.•The epoxide addition reaction between WD-60 and 1-octadecanethiol was proposed.•Good acid, basic, and water stability were demonstrated.•It was promising to broaden the application range of ODS.Octadecyl bonded silica (ODS) is the most popular packing for reversed-phase chromatography. However, it generally demonstrates bad resolution for polar analytes because of the residue silanols and its poor stability in aqueous mobile phase. To address the problem, a new reversed-phase packing containing both polar-embedded and polar-endcapped moieties was proposed. It was prepared by a very simple method, in which the epoxide addition reaction of 3-glycidoxypropyltrimethoxysilane with 1-octadecanethiol proceeded simultaneously with the reaction of silane coupling onto silica particles. By controlling the molecular ratio of 3-glycidoxypropyltrimethoxysilane to 1-octadecanethiol higher than 1.0 (1.56 for the present study), both polar-embedded and polar-endcapped moieties were achieved onto the packing. The performance of the packing was evaluated in detail. The results demonstrated that neutral, acidic and basic analytes were well separated on the packing. The column efficiency for phenanthrene was 34,200 theoretical plates per meter. In addition, four nucleotides can be separated in 100% phosphate buffered saline solution with good reproducibility, which indicates the packing has good stability in aqueous mobile phase. Amitriptyline, a typical basic analytes, was eluted out with relatively symmetric peak shape (asymmetry factor of 1.36), which implies that the packing has not suffered from the negative effect of residue silanols significantly. Good stability in buffer solution of pH ranging from 2.0 to 10.0 was also documented for the packing.

Novel mode of liquid-phase microextraction: A magnetic stirrer as the extractant phase holder

Co-reporter:Zhi-Yuan Luo;Hai-Yan Liu

Journal of Separation Science 2016 Volume 39( Issue 2) pp:399-404

Publication Date(Web):

DOI:10.1002/jssc.201500789

In the present study, a novel configuration of liquid-phase microextraction was proposed, in which a magnetic stirrer with a groove was used as the extractant phase holder. It was termed as magnetic stirrer liquid-phase microextraction. In this way, the stability of the organic solvent was much improved under high stirring speed; the extraction efficiency was enhanced due to the enormously enlarged contact area between the organic solvent and aqueous phase. The extraction performance of the magnetic stirrer liquid-phase microextraction was studied using chlorobenzenes as the probe analytes. A wide linearity range (20 pg/mL to 200 ng/mL) with a satisfactory linearity coefficient (r² > 0.998) was obtained. Limits of detection ranged from 9.0 to 12.0 pg/mL. Good reproducibility was achieved with intra- and inter-day relative standard deviations <4.8%. The proposed magnetic stirrer liquid-phase microextraction was simple, environmentally friendly and efficient; compared to single-drop microextraction, it had obvious advantages in terms of reproducibility and extraction efficiency. It is a promising miniaturized liquid-phase technology for real applications.

Preparation, characterization and application of a reversed phase liquid chromatography/hydrophilic interaction chromatography mixed-mode C18-DTT stationary phase

