Co-reporter:Xue Xiao, Wentao Wang, Yamin Zhang, Li Jia
Journal of Pharmaceutical and Biomedical Analysis 2017 Volume 140(Volume 140) pp:
Publication Date(Web):5 June 2017
DOI:10.1016/j.jpba.2017.03.014
•Fibrin coated open tubular column was prepared with the aid of thrombin.•The column demonstrated ability to separate variants of mAbs by CEC.•The column showed good repeatability and stability.Monoclonal antibodies (mAbs) are one of the most promising classes of therapeutic protein biopharmaceuticals. However, the complexity of mAbs poses a daunting analytical challenge for heterogeneity characterization of mAbs. In this study, inspired by blood coagulation, we adopted a fibrin coating as a novel stationary phase in open tubular (OT) column for the separation of the mAbs variants by capillary electrochromatography. The fibrin coating was prepared by in situ polymerization of fibrin in the presence of thrombin as a catalyst inside a fused-silica capillary. Scanning electron microscopy and electroosmotic flow measurement were carried out to characterize the fibrin coated OT columns. The average thickness of the fibrin coating was about 1.13 μm. And the EOF of the column was pH-dependent. The electrochromatographic performance of the prepared columns was evaluated by characterization of the variants of three mAbs (cetuximab, trastuzumab and rituximab). The columns demonstrated good repeatability with the run-to-run, day-to-day and column-to-column relative standard deviations of migration times less than 2.42%. The study highlighted the potential of adsorbed proteins as stationary phases for the separation of mAbs variants. Furthermore, the study provided a new platform for characterization of heterogeneity of mAbs in pharmaceutical industry.Download high-res image (128KB)Download full-size image
Co-reporter:Zitao Zhong, Xin Yao, Xiaomei Gao, Li Jia
Analytical Biochemistry 2017 Volume 534(Volume 534) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.ab.2017.07.004
A rapid, convenient and efficient DNA extraction method with no need for toxic agents and centrifugation was reported. A polypropylene microfuge (MF) tube was used as the substrate to immobilize polydopamine (PDA). The prepared PDA-coated MF (PDA@MF) tube was used as a pH-responsive platform for rapid extraction of DNA based on pH-induced charge switch of amino and phenolic hydroxyl groups in PDA coating. The extraction procedure is simple and can be finished in 25 min. The PDA@MF tube was applied for extraction of genomic DNA from foodborne pathogens in milk. The extracted DNA was directly used as template for PCR amplification.
Co-reporter:Xiangdong Ma, Chun Ding, Xin Yao, Li Jia
Analytica Chimica Acta 2016 Volume 929() pp:23-30
Publication Date(Web):27 July 2016
DOI:10.1016/j.aca.2016.04.058
•Ti4+-rPDA@Fe3O4 with rough surface was synthesized by introduction of EG.•The particles demonstrated good selectivity for phosphoproteins based on IMAC.•The adsorption capacity of Ti4+-rPDA@Fe3O4 for κ-Cas was 1105.6 mg g−1.•The particles were successfully applied for isolation of phosphoproteins in milk.The reversible protein phosphorylation is very important in regulating almost all aspects of cell life, while the enrichment of phosphorylated proteins still remains a technical challenge. In this work, polydopamine (PDA) modified magnetic particles with rough surface (rPDA@Fe3O4) were synthesized by introduction of ethylene glycol in aqueous solution. The PDA coating possessing a wealth of catechol hydroxyl groups could serve as an active medium to immobilize titanium ions through the metal-catechol chelation, which makes the fabrication of titanium ions modified rPDA@Fe3O4 particles (Ti4+-rPDA@Fe3O4) simple and very convenient. The spherical Ti4+-rPDA@Fe3O4 particles have a surface area of 37.7 m2 g−1 and superparamagnetism with a saturation magnetization value of 38.4 emu g−1. The amount of Ti element in the particle was measured to be 3.93%. And the particles demonstrated good water dispersibility. The particles were used as adsorbents for capture of phosphorylated proteins and they demonstrated affinity and specificity for phosphorylated proteins due to the specific binding sites (Ti4+). Factors affecting the adsorption of phosphorylated proteins on Ti4+-rPDA@Fe3O4 particles were investigated. The adsorption capacity of Ti4+-rPDA@Fe3O4 particles for κ-casein was 1105.6 mg g−1. Furthermore, the particles were successfully applied to isolate phosphorylated proteins in milk samples, which demonstrated that Ti4+-rPDA@Fe3O4 particles had potential application in selective separation of phosphorylated proteins.Figure optionsDownload full-size imageDownload as PowerPoint slide
Co-reporter:Xiangdong Ma
Journal of Chemical Technology and Biotechnology 2016 Volume 91( Issue 4) pp:892-900
Publication Date(Web):
DOI:10.1002/jctb.4654
Abstract
BACKGROUND
Phosphorylated proteins have attracted widespread attention due to their crucial roles in regulating biological processes. Therefore, development of effective methods for identification and detection of phosphorylated proteins is an indispensable step to understand the roles of protein phosphorylation. The aim of this work is to prepare Ti4+-decorated polydopamine-grafted hybrid magnetic particles (Ti4+-PDA@Fe3O4) for highly efficient and selective separation of phosphorylated proteins.
