Co-reporter:Sheng Tang;Shujuan Liu;Xiaojing Liang;Xiaofen Tang;Xingcai Wu;Yong Guo;Xia Liu
Journal of Separation Science 2015 Volume 38( Issue 12) pp:2046-2052
Publication Date(Web):
DOI:10.1002/jssc.201500115
A novel organic-silica hybrid monolith was prepared through the binding of histidine onto the surface of monolithic matrix for mixed-mode per aqueous and ion-exchange capillary electrochromatography. The imidazolium and amino groups on the surface of the monolithic stationary phase were used to generate an anodic electro-osmotic flow as well as to provide electrostatic interaction sites for the charged compounds at low pH. Typical per aqueous chromatographic behavior was observed in water-rich mobile phases. Various polar and hydrophilic analytes were selected to evaluate the characteristics and chromatographic performance of the obtained monolith. Under per aqueous conditions, the mixed-mode mechanism of hydrophobic and ion-exchange interactions was observed and the resultant monolithic column proved to be very versatile for the efficient separations of these polar and hydrophilic compounds (including amides, nucleosides and nucleotide bases, benzoic acid derivatives, and amino acids) in highly aqueous mobile phases. The successful applications suggested that the histidine-modified organic-silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar and hydrophilic compounds.
Co-reporter:Mingliang Zhang, Jia Chen, Abul K. Mallik, Hongdeng Qiu, Shengxiang Jiang, Hirotaka Ihara
Analytica Chimica Acta 2014 Volume 833() pp:48-55
Publication Date(Web):23 June 2014
DOI:10.1016/j.aca.2014.05.011
•A new diamide-embedded octadecyl stationary phase was prepared.•Excellent hydrophobic and aromatic selectivity.•“Polymeric-C18” chromatographic behavior was found.•Superior shape and planarity selectivity over C18 towards isomeric PAHs.•Carbonyl group and adjacent double C18 chains impacted the retention substantially.A novel branch-type diamide-embedded octadecyl stationary phase was prepared by facile amidation. The preparation of this new phase involves the synthesis of new bifunctional silane ligand and surface modification of spherical silica via anchoring of silane coupling agent. The obtained diamide-embedded octadecyl stationary phase demonstrated excellent hydrophobic selectivity, as well as enhanced shape and planarity selectivity in comparison to commercial polymeric and monomeric C18 phases, respectively, as revealed by the systematic investigation into its liquid chromatographic retention of isomeric polycyclic aromatic hydrocarbons. The applicability of this new stationary phase was further testified by the effective separation of isomeric compounds belong to different chemical classes, including chain isomers of alkylbenzenes, and positional isomers of substituted aromatics. An in-depth analysis of the separation mechanisms other than molecular shape recognition involved in the new stationary phase was performed using a linear solvation energy relationships model and compared with its monoamide and pure C18 counterparts correspondingly. The performance of the new stationary phase in quantitative analysis of phenols from real-world samples was also evaluated.
Co-reporter:Sheng Tang, Shujuan Liu, Yong Guo, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2014 Volume 1357() pp:147-157
Publication Date(Web):29 August 2014
DOI:10.1016/j.chroma.2014.04.037
•The latest advances of ILs in CE and CEC are specifically highlighted.•The recent development of PILs in CE and CEC is first summarized.•ILs and PILs have made significant contributions in the improvement of CE and CEC.•Introduction of ILs and PILs in CE and CEC has good prospects in separation science.•Ongoing studies and future perspectives in these areas are discussed.Ionic liquids (ILs) and polymeric ionic liquids (PILs) with unique and fascinating properties have drawn considerable interest for their use in separation science, especially in chromatographic techniques. In this article, significant contributions of ILs and PILs in the improvement of capillary electrophoresis and capillary electrochromatography are described, and a specific overview of the most relevant examples of their applications in the last five years is also given. Accordingly, some general conclusions and future perspectives in these areas are discussed.
Co-reporter:Na Wang, Yong Guo, Licheng Wang, Xiaojing Liang, Shujuan Liu and Shengxiang Jiang
Analyst 2014 vol. 139(Issue 10) pp:2531-2537
Publication Date(Web):26 Feb 2014
DOI:10.1039/C4AN00039K
In this paper, a kind of aminopropyl imidazole-modified silica sorbent was synthesized and used as a solid-phase extraction (SPE) sorbent for the determination of carboxylic acid compounds and polycyclic aromatic hydrocarbons (PAHs). The resultant aminopropyl imidazole-modified silica sorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA) to ensure the successful binding of aminopropyl imidazole on the surface of silica gel. Then the aminopropyl imidazole-modified silica sorbent served as a SPE sorbent for the enrichment of carboxylic acid compounds and PAHs. The new sorbent exhibited high extraction efficiency towards the tested compounds and the results show that such a sorbent can offer multiple intermolecular interactions: electrostatic, π–π, and hydrophobic interactions. Several parameters affecting the extraction recovery, such as the pH of sample solution, the pH of eluent, the solubility of eluent, the volume of eluent, and sample loading, were also investigated. Under the optimized conditions, the proposed method was applied to the analysis of four carboxylic acid compounds and four PAHs in environmental water samples. Good linearities were obtained for all the tested compounds with R2 larger than 0.9903. The limits of detection were found to be in the range of 0.0065–0.5 μg L−1. The recovery values of spiked river water samples were from 63.2% to 112.3% with relative standard deviations (RSDs) less than 10.1% (n = 4).
Co-reporter:Sheng Tang, Yong Guo, Chunming Xiong, Shujuan Liu, Xia Liu and Shengxiang Jiang
Analyst 2014 vol. 139(Issue 17) pp:4103-4117
Publication Date(Web):12 Jun 2014
DOI:10.1039/C4AN00593G
As an intriguing member of the monolith family, nanoparticle-based monoliths have recently emerged as a new class of promising substrates in analytical sample preparation and separation science because of their many distinct characteristics such as high permeability and readily available tailored surface chemistries. This mini-review article specifically summarizes and highlights the latest major advances in the application of nanoparticle-based monoliths for chromatographic separations during the past three years.
Co-reporter:Xiaojing Liang, Shujuan Liu, Shuai Wang, Yong Guo, Shengxiang Jiang
Journal of Chromatography A 2014 Volume 1357() pp:53-67
Publication Date(Web):29 August 2014
DOI:10.1016/j.chroma.2014.04.039
•Using CNTs as sorbent in different extraction modes has been summarized.•CNTs-based sorbents have been used to extract several of targets.•Modified MWCNTs are more widely sued to achieve the selective adsorption.•CNTs-based extraction technology tends to miniaturization and automation.Carbon nanotubes (CNTs), as an advanced material, have been widely used in various fields since its discovery in 1991. In recent years, as an excellent adsorption material, the pure and modified CNTs are successfully used for the purification and enrichment of food, medicine, environmental samples and so on. In this review, we focus on the detailed description of different CNTs-based extraction modes such as solid-phase extraction (SPE) (including cartridge and disk SPE, dispersive SPE, and μ-SPE) and solid-phase microextraction (SPME) (including fiber SPME, electrosorption-enhanced SPME, stir bar sorptive extraction, needle trap SPME, and hollow fiber SPME).