Co-reporter:Qing Wang, Yao Long, Lin Yao, Li Xu, Zhi-Guo Shi, Lanying Xu

Talanta 2016 Volume 146() pp:442-451

Publication Date(Web):1 January 2016

DOI:10.1016/j.talanta.2015.09.009

•A mixed-mode stationary phase, C18-DTT, was prepared via “thiol-ene” click chemistry.•It had both reversed phase and hydrophilic interaction chromatographic properties.•It exhibited good stability and 100% aqueous mobile phase compatibility.•It was suitable for separating a series of polar and non-polar analytes.A mixed-mode chromatographic stationary phase, C18-DTT (dithiothreitol) silica (SiO2) was prepared through “thiol-ene” click chemistry. The obtained material was characterized by fourier transform infrared spectroscope, nitrogen adsorption analysis and contact angle analysis. Chromatographic performance of the C18-DTT was systemically evaluated by studying the effect of acetonitrile content, pH, buffer concentration of the mobile phase and column temperature. It was demonstrated that the novel stationary phase possessed reversed phase liquid chromatography (RPLC)/hydrophilic interaction liquid chromatography (HILIC) mixed-mode property. The stop-flow test revealed that C18-DTT exhibited excellent compatibility with 100% aqueous mobile phase. Additionally, the stability and column-to-column reproducibility of the C18-DTT material were satisfactory, with relative standard deviations of retention factor of the tested analytes (verapamil, fenbufen, guanine, tetrandrine and nicotinic acid) in the range of 1.82–3.72% and 0.85–1.93%, respectively. Finally, the application of C18-DTT column was demonstrated in the separation of non-steroidal anti-inflammatory drugs, aromatic carboxylic acids, alkaloids, nucleo-analytes and polycyclic aromatic hydrocarbons. It had great resolving power in the analysis of various compounds in HILIC and RPLC chromatographic conditions and was a promising RPLC/HILIC mixed-mode stationary phase.

Preparation, characterization and application of N-methylene phosphonic acid chitosan grafted magnesia–zirconia stationary phase

Co-reporter:Qing Wang, Jie Chen, Kun Huang, Xin Zhang, Li Xu, Zhi-guo Shi

Analytica Chimica Acta 2015 Volume 854() pp:191-201

Publication Date(Web):7 January 2015

DOI:10.1016/j.aca.2014.11.022

•N-methylene phosphonic acid chitosan grafted MgO–ZrO2 was prepared.•It exhibited superior HILIC chromatographic performance to the bare MgO–ZrO2.•Monosaccharides, phospholipids and peptides were successfully separated.•It was a promising HILIC stationary phase.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.

A reversed-phase/hydrophilic interaction mixed-mode C18-Diol stationary phase for multiple applications

Co-reporter:Qing Wang, Mao Ye, Li Xu, Zhi-guo Shi

Analytica Chimica Acta 2015 Volume 888() pp:182-190

Publication Date(Web):12 August 2015

DOI:10.1016/j.aca.2015.06.058

•A mixed-mode RPLC/HILIC chromatographic stationary phase, C18-Diol, was synthesized.•C18-Diol was compatible with the pure aqueous mobile phase with excellent stability.•The switch between RPLC and HILIC was easy by adjusting mobile phase constitution.•An online 2D-LC-1C system succeeded in fingerprinting of Lonicera. japonica.•It was suitable for complex sample containing both the polar and nonpolar components.A mixed-mode chromatographic packing material, C18 and diol groups modified silica (C18-Diol), was prepared with controllable hydrophobicity and hydrophilicity. It demonstrated excellent aqueous compatibility and stability in aqueous mobile phase; compared to the traditional C18 column, improved peak shape of basic analytes was also obtained. Additionally, it exhibited both reversed-phase liquid chromatographic (RPLC) and hydrophilic interaction chromatographic (HILIC) performance; the analyte separation scope was thus enlarged, demonstrated by simultaneous separation of twenty acids, bases and neutrals. More interestingly, a novel on-line two-dimensional liquid chromatography on the single column (2D-LC-1C) was established by modifying the high performance liquid chromatographic instrument only with the addition of an extra six-port two-position valve. The early co-eluted components of the extract of Lonicera japonica on the 1st-dimension (RPLC) were collected for the online re-injection to the 2nd-dimension (HILIC) by conveniently varying the mobile phase components. Six more peaks were obtained. The established system was simple, easy operation and low cost, which had advantages in analyzing complicated samples.