RESULTS
Ti4+-PDA@Fe3O4 particles were synthesized and characterized. A wealth of hydroxyl groups in PDA enhanced the binding capacity of PDA@Fe3O4 for titanium ions. The selectivity of the particles for phosphorylated proteins relies on the affinity of phosphate groups in phosphorylated proteins to titanium ions on the surface of Ti4+-PDA@Fe3O4. The adsorption capacity of Ti4+-PDA@Fe3O4 for β-casein was 1273.9 mg g-1. The adsorption conditions and selectivity of Ti4+-PDA@Fe3O4 for phosphorylated proteins were studied. The feasibility of Ti4+-PDA@Fe3O4 for separation of phosphorylated proteins from milk was also investigated.
CONCLUSIONS
Ti4+-PDA@Fe3O4 demonstrated highly effective and selective adsorption property for phosphorylated proteins based on immobilized metal affinity chromatography mechanism. The successful isolation of phosphorylated proteins from milk by Ti4+-PDA@Fe3O4 demonstrated that the particles will have promising application prospect in selective separation of phosphorylated proteins. © 2015 Society of Chemical Industry
Co-reporter:Yamin Zhang, Wentao Wang, Xiangdong Ma, Li Jia
Analytical Biochemistry 2016 Volume 512() pp:103-109
Publication Date(Web):1 November 2016
DOI:10.1016/j.ab.2016.08.015
Abstract
Development of a simple method for preparation of stable open tubular (OT) columns for proteins separation by capillary electrochromatography is still challenging. In this work, the titanium oxide (TiO2) nanoparticles coated OT column was successfully prepared for separation of proteins by capillary electrochromatography. The polydopamine (PDA) film was first formed in the inner surface of a fused-silica capillary by the self-polymerization of dopamine under alkaline conditions. Then the TiO2 coating was deposited onto the surface of pre-modified capillary with PDA by a liquid phase deposition process. The plentifully active hydroxyl groups in PDA coating can chelate with Ti4+ to boost the nucleation and growth of TiO2 film. The as-prepared TiO2 coated OT column was characterized by scanning electron microscopy and measurement of electroosmotic flow. Furthermore, the influence of liquid phase deposition time on the TiO2 coating was investigated. The TiO2 coated OT column was used for successful separation of two variants of β-lactoglobulin and eight glycoisoforms of ovalbumin. The column demonstrated good repeatability and stability. The relative standard deviations of migration times of proteins representing run-to-run, day-to-day, and column-to-column were less than 3.7%. Moreover, the application of the column was verified by successful separation of acidic proteins in egg white.
Co-reporter:Yu Wang, Xiangdong Ma, Chun Ding, Li Jia
Analytica Chimica Acta 2015 Volume 862() pp:33-40
Publication Date(Web):3 March 2015
DOI:10.1016/j.aca.2015.01.009
•PDA@Fe3O4 were prepared and applied for efficient extraction of DNA from pathogens.•The DNA capture and release by PDA@Fe3O4 was pH-induced.•The adsorption capacity of PDA@Fe3O4 for DNA was 161 mg g−1.•PDA@Fe3O4 based MSPE was combined with PCR and CE for rapid detection of pathogens.Polydopamine functionalized magnetic nanoparticles (PDA@Fe3O4) were prepared and characterized by transmission electron microscopy, scanning electron microscopy, zeta potential and vibrating sample magnetometry. They were found to enable highly efficient capture of genomic deoxyribonucleic acid (DNA). The adsorption capacity of PDA@Fe3O4 for genomic DNA can reach 161 mg g−1. The extraction protocol used aqueous solutions for DNA binding to and releasing from the surface of the magnetic particles based on the pH inducing the charge switch of amino and phenolic hydroxyl groups on PDA@Fe3O4. The extracted DNA with high quality (A260/A280 = 1.80) can be directly used as templates for polymerase chain reaction (PCR) followed by capillary electrophoresis (CE) analysis. None of the toxic chemical reagents and PCR inhibitors was used throughout the whole procedure. PDA@Fe3O4 based magnetic solid phase extraction (MSPE) method was superior to those using commercial kit and traditional phenol–chloroform extraction methods in yield of DNA. The developed PDA@Fe3O4 based MSPE-PCR-CE method was applied for simultaneous and fast detection of Listeria monocytogenes and Escherichia coli O157:H7 in milk.