Co-reporter:Sheng Tang, Shujuan Liu, Haixia Ren, Xiaojing Liang, Hongdeng Qiu, Yong Guo, Xia Liu and Shengxiang Jiang
RSC Advances 2014 vol. 4(Issue 49) pp:25819-25826
Publication Date(Web):29 May 2014
DOI:10.1039/C4RA03460K
A new imidazolium-based organic–silica hybrid monolith by binding the imidazole-1-acetic acid onto the surface of monolithic silica was prepared through a simple route. The obtained monolith exhibited per aqueous capillary electrochromatography (PACEC) characteristics in water-rich mobile phases. A typical per aqueous chromatography behavior was observed for the test solutes (an increase in H2O content resulted in an increase in retention). The effects of water content, pH and ion strength of mobile phase on the retention of test compounds in highly aqueous eluents were investigated in detail. PACEC in itself is a green chromatography mode that makes green capillary electrochromatography possible. Various hydrophilic compounds including amino acids were baseline separated with enhanced resolution of the obtained monolith under PACEC mode. It is evidenced that solutes were retained predominantly by hydrophobic interactions under PACEC conditions. Therefore, PACEC has the potential to replace hydrophilic interaction chromatography and meanwhile it is complementary to the reverse-phase chromatography.
Co-reporter:Mingliang Zhang, Jia Chen, Tongnian Gu, Hongdeng Qiu, Shengxiang Jiang
Talanta 2014 Volume 126() pp:177-184
Publication Date(Web):1 August 2014
DOI:10.1016/j.talanta.2014.03.057
•Two ionic liquid-modified stationary phases with octadecyl chains are prepared.•The stationary phases differ from each other in distribution patterns of the polar groups.•Study of stationary phases via a linear solvation energy relationship mode.•Hydrophobic and aromatic selectivities of these phases are investigated.•Insertion of polar imidazolium moieties into octadecyl groups remarkably impacts the chromatographic behavior.Two new stationary phases modified by alkylimidazoliums were prepared for the first time and characterized. One of the new phases was obtained via monomeric immobilization of octadecylimidazole to γ-chloropropyltrimethoxysilane modified silica to form polar-embedded phase; the other one was prepared by co-immobilization of two silane coupling agents (γ-chloropropyltrichlorosilane and octadecyltrichlorosilane) to silica, followed by quaternization of methylimidazole to form polar-spaced phase. This study was intended to compare the retention characteristics of these two stationary phases using linear solvation energy relationships model, as well as to examine the difference in selectivity by eluting alkylbenzenes, alkylnaphthalenes, condensed-ring and phenylene polynuclear aromatic hydrocarbons on both phases. Different effects of distributions of polar functional group and octadecyl chain were found to impact the chromatographic properties.Novel octadecyl stationary phases differ in distribution of imidazolium group have been prepared for the first time and comparatively evaluated via linear solvation energy relationships (LSER) model.
Co-reporter:Lili Xu;Jing Jia;Juanjuan Feng;Juanshu Liu
Journal of Separation Science 2013 Volume 36( Issue 2) pp:369-375
Publication Date(Web):
DOI:10.1002/jssc.201200644
A polymeric ionic liquid modified stainless steel wire for solid-phase microextraction was reported. Mercaptopropyl-functionalized stainless steel wire that was formed by co-condensation of tetramethoxysilane and 3-mercaptopropyltrimethoxysilane via a sol-gel process, which is followed by in situ surface radical chain-transfer polymerization of 1-vinyl-3-octylimidazolium hexafluorophosphate to result in polymeric ionic liquid modified stainless steel wire. The fiber surface was characterized by field emission scanning electron microscope equipped with energy dispersive X-ray analysis. Coupled with GC, extraction performance of the fiber was tested with phenols and polycyclic aromatic hydrocarbons as model analytes. Effects of extraction and desorption conditions were investigated systematically in our work. RSDs for single-fiber repeatability and fiber-to-fiber reproducibility were less than 7.34 and 16.82%, respectively. The calibration curves were linear in a wide range for all analytes and the detection limits were in the range of 10–60 ng L−1. Two real water samples from the Yellow River and local waterworks were applied to test the as-established solid-phase microextraction–GC method with the recoveries of samples spiked at 10 μg L−1 ranged from 83.35 to 119.24%. The fiber not only exhibited excellent extraction efficiency, but also very good rigidity, stability and durability.
Co-reporter:Sheng Tang, Licheng Wang, Haifeng Han, Hongdeng Qiu, Xia Liu and Shengxiang Jiang
RSC Advances 2013 vol. 3(Issue 21) pp:7894-7901
Publication Date(Web):15 Mar 2013
DOI:10.1039/C3RA40580J
A new mixed-mode organic–silica hybrid monolithic column for capillary electrochromatography was synthesized via a sol–gel process and a following post-modification with 4,4′-dipyridine. Characterization by SEM shows that the hybrid monolith has homogenous macroporous morphology and it is well attached to the inner wall of the capillary. A stable and reversed electroosmotic flow (EOF) was generated at acidic pH due to the pyridinium groups on the surface of the stationary phase. The column performance was evaluated by separating various kinds of compounds, such as polycyclic aromatic hydrocarbons (PAHs), alkylbenzenes, phenols, inorganic anions and organic acids. Multiple retention mechanisms including hydrophobic, π–π and anion-exchange interactions were exhibited at separation of the analytes. The monolithic stationary phase exhibited reversed-phase chromatographic behavior toward neutral solutes. Meanwhile, inorganic anions and organic acids can be separated by the mixed-mode mechanism comprising electrophoresis, hydrophobic and anion-exchange interactions. Good performance and repeatability showed that this new hybrid column can be used in the analysis of various compounds with great prospects.
Co-reporter:Haixia Ren, Xia Liu, Shengxiang Jiang
Journal of Pharmaceutical and Biomedical Analysis 2013 Volumes 78–79() pp:100-104
Publication Date(Web):5 May 2013
DOI:10.1016/j.jpba.2013.02.002
Transient isotachophoresis (tITP), usually performed in CZE, is a useful on-line sample preconcentration technique for high saline samples. However, only a few papers have applied tITP in MEKC especially SDS system. This study compared tITP in MEKC with that in CZE for 3-nitro-tyrosine (NT) analysis in urine. No sample clean-up was required. Self-stacking occurred simultaneously as chloride in urine acted as a leading ion. HEPES–Tris buffer at pH 8.2 was used as a terminating electrolyte and separation buffer. UV detection wavelength was set at 426 nm. Experiments showed that tITP in MEKC exhibited much higher peak efficiency (up to 1 000 000), and improved 4-fold sensitivity, compared with those by tITP in CZE. The limit of detection was 0.07 μM for 3-nitrotyrosine in urine.Graphical abstractThe buffer in MEKC system plays an important role in stacking of an anion in urine. HEPES serves as a terminating electrolyte, and self stacking of nitrotyrosine in urine occurs when voltage is applied. Meanwhile, SDS is concentrated to fulfill the KRF rule. Nitrotyrosine and other component in urine would be enriched in the micelle stack.Highlights► Rapid and direct analysis of 3-nitrotyrosine in urine by MEKC was involved. ► We discussed concentration of an anion in high-salt stacking. ► We provided a new insight into high-salt stacking.