Preparation, chromatographic evaluation and application of adenosine 5′-monophosphate modified ZrO2/SiO2 stationary phase in hydrophilic interaction chromatography

Co-reporter:Qing Wang, Zhi-Yuan Luo, Mao Ye, Yu-Zhuo Wang, Li Xu, Zhi-guo Shi, Lanying Xu

Journal of Chromatography A 2015 Volume 1383() pp:58-69

Publication Date(Web):27 February 2015

DOI:10.1016/j.chroma.2015.01.017

•The ZrO2/SiO2 was prepared by LbL self-assembly and sol–gel method.•Enhanced column efficiency and basic stability of ZrO2/SiO2 was obtained.•5′-AMP was used to modify ZrO2/SiO2 via Lewis acid–base interaction.•5′-AMP-ZrO2/SiO2 possessed HILIC property with superior separation ability toward acids.•Multi interactions contributed to the HILIC retention.The zirconia-coated silica (ZrO2/SiO2) material was obtained by coupling layer-by-layer (LbL) self-assembly method and sol–gel technology, to take dual advantages of the suitable porous structure of SiO2 and basic resistance of ZrO2. Adenosine 5′-monophosphate (5′-AMP) was then self-assembled onto ZrO2/SiO2 via Lewis acid–base interaction, generating 5′-AMP-ZrO2/SiO2. The chromatographic properties of 5′-AMP-ZrO2/SiO2 were systemically studied by evaluating the effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the 5′-AMP-ZrO2/SiO2 possessed hydrophilic interaction chromatographic (HILIC) property comprising hydrophilic, hydrogen-bonding, electrostatic and ion-exchange interactions. For basic analytes, the column efficiency of ZrO2/SiO2 and 5′-AMP-ZrO2/SiO2 was superior to the bare ZrO2, and different selectivity was obtained after the introduction of 5′-AMP. For acidic analytes, good resolution was obtained on 5′-AMP-ZrO2/SiO2 while the analysis failed on the bare ZrO2 column owing to strong adsorption. Hence, the proposed 5′-AMP-ZrO2/SiO2 had great potential in analyzing acidic compounds in HILIC mode. It was an extended application of ZrO2 based SP.

Magnetic nanoparticles with hydrophobicity and hydrophilicity for solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

Co-reporter:Shu-Wen Xue, Min-Qiong Tang, Li Xu, Zhi-guo Shi

Journal of Chromatography A 2015 Volume 1411() pp:9-16

Publication Date(Web):11 September 2015

DOI:10.1016/j.chroma.2015.07.104

•Fe3O4–divinylbenzene–SO3− magnetic nanoparticle was prepared via “thiol-ene” click reaction.•The sulfonate groups featured the material excellent aqueous dispersibility.•It was used for PAH extraction from environmental samples.•Satisfactory reproducibility, low LODs and good linearity were obtained.Magnetic nanoparticles (MNPs) featured with divinylbenzene (DVB) and sulfonate functionalities (Fe3O4–DVB–SO3−) were prepared via “thiol-ene” click chemistry. The hydrophobic DVB moieties were dedicated for extraction while the hydrophilic sulfonate groups were designed for dispersing the MNPs in aqueous sample solution. Thus, the specially designed material could ensure operational convenience and improve reproducibility during extraction. The application of the material was demonstrated by the extraction of polycyclic aromatic hydrocarbons (PAHs) from environmental water samples followed by gas chromatography–mass spectrometric analysis. The main factors influencing the extraction, including the type of the desorption solvent, the agitation mode, the amount of MNPs, extraction and desorption time and salt addition in sample solution, were investigated in detail. Under the optimized conditions, the proposed method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations less than 16.5% and 21.2%, and low limits of detection of 1.1 pg mL−1, 0.8 pg mL−1, 1.1 pg mL−1, 1.4 pg mL−1, 0.6 pg mL−1, 2.1 pg mL−1 and 0.7 pg mL−1 for naphthalene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene and pyrene, respectively. The developed method was also successfully used for determination of the PAHs in genuine lake and river environmental water samples by standard addition method. All the studied PAHs were detected in these waters with comparable results by the standard liquid–liquid extraction method. The developed MNPs with dual property of hydrophobicity and hydrophilicity were suitable for the treatment of water samples. The magnetic solid phase extraction based on this material was reliable and convenient. It has great potential in the preconcentration of trace analytes in complex matrix.