Co-reporter:Jia Chen, Yuexin Lin, Li Jia
Journal of Chromatography A 2015 Volume 1388() pp:43-51
Publication Date(Web):3 April 2015
DOI:10.1016/j.chroma.2015.02.032
•PSS–MNPs were prepared by a two-step reaction.•PSS–MNPs were found to enable effective separation of lysozyme from egg white.•The maximum adsorption capacity of PSS–MNPs for lysozyme was 476.2 mg g−1.•The separation process was fast and highly efficient.•The separated lysozyme from egg white demonstrated high purity.Poly(sodium 4-styrenesulfonate) modified magnetic nanoparticles (PSS–MNPs) were successfully synthesized and characterized by transmission electron microscopy, scanning electron microscopy, zeta potential, vibrating sample magnetometry, and Fourier-transform infrared spectrometry. The PSS–MNPs were found to enable effective separation of lysozyme from egg white. The impacts of solution pH, ionic strength, and contact time on the adsorption process were investigated. The adsorption kinetic data were well fitted using a pseudo-second-order kinetic model and the adsorption equilibrium can be reached in 3 min. The adsorption isotherm data could be well described by the Langmuir equation. The maximum adsorption capacity of PSS–MNPs for lysozyme was calculated to be 476.2 mg g−1 according to the Langmuir adsorption isotherm. The fast and efficient adsorption of lysozyme by PSS–MNPs was mainly based on electrostatic interactions between them. The adsorbed lysozyme can be eluted using 20 mM phosphate buffer (pH 7.0) containing 1.0 M NaCl with a recovery of 96%. The extracted lysozyme from egg white demonstrated high purity, retaining about 90.7% of total lysozyme activity.
Co-reporter:Xing Xiao;Wentao Wang;Jia Chen
Journal of Separation Science 2015 Volume 38( Issue 16) pp:2893-2899
Publication Date(Web):
DOI:10.1002/jssc.201500315
The separation and determination of proteins in food is an important aspect in food industry. Inspired by the self-polymerization of dopamine under alkaline conditions and the natural adhesive properties of polydopamine, in this paper, a simple and economical method was developed for the preparation of polydopamine-coated open tubular column, in which ammonium persulfate was used as the source of oxygen to induce and facilitate the polymerization of dopamine to form polydopamine. In comparison with a naked fused-silica capillary, the direction and magnitude of the electro-osmotic flow of the as-prepared polydopamine-coated open tubular column could be manipulated by varying the pH values of background solutions due to the existence of amine and phenolic hydroxyl groups on polydopamine coating. The surface morphology of the polydopamine-coated open tubular column was studied by scanning electron microscopy, and the thickness of polydopamine coating was 106 nm. The performance of the polydopamine-coated open tubular column was validated by analysis of proteins. The relative standard deviations of migration times of proteins representing run-to-run, day-to-day, and column-to-column were less than 3.5%. In addition, the feasibility of the polydopamine-coated open tubular column for real samples was verified by the separation of proteins in chicken egg white and pure milk.
Co-reporter:Jia Chen, Yuexin Lin, Yu Wang, Li Jia
Journal of Chromatography B 2015 Volume 991() pp:59-67
Publication Date(Web):1 June 2015
DOI:10.1016/j.jchromb.2015.04.002
•We prepared PDDA-MPs by three reaction steps.•Bacteria were captured by PDDA-MPs based on electrostatic interactions between them.•A PDDA-MPs-PCR-CE method was developed for sensitive detection of bacteria.•Trace amount of bacteria at 101 cfu mL−1 was detected.Pathogenic bacteria cause significant morbidity and mortality to humans. There is a pressing need to establish a simple and reliable method to detect them. Herein, we show that magnetic particles (MPs) can be functionalized by poly(diallyl dimethylammonium chloride) (PDDA), and the particles (PDDA-MPs) can be utilized as adsorbents for capture of pathogenic bacteria from aqueous solution based on electrostatic interaction. The as-prepared PDDA-MPs were characterized by Fourier-transform infrared spectroscopy, zeta potential, vibrating sample magnetometry, X-ray diffraction spectrometry, scanning electron microscopy, and transmission electron microscopy. The adsorption equilibrium time can be achieved in 3 min. According to the Langmuir adsorption isotherm, the maximum adsorption capacities for E. coli O157:H7 (Gram-negative bacteria) and L. monocytogenes (Gram-positive bacteria) were calculated to be 1.8 × 109 and 3.1 × 109 cfu mg−1, respectively. The bacteria in spiked mineral water (1000 mL) can be completely captured when applying 50 mg of PDDA-MPs and an adsorption time of 5 min. In addition, PDDA-MPs-based magnetic separation method in combination with polymerase chain reaction and capillary electrophoresis allows for rapid detection of 101 cfu mL−1 bacteria.