Co-reporter:Haixia Ren, Licheng Wang, Xusheng Wang, Xia Liu, Shengxiang Jiang
Journal of Pharmaceutical and Biomedical Analysis 2013 Volume 77() pp:83-87
Publication Date(Web):15 April 2013
DOI:10.1016/j.jpba.2013.01.015
The ionization constant (pKa) and limiting ionic mobility of 3-chlorotyrosine (CT) and 3-nitrotyrosine (NT) were determined in capillary zone electrophoresis (CZE) in a wide pH range. Measurements were carried out in a poly(ionic liquid) (PIL) modified capillary at a low pH (1.80–4.00) and a bare fused capillary at an upper pH (3.00–11.00). Electrostatic interaction between analytes and inner wall was suppressed dramatically. Furthermore, parameters usually empirically assumed were calculated from a simple theoretical model. Besides pKa and limiting ionic mobility, diameter of the hydrated ion was calculated as well. The former were inserted into the database of Peakmaster software, whose predictions led to satisfactory agreement with experimental runs.Graphical abstractThe dissociation constant (pKa) and limiting mobility of 3-chlorotyrosine (CT) and 3-nitrotyrosine (NT) obtained were inserted into database in Peakmaster, whose prediction led to satisfactory agreement with experimental runs.Highlights► This article reported limiting mobilities and pKa values of 3-nitrotyrosine and 3-chlorotyrosine. ► Once tested the data in Peakmaster 5.2, satisfactory agreement with experimental results was obtained. ► The calculation was improved by a simple theoretical model instead of an empirical assumption usually used.
Co-reporter:Juanjuan Feng, Hongdeng Qiu, Xia Liu, Shengxiang Jiang, Juanjuan Feng
TrAC Trends in Analytical Chemistry 2013 Volume 46() pp:44-58
Publication Date(Web):May 2013
DOI:10.1016/j.trac.2013.01.015
•A review of novel SPME fibers with metal wires as supporting substrates.•Novel SPME fibers prepared by physical, chemical and electrochemical methods.•Lifetimes, desorption conditions and analytical performances of SPME fibers compared.•Novel SPME fibers applied in environmental, food, biological and medicinal analysis.This article gives a brief overview of the most relevant examples of solid-phase microextraction (SPME) fibers with metal wires as substrates, mainly concerning different preparation strategies including physical coating, chemical bonding and some other preparation techniques, which involved various sorbent materials (e.g., polymers, nanomaterials, mesoporous materials, metal-organic frameworks, and ionic liquids).
Co-reporter:Haixia Ren, Hongdeng Qiu, Xiaojing Liang, Xusheng Wang, Shengxiang Jiang
Journal of Chromatography B 2013 Volume 935() pp:75-79
Publication Date(Web):15 September 2013
DOI:10.1016/j.jchromb.2013.07.022
•This article reported salivary levels of bromide, iodide, nitrite, nitrate and thiocyanate.•The strong electroosmotic flow controlled counterflow isotachophoretic stacking was applied to saliva analysis.•Diluting saliva by a high and a low dilution factor was discussed and compared.Under a strong counter-electroosmotic flow, five salivary inorganic anions, bromide, iodide, nitrite, nitrate and thiocyanate were determined by field-amplified sample injection in combination with isotachophoretic stacking. Separation and concentration conditions were investigated. A terminating electrolyte, 5 mM borate, was added in the sample. Under the optimized conditions, Br−, I− and SCN− were concentrated online using 150 mM HCl–Tris buffer at pH 7.8 in a bare fused capillary, providing more than ten thousand of sensitivity enrichment compared with normal injections. The relative standard deviations (RSDs, n = 5) were less than 1% in migration times, 8% in peak areas. Using direct UV detection at 200 nm and 226 nm, the limits of detection (LODs, S/N = 3) were of 0.002–0.01 μM. Unfortunately, NO2− and NO3− could be observed in purified or deionized water. Therefore, a low dilution factor was applied to saliva samples. Due to the matrix effect, samples were injected in a shorter time, and standard addition method was applied to determine all the five inorganic anions in saliva. The RSDs of the migration times and peak areas were in a range of 0.2–0.4% and 3.0–4.0%, respectively. The LODs were 0.2–2.0 μM. The salivary levels of the anions obtained were in accord with the reference data. The external standard method can not be adapted to real samples due to biases caused by electrokinetic injection and errors from high dilutions
Co-reporter:Juanjuan Feng, Min Sun, Xusheng Wang, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2012 Volume 1245() pp:32-38
Publication Date(Web):6 July 2012
DOI:10.1016/j.chroma.2012.05.026
Halogen-based polymeric ionic liquid (PIL) fibers, which have proved efficient for solid-phase microextraction (SPME) of polar compounds, were with very limited fiber lifetimes. In this work, a novel crosslinked PIL sorbent with satisfactory stability and durability was prepared in situ via crosslinking polymerization processes on microstructured-silver coated stainless steel wire. 1,1′-(1,6-Hexanediyl)bis(1-vinylimidazolium) bibromide ionic liquid was synthesized and used as the crosslinking agent, with 1-vinyl-3-octylimidazolium bromide as monomer. Extraction properties of the fiber for polar alcohols in polar aqueous matrix were examined using headspace SPME (HS-SPME) coupled to gas chromatography-flame ionization detection (GC-FID). Under the optimized extraction and desorption conditions, the established method exhibited high extraction capacity. Wide linear ranges were obtained with correlation coefficients (R) ranging from 0.9947 to 0.9999. Limits of detection were in the range of 0.5–20 μg L−1. Compared with the non-crosslinked PIL fiber, the proposed crosslinked PIL fiber was with higher thermal stability and durability and longer lifetime. Four different liquor beverages were analyzed as real samples and good results were obtained.Highlights► Dicationic IL was used as crosslinking agent to prepare copolymeric ILs SPME fiber. ► Durability of fibers was improved greatly by in situ crosslinking polymerization. ► Aliphatic alcohols in liquors were quantified by the HS-SPME–GC method.
Co-reporter:Xiaojing Liang, Shujuan Liu, Xinwang Song, Yangwen Zhu and Shengxiang Jiang
Analyst 2012 vol. 137(Issue 22) pp:5237-5244
Publication Date(Web):10 Sep 2012
DOI:10.1039/C2AN36091H
Graphene oxide (GO) has been layer-by-layer assembled onto silica microspheres to form a GO/SiO2 composite stationary phase. All the characterizations of GO/SiO2 by elemental analysis, Raman spectroscopy and Fourier transformed infrared spectrometry confirmed that with the increase of the assembled layer, GO gradually increases on the silica surface. The chromatographic properties of bare SiO2 and GO/SiO2 with different GO assembled layers show that the amount of GO plays an important role in the separation of analytes. Only the appropriate amount of GO on SiO2 can perform a good chromatographic separation. The comparison between chromatographic performances of bare SiO2 column, GO/SiO2-2 column and C18 commercial column clearly show that GO/SiO2-2 and C18 columns obtained a better separation; GO/SiO2-2 exhibits a large π-electron system and C18 exhibits hydrophobicity. The eluting order, peak width and resolution of analyte on GO/SiO2-2 column was highly dependent on the size of its π-electron system, while on the C18 column the decisive factor is its hydrophobic property.