Construction of a portable sample preparation device with a magnetic poly(methacrylic acid-co-ethylene dimethacrylate) monolith as the extraction medium and its application in the enrichment of UV filters in water samples

Co-reporter:Jing Li;Li Xu;Qiong-Wei Yu;Ting Zhang;Yan Liu

Journal of Separation Science 2014 Volume 37( Issue 19) pp:2732-2737

Publication Date(Web):

DOI:10.1002/jssc.201400518

A portable sample preparation device with a magnetic polymer monolith as the extraction medium was constructed. The monolith was synthesized by polymerizing methacrylic acid and ethylene dimethacrylate around a cylindrical magnet. In this way, the monolith with a magnetic core could be readily attached to the extraction device by magnetism. The constructed device was evaluated for the enrichment of UV filters in water samples, followed by high-performance liquid chromatographic analysis. The extraction efficiency for the targets was satisfactory with no matrix interference. Good linearities were obtained for the UV filters with the correlation coefficients >0.9986. The limits of detection and quantification for the UV filters were 0.3–0.8 and 1.0–2.4 ng/mL, respectively. The recoveries of the UV filters from the spiked water samples at the concentration of 100 ng/mL were 95.3–101.7%, with relative standard deviations <10%. Accordingly, the proposed portable device was demonstrated to be suitable for on-site simultaneous sampling, purification, and preconcentration within a single step.

Hierarchically macro/mesoporous hybrid silica spheres for fast capture of heavy metal ions

Co-reporter:Zhi-Yong Li, Xiao-Pei Wang, Zhi-Yuan Luo, Ying-Wen Xue, Zhi-Guo Shi

Materials Letters 2014 Volume 128() pp:140-143

Publication Date(Web):1 August 2014

DOI:10.1016/j.matlet.2014.04.103

•Hybrid thiol-silica spheres were fabricated by a one-pot approach.•They possessed interlacing arrays of submicrometer-sized blocks and large macropores.•They were successfully used for the fast capture of heavy metal ions.•It was a fast method for environmental remediation.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.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.

Magnetic solid-phase extraction based on methylcellulose coated-Fe3O4–SiO2–phenyl for HPLC–DAD analysis of sildenafil and its metabolite in biological samples

Co-reporter:Minqiong Tang, Qing Wang, Ming Jiang, Li Xu, Zhi-Guo Shi, Ting Zhang, Yan Liu

Talanta 2014 Volume 130() pp:427-432

Publication Date(Web):1 December 2014

DOI:10.1016/j.talanta.2014.07.006

•MSPE was developed for biological analysis of sildenafil and its metabolite. Methylcellulose was self-assembled on the Fe3O4–SiO2–Ph MNPs.•The Fe3O4–SiO2–Ph–MC showed good dispersibility in aqueous matrix.•Satisfactory reproducibility, low LODs and good linearity were obtained for urine and plasma samples.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 0.41–0.96 ng mL−1 from urine and plasma samples. The proposed material possessed good water compatibility and demonstrated excellent applicability for biological samples.

Investigation on performance of zirconia and magnesia–zirconia stationary phases in hydrophilic interaction chromatography

Co-reporter:Qing Wang, Jing Li, Xin Yang, Li Xu, Zhi-guo Shi, Lan-Ying Xu

Talanta 2014 Volume 129() pp:438-447

Publication Date(Web):1 November 2014

DOI:10.1016/j.talanta.2014.06.016

•The MgO–ZrO2 and bare ZrO2 were used as the HILIC SPs.•Effects of chromatographic parameters on retention were discussed in detail.•Adsorptive interaction was the main retention mechanism for two ZrO2-based columns.•They were suitable to basic analytes separation.•The MgO–ZrO2 column exhibited better chromatographic performance than the ZrO2 one.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.Peak identification: 1. sulfamethazine; 2. sulfamerazine; 3. sulfadiazine; 4. thymine; 5. sulfathiazole; 6. melamine; 7. propranolol.