Co-reporter:Manchen Deng, Yu Wang, Li Jia
Analytica Chimica Acta 2014 Volume 827() pp:47-53
Publication Date(Web):27 May 2014
DOI:10.1016/j.aca.2014.04.018
•MIm-MPs were used as adsorbents for rapid and highly efficient capture of E. coli.•A MIm-MPs-PCR-CE method was developed for sensitive detection of E. coli.•Trace amount of E. coli at 101 cfu mL−1 was detected.Effective bacteria detection and quantification are essential prerequisite for the prevention and treatment of infectious diseases. Herein, we report a method for the detection and quantification of Escherichia coli (E. coli).N-Methylimidazolium modified magnetic particles (MIm-MPs) are synthesized successfully and used as an efficient magnetic material for the isolation and concentration of E. coli. The factors including pH of binding buffer, concentration of elution buffer and elution time which may affect the capture and elution efficiencies are optimized. The linear correlation between bacteria concentration and peak area of polymerase chain reaction (PCR) product analyzed by capillary electrophoresis (CE) is determined. Rapid preconcentration of trace amount of E. coli (101 cfu mL−1) in large volume of aqueous sample (500 mL) is achieved, and the capture efficiency can reach 99%. The quantification of bacteria in large volume of spiked tap water and mineral water samples is realized. The recoveries for different concentrations of E. coli in tap and mineral water samples are in the range between 83% and 93%. The results demonstrate that this MIm-MPs-PCR-CE method can be applied to detect and quantify bacteria in real samples.
Co-reporter:Peiling Yang;Wentao Wang;Xing Xiao
Journal of Separation Science 2014 Volume 37( Issue 15) pp:1911-1918
Publication Date(Web):
DOI:10.1002/jssc.201400309
A simple, easy and economical approach for the preparation of a hybrid carbon/silica monolithic capillary column was described for the first time by using silica monolith as framework in combination with hydrothermal carbonization at 180°C. During the preparation process, formamide was introduced to the reaction solutions to reduce the dissolution rate of monolithic silica skeleton and its optimal concentration was 1.5 M. Fourier transform infrared spectrometry, scanning electron microscopy, energy dispersive X-ray spectrometry, and inverse size exclusion chromatography were carried out to characterize the as-prepared column. The results demonstrated that carbon spheres ranging from 150 to 1000 nm were successfully attached to the surface of silica skeleton. The prepared hybrid carbon/silica column had a permeability of 4.4 × 10−14 m2. Chromatographic performance of the column was evaluated by separation of various compounds including alkylbenzenes, nucleosides and bases, and aromatic acids. The column exhibited an efficiency of 75 000 plates/m for butylbenzene at the optimal linear velocity of 0.23 mm/s. The successful separation of these compounds and the study on mechanism indicated that the column can be applied in mixed-mode chromatography.
Co-reporter:Yu Wang;Manchen Deng
Microchimica Acta 2014 Volume 181( Issue 11-12) pp:1275-1283
Publication Date(Web):2014 August
DOI:10.1007/s00604-014-1250-5
Silica coated magnetic particles functionalized with N-methylimidazolium ion (MIm-MPs) were prepared and characterized by transmission electron microscopy, zeta potential, and vibrating sample magnetometry. They were found to enable effective capture of bacteria as confirmed by TEM imaging of the conjugates. The adsorption capacity of the MIm-MPs for Listeria monocytogenes is 6.22 × 108 cfu mg−1, and their efficiency for capturing Listeria monocytogenes from tap water and mineral water is >98 % when applying 80 mg of MIm-MPs and an adsorption time of 10 min. The MIm-MPs were used to capture bacteria from large volumes of aqueous solutions. A combination of polymerase chain reaction (PCR) with capillary electrophoresis (CE) allows for a quantification of Listeria monocytogenes with a detection limit of 102 cfu mL−1. The whole process takes <4 h which is much less than in case of the traditional plate-counting method which can take several days. Good agreements were obtained between the data obtained by the MIm-MPs-PCR-CE-based method and the plate-counting method.
Co-reporter:Lili Yin;Yuexin Lin
Microchimica Acta 2014 Volume 181( Issue 9-10) pp:957-965
Publication Date(Web):2014 July
DOI:10.1007/s00604-014-1187-8
We show that magnetic nanoparticles can be functionalized with graphene oxide (GO-MNPs) in two reaction steps, and that such nanoparticles can be used as adsorbents for the removal of phthalate esters (PAEs) from water samples. The GO-MNPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, zeta potential, and vibrating sample magnetometer. The impacts of contact time, sample pH, ionic strength and sample volume on the adsorption process were investigated. The maximum adsorption capacity for diethyl phthalate was calculated to be 8.71 mg g−1 according to the Langmuir adsorption isotherm. The adsorption efficiency was tested by removal of PAEs. More than 99 % of the total quantity of PAEs (0.12 mg L−1) in 500 mL real water samples can be removed when GO-MNPs (275–330 mg) were used as an adsorbent. In addition, other species (estriol and fluorene) containing benzene rings were also almost completely removed with the PAEs using GO-MNPs, indicating that GO-MNPs are suitable for the removal of the species containing π-electron system through π-π interactions.