Co-reporter:Juanjuan Feng, Min Sun, Jubai Li, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2012 Volume 1227() pp:54-59
Publication Date(Web):2 March 2012
DOI:10.1016/j.chroma.2012.01.010
Physical and chemical properties of ionic liquids (ILs) are significantly affected by types of their cations and anions. In this paper, a novel aromatically functional 1-vinyl-3-octylimidazolium 2-naphthalene-sulfonate salt was synthesized through metathesis reaction between 1-vinyl-3-octylimidazolium bromide and sodium 2-naphthalene-sulfonate, and polymerized onto the stainless steel wire in situ via surface radical chain-transfer reaction. Octanol/water distribution coefficient of the ionic liquid was studied and compared with that of 1-vinyl-3-octylimidazolium hexafluorophosphate. Partition coefficients of polycyclic aromatic hydrocarbons (PAHs) on these two polymeric ionic liquids-coated fibers indicated the enhanced hydrophobicity and aromaticity of the target IL. Analytical parameters exhibited high extraction efficiency of the novel fiber. Calibration ranges for several PAHs were from 0.02 to 200 μg L−1. Limits of detection (LODs) were ranged from 0.005 to 0.01 μg L−1. Application reliability of the proposed fiber was also investigated with some phthalate ester plasticizers. LODs were ranged from 0.02 to 0.05 μg L−1. Hair spray and nail polish were used as real samples, and di-n-butyl phthalate and di-(2-ethyl-hexyl) phthalate were quantified with the established method.Highlights► Ionic liquid was aromatically functionalized by anion exchange. ► The proposed ionic liquid was polymerized in situ onto metal wire support. ► The fiber exhibited enhanced hydrophobicity and aromaticity.
Co-reporter:Juanjuan Feng, Min Sun, Lili Xu, Shuai Wang, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2012 Volume 1268() pp:16-21
Publication Date(Web):14 December 2012
DOI:10.1016/j.chroma.2012.10.037
Because of the occurrence of ion exchange between high-ionic-strength solution and anions of polymeric ionic liquids (PILs), PILs based solid-phase microextraction (SPME) fibers were rarely used in direct immersion mode to high-salt-added samples. In this work, a novel double-confined PIL sorbent was prepared by co-polymerization of cation and anion of 1-vinyl-3-octylimidzaolium p-styrenesulfonate (VOIm+SS−). The poly(VOIm+-SS−) was chemically bonded onto functionalized stainless steel wire via surface radical chain-transfer reaction. Stability of poly(VOIm+-SS−) in high-ionic-strength solution was investigated and compared with that of poly(1-vinyl-3-octylimidzaolium benzenesulfonate) (poly(VOIm+BS−)) by elemental analysis of sulfur element, and results turned out that the poly(VOIm+-SS−) was more stable. Coupled to gas chromatography (GC), the poly(VOIm+-SS−) fiber was used to extract three sorts of compounds including anilines, phenols and phthalate esters in aqueous solution. The as-established method showed good linearity, low detection limits, and acceptable repeatability. The direct immersion SPME-GC method was applied to determine the model phthalate esters in bottled mineral water. The determination results were satisfactory.Highlights► Cation and anion of IL were copolymerized in situ on functionalized metal support. ► Stability of the PIL fiber in salted solution was enhanced by copolymerization. ► The copolymerized PILs SPME fiber was successfully used in direct immersion mode.
Co-reporter:Xiaojing Liang;Shuai Wang;Shujuan Liu;Xia Liu
Journal of Separation Science 2012 Volume 35( Issue 16) pp:2003-2009
Publication Date(Web):
DOI:10.1002/jssc.201200258
An octadecylsilane functionalized graphene oxide/silica stationary phase was fabricated by assembling graphene oxide onto the silica particles through an amide bond and subsequent immobilization of octadecylsilane. The chromatographic properties of the stationary phase were investigated by reversed-phase chromatography with alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenolic compounds as the analytes. All the compounds achieved good separation on the column. The comparison between a C18 commercial column and the new stationary phase indicated that the existence of π-electron system of graphene oxide allows π–π interaction between analyte and octadecylsilane functionalized graphene oxide/silica stationary phase except for hydrophobic interaction, while only hydrophobic interaction presented between analyte and C18 commercial column. This suggests that some analytes can be better separated on the octadecylsilane functionalized graphene oxide/silica column.
Co-reporter:Peng Yang, Wen Dan Hou, Hong Deng Qiu, Xia Liu, Sheng Xiang Jiang
Chinese Chemical Letters 2012 Volume 23(Issue 5) pp:615-618
Publication Date(Web):May 2012
DOI:10.1016/j.cclet.2012.02.002
In this work, the quercetin imprinted core–shell microspheres were prepared using silica surface imprinting technique. A simple sol–gel procedure was used for the synthesis of the imprinted materials with 3-aminopropyltriethoxysilane as functional monomer and tetraethyl orthosilicate as crosslinker. The SEM images indicated that the MIPs shell was successfully grafted onto the silica surface. The characteristics of the molecularly imprinted polymers such as capacity, selectivity and absorption dynamic were investigated by rebinding experiments. The results showed that the prepared MIPs had good imprinting effect and adsorption amount of quercetin.
Co-reporter:Peng Yang;HaiXia Ren;Zheng Wei;Xia Liu
Science China Chemistry 2012 Volume 55( Issue 2) pp:277-284
Publication Date(Web):2012 February
DOI:10.1007/s11426-011-4403-y
A simple and rapid method of ionic liquid based dispersive liquid-liquid microextraction (DLLME) combining with high performance liquid chromatography (HPLC) was developed for the analysis of four toxic anilines in flour steamed bread and maize steamed bread. Several possible influential factors such as the type of ionic liquid and disperser solvent, extraction time, sample pH, ionic strength and the volume of ionic liquid and disperser solvent were optimized using single factor experiments and orthogonal array design (OAD) with OA25(54) matrix. Analysis of variance (ANOVA) and percent contribution (PC) were used to investigate the significance of the factors of OAD. Sample pH and ionic strength are statistically demonstrated two chief factors. Under the optimum condition, the method exhibits a good linearity (r2 > 0.99) over the studied range (50–1000 ng g−1) for anilines. The extraction factors and recoveries for the anilines in two kinds of steamed breads ranged between 34.1%–73.3% and 44.3%–95.3%, respectively. The limit of detections (LODs) and limit of quantitations (LOQs) ranged between 10–15 ng g−1 and 30–45 ng g−1.