Fast profiling ecotoxicity and skin permeability of benzophenone ultraviolet filters using biopartitioning micellar chromatography based on penetrable silica spheres

Co-reporter:Chen-ru Yin, Li-yun Ma, Jian-geng Huang, Li Xu, Zhi-guo Shi

Analytica Chimica Acta 2013 Volume 804() pp:321-327

Publication Date(Web):4 December 2013

DOI:10.1016/j.aca.2013.10.040

•BMC based on penetrable ODS to profile ecotoxicity and skin permeability of UV-filters.•Penetrable ODS has macropores and mesopores, enabling low column pressure.•QRARs model was established between log k-log BCF and log k-TR.•It was a fast method for prediction and screening.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 (r2) of the QRARs model between log BCF and log k were 0.9398–0.9753, while r2 between TR and log k 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.

Synthesis of hierarchically macro/meso/microporous carbon spheres and its application in fast rechargeable electric double layer capacitor

Co-reporter:Yi Luan, Ying-Wen Xue, Zhi-Guo Shi

Materials Letters 2012 Volume 88() pp:30-32

Publication Date(Web):1 December 2012

DOI:10.1016/j.matlet.2012.08.046

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.Highlights► Porous carbon sphere possessing hierarchical macro/meso/microporosity was prepared. ► It was used as an electrode for EDLC. ► The capacitance reached ca. 172 F g−1 regardless of cyclic voltammetric scan rate.

Drug delivery devices based on macroporous silica spheres

Co-reporter:Zhi-Guo Shi, Qing-Zhong Guo, Yi-Ting Liu, Yu-Xiu Xiao, Li Xu

Materials Chemistry and Physics 2011 Volume 126(Issue 3) pp:826-831

Publication Date(Web):15 April 2011

DOI:10.1016/j.matchemphys.2010.12.035

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.Research highlights▶ Hierarchically macroporous and mesoporous silicas as drug delivery devices. ▶ The silicas were derivatized with octyl or octadecyl moieties. ▶ High drug loading amount for nimodipine. ▶ Enhanced or sustained release was achieved by surface modification.

Determination of phenols in environmental water samples by two-step liquid-phase microextraction coupled with high performance liquid chromatography

Co-reporter:Ping-Ping Zhang, Zhi-Guo Shi, Yu-Qi Feng

Talanta 2011 Volume 85(Issue 5) pp:2581-2586

Publication Date(Web):15 October 2011

DOI:10.1016/j.talanta.2011.08.021

A new device for magnetic stirring-assisted dispersive liquid–liquid microextraction of UV filters in environmental water samples

Co-reporter:Ping-Ping Zhang, Zhi-Guo Shi, Qiong-Wei Yu, Yu-Qi Feng

Talanta 2011 Volume 83(Issue 5) pp:1711-1715

Publication Date(Web):15 February 2011

DOI:10.1016/j.talanta.2010.11.076

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 0.2–0.8 ng mL−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.

Magnetic solid-phase extraction of hydrophobic analytes in environmental samples by a surface hydrophilic carbon-ferromagnetic nanocomposite

Co-reporter:Li Bai, Bo Mei, Qing-Zhong Guo, Zhi-Guo Shi, Yu-Qi Feng

Journal of Chromatography A 2010 Volume 1217(Issue 47) pp:7331-7336

Publication Date(Web):19 November 2010

DOI:10.1016/j.chroma.2010.09.060

A new sorbent of carbon-ferromagnetic nanocomposite was proposed for the extraction of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. The sorbent was specially designed with a hydrophobic sublayer and a hydrophilic surface, which endows the sorbent some unique features. The former shows high extraction capability for the PAHs and the latter provides benign compatibility with the sample matrix. The sorbent can be easily dispersed in aqueous solutions for extraction and no additional stirring or shaking was necessary to facilitate the dispersion, which may bring operational convenience especially for on-site sampling and extraction. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 10 mg of nanoparticles, 40 mmol/L of sodium chloride, 30 min of extraction time without shaking, hexane as the desorption solvent and 15 min as the desorption–sonication time. The results demonstrate that enrichment factors ranging from 35- to 133-fold were obtained for the analytes. The limits of detection and the limits of quantification are in the range of 0.015–0.335 ng/mL and 0.05–1.14 ng/mL, respectively. Finally, the new sorbent was successfully used for the extraction of PAHs in lake water samples.