Co-reporter:Manchen Deng, Cheng Jiang, Li Jia
Analytica Chimica Acta 2013 Volume 771() pp:31-36
Publication Date(Web):10 April 2013
DOI:10.1016/j.aca.2013.02.005
N-Methylimidazolium modified magnetic particles (MIm-MPs) were prepared and applied in the solid phase extraction of genomic deoxyribonucleic acid (DNA) from genetically modified soybeans. The adsorption of MIm-MPs for DNA mainly resulted from the strong electrostatic interaction between the positively charged MPs and the negatively charged DNA. The elution of DNA from MPs–DNA conjugates using phosphate buffer resulted from the stronger electrostatic interaction of phosphate ions with MPs than DNA. In the extraction procedure, no harmful reagents (e.g. phenol, chloroform and isopropanol, etc.) used, high yield (10.4 μg DNA per 30 mg sample) and high quality (A260/A280 = 1.82) of DNA can be realized. The as-prepared DNA was used as template for duplex-polymerase chain reaction (PCR) and the PCR products were analyzed by a sieving capillary electrophoresis method. Quick and high quality extraction of DNA template, and fast and high resolution detection of duplex PCR products can be realized using the developed method. No toxic reagents are used throughout the method.Graphical abstractHighlights► The MIm-MPs based MSPE method was developed for extraction of DNA from GM soybeans. ► The method does not use harmful reagents. ► High yield and high quality of DNA are obtained.
Co-reporter:Qiaoli Zhou;Peiling Yang;Xing Xiao
Journal of Separation Science 2013 Volume 36( Issue 9-10) pp:1516-1523
Publication Date(Web):
DOI:10.1002/jssc.201201163
Dopamine is easy to self-polymerize under alkaline conditions and the resultant polydopamine is easy to adhere to the surface of many organic and inorganic materials. Based on the characteristics of dopamine, in this paper, a new polydopamine functionalized monolithic silica column was successfully prepared for performing mixed-mode chromatography. The performance of the column was evaluated by the separation of different types of samples including alkylbenzenes, polycyclic aromatic hydrocarbons, aromatic acids, phenols, and bases. The mechanism for the separation of these compounds was studied and appeared to involve the mixed interactions containing π‒π, hydrophobic, electrostatic, and hydrophilic interactions.
Co-reporter:Peiling Yang, Qiaoli Zhou and Li Jia
Analytical Methods 2013 vol. 5(Issue 12) pp:3074-3081
Publication Date(Web):05 Apr 2013
DOI:10.1039/C3AY40180D
A new mixed-mode hydrophilic interaction/cation exchange monolithic silica stationary phase was prepared by chemical modification of a monolithic silica skeleton by dextran sulfate (DS) using 3-aminopropyl-triethoxysilane as a cross-linking agent. The characteristics of the DS column were evaluated by the separation of various biomolecules including amino acids, nucleosides and bases, nucleotides, and peptides. Good separations for these polar biomolecules were obtained within 11 min on the column using isocratic mode. The investigation for the separation mechanism indicated that strong hydrophilic and electrostatic interactions combined to play a role in the separation of these biomolecules on the DS column.
Co-reporter:Cheng Jiang, Shen Xu, Sheng Zhang, Li Jia
Analytical Biochemistry 2012 Volume 420(Issue 1) pp:20-25
Publication Date(Web):1 January 2012
DOI:10.1016/j.ab.2011.09.004
The high quality of DNA template is one of the key factors to ensure the successful execution of polymerase chain reaction (PCR). Therefore, development of DNA extraction methods is very important. In this work, chitosan modified magnetic particles (MPs) were synthesized and employed for extraction of genomic DNA from genetically modified (GM) soybeans. The extraction protocol used aqueous buffers for DNA binding to and releasing from the surface of the MPs based on the pH inducing the charge switch of amino groups in chitosan modified MPs. The extracted DNA was pure enough (A260/A280 = 1.85) to be directly used as templates for PCR amplification. In addition, the PCR products were separated by capillary electrophoresis for screening of GM organisms. The developed DNA extraction method using chitosan modified MPs was capable of preparation of DNA templates, which were PCR inhibitor free and ready for downstream analysis. The whole process for DNA extraction and detection was preferable to conventional methods (phenol–chloroform extraction, PCR, and gel electrophoresis) due to its simplicity and rapidity as well as its avoiding the use of toxic reagents and PCR inhibitors.
Co-reporter:Shen Xu;Cheng Jiang;Yuexin Lin
Microchimica Acta 2012 Volume 179( Issue 3-4) pp:257-264
Publication Date(Web):2012 November
DOI:10.1007/s00604-012-0894-2
Co-reporter:Jie Chen, Pengfei Zhang, Li Jia
Journal of Chromatography A 2011 Volume 1218(Issue 23) pp:3699-3703
Publication Date(Web):10 June 2011
DOI:10.1016/j.chroma.2011.04.029
The mesopores of a monolithic silica column are very important and useful for chromatographic separation since they can offer sufficiently large surface area. In this paper, a novel method with the assistance of an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate ([bmin]BF4)) was developed for the preparation of a C18-modified monolithic silica column for the first time, in which, the through pores and mesopores were formed simultaneously during the sol–gel reaction. The method is effective to simplify the preparation process of the silica-based monolithic columns. The factors influencing the sol–gel process, including the content of methanol and pH, were studied. The chromatographic performance of the prepared monolithic column was evaluated by the separation of alkylbenzenes.