Co-reporter:Juanjuan Feng, Min Sun, Jubai Li, Xia Liu, Shengxiang Jiang
Analytica Chimica Acta 2011 Volume 701(Issue 2) pp:174-180
Publication Date(Web):9 September 2011
DOI:10.1016/j.aca.2011.05.040
A novel silver-coated solid-phase microextraction fiber was prepared based on electroless plating technique. Good extraction performance of the fiber for model compounds including phthalate esters (dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate and diallyl phthalate) and polycyclic aromatic hydrocarbons (naphthalene, fluorene, phenanthrene, fluoranthene) in aqueous solution was obtained. Under the optimized conditions (extraction temperature, extraction time, ionic strength and desorption temperature), the proposed SPME-GC method showed wide linear ranges with correlation coefficients (R2) ranging from 0.9745 to 0.9984. The limits of detection were at the range of 0.02 to 0.1 μg L−1. Single fiber repeatability and fiber-to-fiber reproducibility as well as stability to acid, alkali and high temperature were studied and the results were all satisfactory. The method was applied successfully to the aqueous extracts of disposable paper cup and instant noodle barrel. Several kinds of analytes were detected and quantified.Graphical abstractA novel silver coated SPME fiber with high extraction efficiency and excellent stability was prepared by a simple electroless plating process. Coupled to GC analysis, the fiber showed wide linear ranges for PAHs and PAEs because of its large surface area and the special physicochemical characteristics of the silver coating. Compared with commercially available fibers and other novel SPME fibers reported lately, the silver-coated fiber kept higher extraction efficiency and lower LODs towards the same analytes.Highlights► Silver metal is used as a novel SPME coating. ► A simple electroless plating method based on the silver mirror reaction is applied in the preparation of the proposed fiber. ► The silver-coated SPME fiber exhibits high extraction efficiency and excellent stability and durability to harsh conditions.
Co-reporter:Juanjuan Feng, Min Sun, Lili Xu, Jubai Li, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2011 Volume 1218(Issue 43) pp:7758-7764
Publication Date(Web):28 October 2011
DOI:10.1016/j.chroma.2011.08.076
Polymeric 1-vinyl-3-octylimidazolium hexafluorophosphate was synthesized in situ on stainless steel wire by surface radical chain-transfer polymerization and used as sensitive coatings in solid-phase microextraction. The outer surface of the stainless steel wire was firstly coated with microstructured silver layer via silver mirror reaction and then functionalized with self-assembled monolayers of 1,8-octanedithiol, which acted as chain transfer agent in the polymerization. Coupled to gas chromatography, extraction performance of the fiber was studied with both headspace and direct-immersion modes using benzene, toluene, ethylbenzene and xylenes (BTEX), phenols and polycyclic aromatic hydrocarbon (PAHs) as model analytes. In combination with the microstructured silver layer, the PIL-coated fiber exhibited high extraction efficiency. Linear ranges for BTEX with headspace mode were in the range of 0.2–1000 μg L−1 for benzene, and 0.1–1000 μg L−1 for toluene, ethylbenzene and xylenes. Limits of detection (LODs) were from 0.02 to 0.05 μg L−1. Wide linear ranges of direct-immersion mode for the extraction of several phenols and PAHs were also obtained with correlation coefficients (R) from 0.9943 to 0.9997. The proposed fiber showed good durability with long lifetime. RSDs of 56 times extraction were still in an acceptable range, from 8.85 to 22.8%.Highlights► A novel polymeric 1-vinyl-3-octylimidazolium hexafluorophosphate-coated SPME fiber was synthesized in situ on stainless steel wire by surface radical chain-transfer polymerization. ► A microstructured silver layer was employed to functionalize the stainless steel wire with self-assembled dithiol. ► The fiber exhibited high extraction efficiency and excellent durability.
Co-reporter:Hongmei Liu, Li Ji, Jubai Li, Shujuan Liu, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2011 Volume 1218(Issue 20) pp:2835-2840
Publication Date(Web):20 May 2011
DOI:10.1016/j.chroma.2011.03.047
Use of metal fibers in solid phase microextraction (SPME) can overcome the fragility drawback of conventional fused-silica ones. However, the surface modification of metal substrates is rather difficult, which largely prevents many mature traditional techniques, such as sol–gel and chemical bonding, being used in fabrication of SPME coating on metal-based fibers. This study demonstrates a protocol to resolve this problem by magnetron sputtering a firm Si interlayer on stainless steel fiber. The Si interlayer was easily modified active group, and attached with a multiwalled carbon nanotubes (MWCNTs) coating using the reported approach. The as-prepared MWCNTs/Si/stainless steel wire fiber not only preserved the excellent SPME behaviors of MWCNTs coatings, but also exhibited a number of advantages including high rigidity, long service life, and good stability at high temperature, in acid and alkali solutions. This new surface modification technique might provide a versatile approach to prepare sorbent coatings on unconfined substrates using traditional methods.
Co-reporter:Juanjuan Feng, Min Sun, Jubai Li, Lili Xu, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2011 Volume 1218(Issue 23) pp:3601-3607
Publication Date(Web):10 June 2011
DOI:10.1016/j.chroma.2011.04.018
In this paper, we introduced a novel and versatile route to prepare solid-phase microextraction coatings on the chemically inert stainless steel wire. Polydopamine films can be created on metallic substrates by an oxidant-induced polymerization and subsequently support various secondary reactions to prepare functional surfaces. In the present work, polydopamine-bioactivated stainless steel wire was successfully modified by nanostructured hydroxyapatite. Extraction performance of the fiber was assessed on several polycyclic aromatic hydrocarbons in water solutions. Extraction mechanism was suggested based on the correlation of partition coefficients and Log Ps. Both aqueous and solid real life samples were used to test the reliability of the solid-phase microextraction-gas chromatography method; some analytes were detected and quantified.
Co-reporter:Jing Li;Haifeng Han;Qing Wang;Xia Liu
Journal of Separation Science 2011 Volume 34( Issue 13) pp:1555-1560
Publication Date(Web):
DOI:10.1002/jssc.201100128
Abstract
A new application of the polymeric ionic liquid (PIL) in capillary electrophoresis is reported. Poly(1-vinyl-3-butylimidazolium bromide) was physically adsorbed on silica capillary as the simple and effective coating for capillary electrophoresis (CE) analysis, in which the PIL is not present in the background electrolyte. The electroosmotic flow (EOF) of the PIL-coated capillary as compared with that of the bare fused-silica capillary shows a different dependence on electrolyte pH values. The EOF is reversed over a wide pH range from 3.0 to 9.0 and shows good repeatability. It is also found that the coated capillary has a good tolerance to some organic solvents, 0.1 M NaOH and 0.1 M HCl. The PIL-coated capillary has been employed in different areas. Both the basic proteins and anionic analytes can be well separated by PIL-coated capillaries in a fast and easy way. The PIL-coated capillary is also able to separate organic acid additives in a grape juice. The results showed that this type of coating provides an alternative to the CE separation of anions and basic proteins.