Synthesis of penetrable macroporous silica spheres for high-performance liquid chromatography

Co-reporter:Jun-Xia Wei, Zhi-Guo Shi, Fei Chen, Yu-Qi Feng, Qing-Zhong Guo

Journal of Chromatography A 2009 Volume 1216(Issue 44) pp:7388-7393

Publication Date(Web):30 October 2009

DOI:10.1016/j.chroma.2009.04.066

Silica microspheres have been synthesized by phase separation and sol–gel transition coupled with emulsion method. The as-obtained material is characterized by scanning electron microscopy, nitrogen sorption, elemental analysis and particle size distribution measurements. The results demonstrated that the material featured with hierarchically porous structure, possessing both mesopores and penetrable macropores. The mesopores provide large surface area while the macropores traverse the silica particles, which may facilitate fast mass transfer as well as guarantee low backpressure when such materials are used for packed high-performance liquid chromatography (HPLC) column. Therefore, their preliminary applications as HPLC packings in fast separation and low-pressure separation have been attempted in the present study. Benzene, benzaldehyde and benzyl alcohol were separated within two minutes on the silica column at a flow rate of 7 mL min−1. Vitamin E mixtures can also be baseline separated at a high flow rate of 8 mL min−1. In addition, thirteen aromatic hydrocarbons were well separated on the octadecyl-bonded silica (ODS) column. In comparison with a commercial Kromasil ODS column, the pressure of the proposed column is much lower (<1/2) under the same chromatographic conditions, while comparable separation efficiency can be achieved.

Synthesis, characterization and application of magnetic-zirconia nanocomposites

Co-reporter:Qing-Zhong Guo, Bo Mei, Shu-Xiang Zhou, Zhi-Guo Shi, Yu-Qi Feng, Jiang-Yu Wu, Guo-Ping Yan, Liang Li

Journal of Non-Crystalline Solids 2009 Volume 355(16–17) pp:922-925

Publication Date(Web):15 June 2009

DOI:10.1016/j.jnoncrysol.2009.04.030

In the present study, a magnetic-zirconia nanocomposite was successfully synthesized by a single-step co-precipitation method. The as-prepared nanocomposite was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and nitrogen sorption measurements. The ultimate material was found to be Fe3O4–ZrO2 nanoparticles with average diameter of 80 nm, high surface area up to 166 m2/g, and strong magnetic property. The application of this new nanocomposite was herein demonstrated by the adsorption of ethyl methylphosphonic acid, a degradation product of nerve agent in water, followed by mass spectrometry detection. Excellent adsorption could be observed, indicating the as-synthesized material was effective to remove phosphonic acid compound from water. Apart from adsorption, the Fe3O4–ZrO2 nanocomposite is promising in various applications such as catalysis and bioseparation.

A template method for the synthesis of hollow carbon fibers

Co-reporter:Zhi-Guo Shi, Ting Zhang, Lan-Ying Xu, Yu-Qi Feng

Microporous and Mesoporous Materials 2008 Volume 116(1–3) pp:698-700

Publication Date(Web):December 2008

DOI:10.1016/j.micromeso.2008.03.019

For the first time, a hollow carbon fiber (HCF) was prepared via a template method. A polypropylene hollow fiber, which is commercial available and affordable, was used as a template. The resultant HCF was characterized by elemental analysis, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen sorption measurements. The as-synthesized carbon material exhibits similar structure to its template: hollow core and highly porous carbon frameworks. Compared with the traditional pyrolytic technology, the proposed approach is more economical, which facilitates massive production of this type of materials.