Co-reporter:Pengfei Zhang, Jie Chen, Li Jia
Journal of Chromatography A 2011 Volume 1218(Issue 22) pp:3459-3465
Publication Date(Web):3 June 2011
DOI:10.1016/j.chroma.2011.03.062
The development of mixed-mode stationary phase to achieve multiple separation capabilities in one column is very important for high performance liquid chromatography. In this paper, a new specific stationary phase based on grafting N-methylimidazolium to a monolithic silica column was successfully prepared for performing capillary liquid chromatography. The characteristics of the column were evaluated by the separation of different types of compounds including inorganic anions, aromatic acids, nucleotides, polycyclic aromatic hydrocarbons, alkylbenzenes, and phenols. The mechanisms for the separation of these compounds were investigated and appeared to involve the mixed interactions including anion-exchange, hydrophilic, π–π, dipole–dipole, and hydrophobic interactions.
Co-reporter:Jinmei Hu;Lili Yin
Journal of Separation Science 2011 Volume 34( Issue 5) pp:565-573
Publication Date(Web):
DOI:10.1002/jssc.201000688
Abstract
A novel and convenient protocol for the preparation of an open-tubular column coated with chitosan–silica hybrid using chitosan and silane-coupling agent (γ-glycidoxy-propyltrimethoxysilane) was developed for CEC, in which, chitosan was covalently bonded to the inner wall of a fused-silica capillary using γ-glycidoxy-propyltrimethoxysilane as a cross-linking agent. The stationary phase was hydrophilic due to the chitosan–silica hybrid with abundant amine and hydroxyl functional groups. The chromatographic characteristics of the column were evaluated by the separation of some organic acids and inorganic anions. The column showed good selectivity for nucleotides, aromatic acids, and inorganic anions. The mechanism for the separation of these compounds was primarily based on the hydrophilic and electrostatic interactions combined with the electrophoretic mechanism. The CEC method on the column for the separation of these compounds was compared with CE method in a bare capillary.
Co-reporter:Qiaoli Zhou;Pengfei Zhang
Journal of Separation Science 2011 Volume 34( Issue 23) pp:3303-3309
Publication Date(Web):
DOI:10.1002/jssc.201100567
Abstract
A polydimethylsiloxane (PDMS)-modified monolithic silica column was prepared for performing reversed-phase capillary liquid chromatography. The prepared PDMS column has a permeability of 6.4×10−14 m2 with a plate height <9.2 μm. Alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) were well separated with the PDMS stationary phase, which exhibited similar selectivity and separation mechanism to that of octadecyl stationary phase. The hydrophobic interactions between the analytes and the PDMS stationary phase mainly play the roles for the separation of alkylbenzenes and PAHs. The characteristics of the PDMS column for the separation of alkylbenzenes and PAHs demonstrated that it would be a promising alternative to the octadecyl column.
Co-reporter:Sheng Zhang, Cheng Jiang, Li Jia
Analytical Biochemistry 2011 Volume 408(Issue 2) pp:284-288
Publication Date(Web):15 January 2011
DOI:10.1016/j.ab.2010.09.022
A method based on non-gel sieving capillary electrophoresis (NGS–CE) with ultraviolet (UV) detection has been developed for the separation of multiplex polymerase chain reaction (PCR) products of three pathogenic bacteria in which hydroxypropylmethylcellulose was used as the sieving medium and dynamic capillary coating. In the method, an ion pair reagent, tetrabutylammonium phosphate (TBAP), was first used in NGS–CE to improve the detection sensitivities and resolutions of DNA fragments. The interaction of TBAP and DNA was proved using the UV spectra of DNA with and without TBAP. Field-enhanced sample injection was used as an on-line preconcentration method to improve the detection sensitivity. The separation of DNA fragments ranging from 100 to 1000 bp was accomplished in 30 min. Three pairs of primers and three PCR products of bacteria were successfully separated in 25 min using the developed method. The intraday relative standard deviations (RSDs) for the migration time and peak area for each PCR product were less than 2.4% (n = 5), and the interday RSDs were less than 6.1% (n = 15).
Co-reporter:Zhiliang Lü, Pengfei Zhang, Li Jia
Journal of Chromatography A 2010 Volume 1217(Issue 30) pp:4958-4964
Publication Date(Web):23 July 2010
DOI:10.1016/j.chroma.2010.05.051
A novel cationic hydrophilic interaction monolithic stationary phase based on the chemical modification of carboxymethyl chitosan (CMCH) to the monolithic silica skeleton using carbodiimide as an activation reagent was prepared for performing capillary liquid chromatography. The amino and hydroxy moieties of CMCH functioned as both the ion-exchange sites and polar providers. The performance of the column was studied by the separation of polar acidic compounds. The chitosan functionalized monolithic silica column showed good selectivity for nucleosides, nucleotides, aromatic acids and aliphatic acids. The mechanism for the separation of these compounds was also studied. The results showed that these compounds were separated primarily based on the hydrophilic interaction mechanism.