Co-reporter:Qing Wang;Hongdeng Qiu;Jing Li;Haifeng Han;Xia Liu
Journal of Separation Science 2011 Volume 34( Issue 5) pp:594-600
Publication Date(Web):
DOI:10.1002/jssc.201000686
Abstract
A novel approach based on ionic liquid-single-drop microextraction (IL-SDME) online coupling with capillary electrophoresis (CE) was used to determine a toxic alkaloid – colchicine. The IL-SDME procedure was optimized by extraction solvent, drop volume controlling, sample volume and pH, extraction time, and ionic strength. Under optimum conditions, enrichment factor was as much as 41-fold with a relative standard deviation of 2.8% (n=3). Linear range of response was observed from 1 to 100 μg/mL, with detection limit of 0.25 μg/mL and correlation coefficient (R2) of 0.9994. The extraction of colchicine from spiked Lanzhou lily sample was performed and obtaining good result with an average recovery rate of 102.4 and 98.8% at 5 and 50 μg/mL, respectively. Comparing with the previous methods, IL-SDME-CE is really a convenient, economical, and environmentally benign way for determining colchicine.
Co-reporter:Yabin Zhou;Jing Li;Haifeng Han;Xia Liu
Chemical Papers 2011 Volume 65( Issue 3) pp:267-272
Publication Date(Web):2011 June
DOI:10.2478/s11696-011-0014-5
A novel and easy method for the separation of inorganic anions by capillary electrophoresis using a polymeric ionic liquid (PIL), poly(1-vinyl-3-butylimidazolium bromide) as a background electrolyte modifier has been developed. The PIL has been proved to generate a reversed electroosmotic flow which reduces the analysis time and improves the separation significantly. Effects of the PIL concentration and buffer composition (pH and concentration) were evaluated on basis of the resolution and efficiency of the sample. Under optimum conditions, good separation of six model inorganic anions was achieved with high efficiency and excellent reproducibility within 3 min. The results obtained indicate that the combination of reversed EOF and the association between the analytes and the PIL on the capillary wall or BGE play a prominent role in the separation of anions. Therefore, the PIL presents a useful alternative for the BGE modifier in the study of inorganic anions by CE.
Co-reporter:Hongdeng Qiu;Xiaojing Liang;Min Sun
Analytical and Bioanalytical Chemistry 2011 Volume 399( Issue 10) pp:3307-3322
Publication Date(Web):2011 April
DOI:10.1007/s00216-010-4611-x
Stationary phases are the basis of the development and application of high-performance liquid chromatography (HPLC). In this review we focused on the development of silica-based stationary phases, including the synthesis of silica gel and the application of silica in hydrophilic interaction chromatography (HILIC), reversed-phase liquid chromatography (RPLC), chiral separation chromatography, and ion chromatography. New stationary phases, advances in ionic liquid-modified silica, silica-based core-shell materials, and silica-based monolithic columns for HPLC are introduced separately.
Co-reporter:Jing Li, Haifeng Han, Qing Wang, Xia Liu, Shengxiang Jiang
Analytica Chimica Acta 2010 Volume 674(Issue 2) pp:243-248
Publication Date(Web):3 August 2010
DOI:10.1016/j.aca.2010.06.044
A simple and economical capillary electrophoresis method has been developed for the analysis of four model basic proteins by employing a polymeric ionic liquid (PIL), poly(1-vinyl-3-butylimidazolium) bromide, as the dynamic coating additive. When a small amount of PIL was present in the background electrolyte, a cationic coating on the inner surface of fused-silica capillary was established. These PIL modified capillaries not only generated a stable reversed electroosmotic flow, but also effectively eliminated the wall adsorption of proteins. Several important parameters such as the PIL concentration in the background electrolyte, pH values and concentrations of the background electrolyte were optimized to improve the separation of basic proteins. Consequently, under the optimum conditions, a satisfied separation of basic proteins with peak efficiencies ranging from 247,000 to 540,000 (plates m−1) had been accomplished within 11 min. The run-to-run RSDs (n = 3) of the migration times for the four basic proteins were all less than 0.37%.
Co-reporter:Hongmei Liu, Daoai Wang, Li Ji, Jubai Li, Shujuan Liu, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2010 Volume 1217(Issue 12) pp:1898-1903
Publication Date(Web):19 March 2010
DOI:10.1016/j.chroma.2010.01.080
A novel solid-phase microextraction (SPME) fiber is fabricated through the anodization of Ti wire substrates in an electrolyte containing ethylene glycol and NH4F. By a combination of field emission scanning electron microscope and X-ray photoelectron spectroscope studies, it is shown that perpendicularly orientated and well-aligned TiO2 nanotubes are grown in situ on the Ti wire substrate. The SPME fiber coupled with gas chromatograph (GC) is then used to extract polycyclic aromatic hydrocarbons (PAHs), anilines, phenols, and alkanes from standard and real water samples, and exhibits high selectivity for PAHs. After the optimization of adsorption factors (pH, ionic strength, time and temperature) and desorption factors (time and temperature) of the SPME fiber for PAHs, the limit of detection (LOD) of less than 0.1 μg L−1 is achieved, and the calibration curves are all linear (R2 ≥ 0.9898) in the range from 0.1 to 1000 μg L−1. Beyond that, the SPME fiber has high strength, large surface area, good stability at high temperature and in acid and alkali solutions, and long service life, making it have strong application potentials in the selective extraction of PAHs from complex samples at trace levels.
Co-reporter:Qing Wang, Hongdeng Qiu, Jing Li, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2010 Volume 1217(Issue 33) pp:5434-5439
Publication Date(Web):13 August 2010
DOI:10.1016/j.chroma.2010.06.059
An ionic liquid-based single-drop microextraction (IL-SDME) procedure using IL as an extractant on-line coupled to capillary electrophoresis (CE) is proposed. The method is capable of quantifying trace amounts of phenols in environmental water samples. For the SDME of three phenols, a 2.40 nL IL microdrop was exposed for 10 min to the aqueous sample and then was directly injected into the capillary column for analysis. Extraction parameters such as the extraction time, the IL single-drop volume, pH of the sample solution, ionic strength, volume of the sample solution and the extraction temperature were systematically investigated. Detection limits to three phenols were less than 0.05 μg mL−1, and their calibration curves were all linear (R2 ≥ 0.9994) in the range from 0.05 to 50 μg mL−1. And enrichment factors for three phenols were 156, 107 and 257 without agitation, respectively. This method was then utilized to analyze two real environmental samples from Yellow River and tap water, obtaining satisfactory results. Compared with the usual SDME for CE, IL-SDME–CE is a simple, low-cost, fast and environmentally friendly preconcentration technique.