Co-reporter:Chaofan Hu;Qingqing Liu ;Sheng Zhang
Journal of Separation Science 2010 Volume 33( Issue 14) pp:2145-2152
Publication Date(Web):
DOI:10.1002/jssc.201000074
Abstract
A sensitive, fast and simple method based on magnetic octadecylsilane particles was developed for the extraction of three fat-soluble vitamins followed by capillary LC (CLC) analysis with UV detection. Magnetic octadecylsilane particles were prepared based on three-step reactions including co-precipitation, sol-gel polymerization and alkylation. The characterization of the prepared product was studied by scanning electron microscope and Fourier-transform infrared spectrometry. The particles were used as magnetic SPE adsorbent for the extraction of fat-soluble vitamins in fruit juice-milk beverage. The extraction condition and efficiency of the particles for fat-soluble vitamins were investigated. By coupling magnetic SPE with capillary LC with UV detection, low concentrations of fat-soluble vitamins in fruit juice-milk beverage can be detected without the interference from other substances in the sample matrix.
Co-reporter:Qingqing Liu;Chaofan Hu
Chromatographia 2010 Volume 72( Issue 1-2) pp:95-100
Publication Date(Web):2010 July
DOI:10.1365/s10337-010-1608-8
A micellar electrokinetic chromatography method was developed for the simultaneous determination of three fat-soluble vitamins with UV detection. Several factors, such as the composition, concentration and pH of the background solution, different additives in the background solution, were optimized. Three on-line concentration methods, namely, sweeping, field-enhanced sample injection and pressure-assisted field-enhanced sample injection (PA-FESI), were utilized to improve the detection sensitivities of the analytes and compared. Of the three methods, PA-FESI can achieve the largest concentration efficiency for the fat-soluble vitamins. In the method, enhancement in the detection sensitivities of fat-soluble vitamins was in the range 42 to 103-fold, as compared to the usual injection method. The PA-FESI was used as an on-line concentration method for the determination of fat-soluble vitamins in multivitamin tablets and vitamin E soft capsules.
Co-reporter:Yu Guan, Cheng Jiang, Chaofan Hu, Li Jia
Talanta 2010 Volume 83(Issue 2) pp:337-343
Publication Date(Web):15 December 2010
DOI:10.1016/j.talanta.2010.09.023
Magnetic silica particles coated with hydroxy-terminated multi-walled carbon nanotubes (MWCNTs–OH) were prepared by sol–gel technology, characterized and used for the convenient, rapid and efficient extraction of several estrogens (including diethylstilbestrol, estrone and estriol) in water followed by sweeping micellar electrokinetic chromatography analysis with UV detection. The results demonstrated that sol–gel technology was a feasible, simple and effective technique for the preparation of MWCNTs–OH functionalized magnetic silica particles. The factors affecting the extraction efficiency of estrogens (the pre-activation of magnetic particles, adsorption time, desorption time and the amount of elution solvent) were carefully investigated. The extraction efficiencies for diethylstilbestrol, estrone and estriol were 95.9%, 93.9%, and 52.4%, respectively, under the optimum conditions. The method detection limits for the three estrogens were less than 0.2 ng mL−1. The developed method was applied for the analysis of tap water, mineral water, Pearl River water and honey.
Co-reporter:Yashun Chen, Jie Chen, Li Jia
Journal of Chromatography A 2009 Volume 1216(Issue 12) pp:2597-2600
Publication Date(Web):20 March 2009
DOI:10.1016/j.chroma.2009.01.058
A novel stationary phase triacontyl-functionalized monolithic silica capillary column was successfully prepared for reversed-phase capillary liquid chromatography. The performance of the monolithic silica capillary column coated with triacontyl chain for the separation of alkylbenzenes, xylene isomers, polycyclic aromatic hydrocarbons, and mixture of α- and β-carotenes was studied, which was compared to that using the monolithic silica capillary column coated with octadecyl chain. The comparison results showed that triacontyl-functionalized monolithic silica capillary column would be a promising media to be used for the separation of isomeric solutes with long chain in reversed-phase capillary liquid chromatography.
Co-reporter:Shujuan Wang ;Deping Chen
Journal of Separation Science 2009 Volume 32( Issue 3) pp:388-393
Publication Date(Web):
DOI:10.1002/jssc.200800494
Abstract
A pressurized CEC (pCEC) method with gradient elution was developed for the analysis of flavonoids in two genetically modified corns and five nongenetically modified corns. The pCEC separation of flavonoids was performed on a monolithic silica-ODS column with UV detection at 270 nm. The effects of the concentration of organic solvent in the mobile phase, pH of the electrolyte buffer, applied voltage, and the gradient elution conditions were evaluated systematically. Gradient elution mode was used as an online concentration method to improve the detection sensitivity of flavonoids. Compared to the conventional injection (0.2 μL), there were 9- to 20-fold improvements in the detection sensitivity at the injection volume of 5 μL without adverse effect on the band broadening and the separation resolution. The LODs for the six flavonoids were in the range of 6.5–46 ng/mL under the gradient elution conditions. The developed gradient pCEC method was applied to evaluate flavonoids in various types of corns. The contents of flavonoids in genetically modified corns and nongenetically modified corns were compared.