Co-reporter:Juanjuan Feng, Min Sun, Hongmei Liu, Jubai Li, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2010 Volume 1217(Issue 52) pp:8079-8086
Publication Date(Web):24 December 2010
DOI:10.1016/j.chroma.2010.10.089
A novel solid-phase microextraction fiber based on a stainless steel wire coated with Au nanoparticles was prepared and has been applied, coupled with gas chromatography, to the extraction of aromatic hydrophobic organic chemical pollutants in rainwater and soil extract. The solid-phase microextraction fiber exhibited excellent extraction efficiency and selectivity. Effects of extraction time, extraction temperature, ionic strength, stirring rate and desorption conditions were investigated and optimized. Single fiber repeatability and fiber-to-fiber reproducibility were less than 7.90% and 26.40%, respectively. The calibration curves were linear in a wide range for all analytes. Correlation coefficients ranged from 0.9941 to 0.9993. The as-established SPME-GC method was used successfully to two real natural samples. Recovery of analytes spiked at 10 μg L−1 and 100 μg L−1 ranged from 78.4% to 119.9% and the relative standard deviations were less than 11.3%.
Co-reporter:Xiaojing Liang;Shujuan Liu;Hongmei Liu;Xia Liu
Journal of Separation Science 2010 Volume 33( Issue 21) pp:3304-3312
Publication Date(Web):
DOI:10.1002/jssc.201000379
Abstract
Multi-walled carbon nanotubes (MWCNTs) were layer-by-layer assembled onto silica microspheres to form MWCNTs/SiO2 composites and were characterized by surface analysis, elemental analysis, and contact angle. The composite was used as a stationary phase in HPLC for the separation of many kinds of aromatic compounds. The separation of polycyclic aromatic hydrocarbons (PAHs) affected by the number of MWCNTs layers on SiO2 was investigated. Retention times and resolutions of PAHs were affected by the assembled layer of MWCNTs and the type of organic additive in the mobile phase. When the MWCNTs layer increased to 5 (MWCNTs/SiO2-5), PAHs can be completely separated. Aromatic compounds with different substituents can be well separated when only water was used as the eluent on the MWCNTs/SiO2-5 column. Decreasing the pH of the eluent can increase the retention factors of organic acids. Organic amines can also be separated with acetonitrile as organic additive, which were eluted in the order of the electronic cloud density of their aromatic rings. Comparing the MWCNTs/SiO2-5 column with a commercial HPLC column, it was clearly shown that the commercial column exhibited the characteristic of hydrophobicity, and the MWNCTs/SiO2-5 column exhibited the characteristic of a large π-electron system.
Co-reporter:Jing Li;Haifeng Han;Qing Wang;Xia Liu
Journal of Separation Science 2010 Volume 33( Issue 17-18) pp:2804-2810
Publication Date(Web):
DOI:10.1002/jssc.201000211
Abstract
A CE method for poly(N-vinylimidazole) (PVI)-grafted capillaries by the surface-initiated atom transfer radical polymerization has been developed. The coating was prepared with N-vinylimidazole as the monomer, 2-bromo-2-methyl-N-[3-(triethoxysilyl) propyl] propanamide (BTPAm) as the initiator and CuCl/CuCl2/2,2′-bipyridine as the catalyst and ligand. The direction and magnitude of EOF in the PVI-grafted capillary were investigated in a pH range of 3.0–9.0. The results indicated that the EOF could be modulated by varying the pH value of the buffer and an anodic EOF was obtained at pH values below 6.5. A significant improvement in reproducibility and reduction of EOF appeared on the PVI-grafted capillary when compared with the uncoated capillary. Furthermore, the polymer coated capillaries were applied to the separations of the inorganic anions, organic acids and basic proteins and baseline separations were achieved with short analysis time and high reproducibility.
Co-reporter:Jing Li, Qing Wang, Haifeng Han, Xia Liu, Shengxiang Jiang
Talanta 2010 Volume 82(Issue 1) pp:56-60
Publication Date(Web):30 June 2010
DOI:10.1016/j.talanta.2010.03.057
A simple and reliable co-electroosmotic capillary electrophoresis system for the fast determination of aromatic acids has been developed by employing poly (1-vinyl-3-butylimidazolium bromide) as the background electrolyte modifier. The polymeric ionic liquid was synthesized by the conventional radical polymerization. The reversed electroosmotic flow was obtained by adding a small amount of the polymeric ionic liquid (0.0006%, w/v) to the electrolyte. To further improve the resolution of aromatic acids, conditions including the concentration of polymeric ionic liquid and pH of background electrolytes were optimized. All eight aromatic acids were baseline resolved in one measurement in a short time (less than 3.5 min) under optimized conditions, 100 mM NaH2PO4 buffer containing 0.006% (w/v) polymeric ionic liquid, pH 6.0. Separation efficiencies were in the range from 355,000 to 943,000 (plates/m). Satisfactory reproducibility on the basis of the migration time of analytes was achieved. RSDs (n = 3) were less than 0.33% except the p-aminobenzoic acid (0.9%). The applicability of the present method has been demonstrated for the determination of water-soluble aromatic acids in a common drug for external use.
Co-reporter:Xiaojing Liang, Shuai Wang, Jingang Niu, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2009 Volume 1216(Issue 15) pp:3054-3058
Publication Date(Web):10 April 2009
DOI:10.1016/j.chroma.2009.01.072
A new stationary phase Al2O3/SiO2-10 was prepared and characterized by XPS, XRD, SEM and surface analysis. The anion exchanger properties of this new stationary phase were investigated by the separation of inorganic anions in ion chromatography (IC). pH of the mobile phase, concentration and strength of the Lewis base of the elute, and the organic modifier of the mobile phase strongly affect the separation of inorganic anions, and anion exchange selectivities of the analyte on the new support are significantly different from quaternary ammonium styrene based anion exchangers. The result of separation of inorganic anions shows that the new stationary phase provides excellent column efficiency, well-defined chromatographic peaks and favorable retention times.
Co-reporter:Hongmei Liu, Jubai Li, Xia Liu, Shengxiang Jiang
Talanta 2009 Volume 78(Issue 3) pp:929-935
Publication Date(Web):15 May 2009
DOI:10.1016/j.talanta.2008.12.061
The present work reports on the synthesis of chemically bonded multiwalled carbon nanotubes (MWCNTs)/fused-silica fibers and their use in solid phase microextraction of seven phenols from water samples coupled with gas chromatography (GC). The synthetic strategy was verified by infrared (IR) spectroscopy and field emission scanning electron microscopy. Adsorption factors (pH, ionic strength, stirring rate, adsorption time and temperature) and desorption factors (time and temperature) of the fibers were systematically investigated. Detection limits to seven phenols were less than 0.05 μg L−1, and their calibration curves were all linear (R2 ≥ 0.9984) in the range from 0.05 to 5000 μg L−1. This method was then utilized to analyze two real water samples from Yellow River and sanitary wastewater, resulting in satisfactory results. Compared with normal solid phase materials, this MWCNTs-bonded fused-silica fibers showed a number of advantages: wide linear range and low detection limit for extracting phenols couple with GC, and good stability in acid, alkali, organic solvents and at high temperature.
Co-reporter:Huawei Lu;Huanquan Sun;Xia Liu
Chemical Papers 2009 Volume 63( Issue 3) pp:351-357
Publication Date(Web):2009 June
DOI:10.2478/s11696-009-0019-5
Hollow fibre based liquid phase microextraction (HF-LPME) with high performance liquid chromatography (HPLC) was developed for the determination of alkaloids in Corydalis yanhusuo. Three alkaloids (protopine, tetrahydropalmatine, tetrahydroberberine) were extracted from a 10 mL alkaline sample (donor phase) to an organic phase impregnated in the pores of the hollow fibre, and then, they were extracted to an acidic solution (acceptor phase) in the lumen of the fibre. The extract was determined directly by HPLC. Parameters affecting the HF-LPME include the organic solvent, pH of the donor and the acceptor phase, the extraction time and the stirring speed were investigated systematically. To minimize the error of the injection, palmatine was added as an internal standard (I.S.). Under optimal conditions, calibration curves were obtained in the range of 0.1–1.0 mg L−1 with a reasonable linearity (r2 > 0.993) and the limits of detection (LODs) ranged between 10.0 × 10−3 mg L−1 and 13.7 × 10−3 mg L−1. Additionally, enrichment factors with 100 to 184-fold were obtained. The method was then applied to the crude extract of Corydalis yanhusuo successfully.
Co-reporter:Huaqiao Ma, Mina Luo, Shijun Shao, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2008 Volume 1192(Issue 1) pp:180-186
Publication Date(Web):23 May 2008
DOI:10.1016/j.chroma.2008.03.050
The migration behavior of three calix[4]pyrroles (C4Ps) in acetonitrile (ACN) and in the mixtures of ACN/ethanol (EtOH) (95:5; v/v)with tetraalkylammonium chloride as background electrolyte (BGE) was studied. Electroosmotic flow (EOF) mobilities and absolute mobilities in ACN and mixture of ACN/EtOH (95:5; v/v) were investigated. A decrease of EOF mobilities in EtOH/ACN was observed compared with that of in pure ACN. Variation of the C4Ps effective mobilities as a function of the square root of concentration of tetraakylammonium chloride salts such as tetramethylammonium chloride (Me4NCl), tetraethylammonium chloride (Et4NCl) and tetrabutylammonium chloride (Bu4NCl) in both solvents was plotted, and straight lines were exhibited when Bu4NCl was used as BGE. Absolute mobilities of C4Ps were obtained by extrapolation from the mentioned plots. It was found that the absolute mobilities of C4Ps is independent of the nature of BGE and the values are: meso-octamethylcalix[4]pyrrole (OMCP) > meso-tetracyclopentylcalix[4]pyrrole (TPCP) > meso-tetracyclohexylcalix[4]pyrrole (THCP). The ion-pairing constants follow the order under given solvent: Me4N+ > Et4N+ > Bu4N+, and ion-pairing constant of C4P follows the order: THCP > TPCP > OMCP. As though, ion-pairing association is intensified by steric hindrance.
Co-reporter:Xiaojing Liang, Quansheng Chen, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2008 Volume 1182(Issue 2) pp:197-204
Publication Date(Web):29 February 2008
DOI:10.1016/j.chroma.2008.01.013
A new stationary phase N-methylimidazolium functionalized ZrO2/SiO2-4 (Zr/SilprMim) has been prepared. The chromatographic property of this stationary phase is investigated by ion chromatography (IC) with inorganic and organic anions, and normal phase HPLC with basic compounds and hydroxybenzenes. The effects of pH and the strength of Lewis base of eluent on separation of anions are studied. This new stationary phase is also compared with a N-methylimidazolium functionalized SiO2 stationary phase (SilprMim). The results show that this new stationary phase can be used in analysis of inorganic anions with great prospects. At the same time, successful separations of some organic anions can be obtained by using phosphate buffer solution as mobile phase. This new stationary phase also has a distinct advantage in the separation of basic compounds in normal phase. But due to the presence of Lewis acid sites on the surface of ZrO2/SiO2-4, Lewis bases such as hydroxybenzenes adsorb very strongly on this new stationary phase, and Lewis acid sites can be masked or modified by the eluent that contain Lewis base groups.
Co-reporter:Huaqiao Ma, Mina Luo, Shijun Shao, Xia Liu, Shengxiang Jiang
Journal of Chromatography A 2008 Volume 1188(Issue 1) pp:57-60
Publication Date(Web):18 April 2008
DOI:10.1016/j.chroma.2007.09.087
A study on the migration behavior of four neutral macrocyclic compounds calix[4]pyrroles (C4Ps) by nonaqueous capillary electrophoresis (NACE) with tetrabutylammonium halide salts as background electrolyte (BGE) is described. Systematic studies were carried out with different BGE in acetonitrile (ACN) to elucidate the involved phenomena. The effect of BGE concentration on analytes effective mobilities μeff,i was studied. Rough values of analytes absolute mobilities μ∞,i were obtained by extrapolation of effective mobilities to zero ionic strength of BGE. Stokes radius of C4Ps in the form of C4PF− and C4PCl− was calculated. The complex constants of C4Ps with F− anion and Cl− anion and ion-pair association constants of each C4PF− and C4PCl− with tetrabutylammonium cations was evaluated and confronted. Hydrogen bonding effect is prerequisite in the separation; meanwhile ion-pair association which is intensified by steric hindrance effect plays an important role.
Co-reporter:Hao Tang, Guangtao Min, Bin Ge, Yumin Li, Xia Liu, Shengxiang Jiang
Journal of Ethnopharmacology (22 May 2008) Volume 117(Issue 3) pp:420-426
Publication Date(Web):22 May 2008
DOI:10.1016/j.jep.2008.02.020
Aim of the studyChi-Zhi-Huang decoction (PGR) is one of the traditional Chinese medicine (TCM) preparations with unique effect on withdrawing jaundice and has been used to treat icteric patients in China for many years. In this research, we aim at to evaluate the potential activity of PGR in restoring hepatic drug metabolism in a damaged liver.Materials and methodsA cocktail approach with caffeine (10 mg/kg), dapsone (10 mg/kg) and chlorzoxazone (20 mg/kg) respectively as probe drug of cytochrome P450 (CYP) isoform of CYP 1A2, 3A4 and 2E1 was used to evaluate its possible effects on Phase I oxidative metabolism. Pretreated with three dosages of PGR water extract (0.75, 1.5 and 3 g/kg, po) for 5 days, male Wistar rats (220–240 g) were intoxicated by phenylisothiocyanate (PITC, 100 mg/kg, po) 24 h before probes intravenous injection. The pharmacokinetics of the probes in the blood was determined simultaneously by HPLC, and their non-compartmental parameters were used to evaluate the metabolic difference among the groups. Moreover, the levels of liver enzymes (ALT, AST, ALP) and bilirubins were also measured for insight of liver function.ResultsThe findings in this study suggest that PGR induces CYP 3A4, does not have much effect on CYP 2E1, and inhibits CYP 1A2 at high dosage.ConclusionThe current pharmacokinetic approach allowed the protective effects of PGR on oxidative drug metabolism in damaged liver to be systemically examined and will certainly help in the explanation of synergistic effect of the composites formula.