Co-reporter:Qingqing Liu;Yaling Liu;Yu Guan
Journal of Separation Science 2009 Volume 32( Issue 7) pp:1011-1017
Publication Date(Web):
DOI:10.1002/jssc.200800598
Abstract
A new online concentration method, namely pressure-assisted field-enhanced sample injection (PA-FESI), was developed and compared with FESI for the analysis of water-soluble vitamins by CZE with UV detection. In PA-FESI, negative voltage and positive pressure were simultaneously applied to initialize PA-FESI. PA-FESI uses the hydrodynamic flow generated by the positive pressure to counterbalance the reverse EOF in the capillary column during electrokinetic sample injection, which allowed a longer injection time than usual FESI mode without compromising the separation efficiency. Using the PA-FESI method, the LODs of the vitamins were at ng/mL level based on the S/N of 3 and the RSDs of migration time and peak area for each vitamin (1 μg/mL) were less than 5.1%. The developed method was applied to the analysis of water-soluble vitamins in corns.
Co-reporter:Hui Xu, Li Jia
Journal of Chromatography B 2009 Volume 877(1–2) pp:13-16
Publication Date(Web):1 January 2009
DOI:10.1016/j.jchromb.2008.11.011
A capillary liquid chromatography (CLC) system with UV/vis detection was coupled with an in-tube solid-phase microextraction (SPME) device for the analysis of fat-soluble vitamins and β-carotene. A monolithic silica-ODS column was used as the extraction medium. An optical-fiber flow cell with a long light path in the UV/vis detector was utilized to further enhance the detection sensitivity. In the in-tube SPME/CLC system, the pre-condition of the extraction column and the effect of the injection volume were investigated. The detection limits (LOD) for the fat-soluble vitamins and β-carotene were in the range from 1.9 to 173 ng/mL based on the signal-to-noise ratio of 3 (S/N = 3). The relative standard deviations of migration time and peak area for each analyte were less than 5.0%. The method was applied to the analysis of fat-soluble vitamins and β-carotene contents in corns.
Co-reporter:Shujuan Wang;Da Xing;Deping Chen;Jingshan Zhao
Journal of Separation Science 2008 Volume 31( Issue 5) pp:859-864
Publication Date(Web):
DOI:10.1002/jssc.200700519
Abstract
A pressurized CEC (pCEC) method was developed for the separation of phytohormones, in which UV absorbance was used as the detector and a monolithic silica-ODS column as the separation column. The parameters (including the concentration of organic solvent in the mobile phase, pH of the electrolyte buffer, applied voltage) affecting the separation resolution were evaluated. Two on-line concentration techniques, namely, solvent gradient zone sharpening effect and field-enhanced sample stacking, were utilized to improve detection sensitivity. The combination of the two techniques proved to be beneficial to enhance the detection sensitivity by enabling the injection of large volumes of samples. Compared to the conventional injection mode, the enhancement in the detection sensitivities of phytohormones using the on-line concentration technique is in the range from 9- to 23-fold. The developed pCEC method was applied to evaluate phytohormones in corns.
Co-reporter:Yaling Liu, Li Jia
Microchemical Journal 2008 Volume 89(Issue 1) pp:72-76
Publication Date(Web):June 2008
DOI:10.1016/j.microc.2007.12.003
A method based on magnetic separation was developed for the extraction of several estrogens (including diethylstilbestrol, estrone and estriol) in water followed by sweeping micellar electrokinetic chromatography (MEKC) analysis with UV detection. Novel magnetic octadecylsilane (ODS) particles were prepared using a silanization method with octadecyl trimethoxysilane as the surface modification reagent of magnetic Fe3O4 particles. Octadecyl trimethoxysilane was covalently immobilized on the magnetic iron oxide particles. The particles were used as the sorbents in the magnetic separation for the extraction of trace amounts of estrogens from water. The extraction condition and efficiency of the particles for the estrogens were investigated. Combining the magnetic ODS particles extraction and sweeping MEKC with UV detection, the estrogens at concentrations as low as ng/mL in water can be detected without interference from other substances in the sample matrix.
Co-reporter:
Analytical Methods (2009-Present) 2013 - vol. 5(Issue 12) pp:
Publication Date(Web):
DOI:10.1039/C3AY40180D
A new mixed-mode hydrophilic interaction/cation exchange monolithic silica stationary phase was prepared by chemical modification of a monolithic silica skeleton by dextran sulfate (DS) using 3-aminopropyl-triethoxysilane as a cross-linking agent. The characteristics of the DS column were evaluated by the separation of various biomolecules including amino acids, nucleosides and bases, nucleotides, and peptides. Good separations for these polar biomolecules were obtained within 11 min on the column using isocratic mode. The investigation for the separation mechanism indicated that strong hydrophilic and electrostatic interactions combined to play a role in the separation of these biomolecules on the DS column.
