bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐performance liquid chromatographic determination of memantine hydrochloride in rat plasma using sensitive fluorometric derivatization
Authors: Xie Mei‐Fen , Zhou Wei , Tong Xin‐Yi , Chen Yi‐Le , Cai Yi , Li Yan , Duan Geng‐Li 
Published: January 2011

AbstractIn this study, we investigated a simple, sensitive and reliable liquid chromatography‐fluorescence detection method for the determination of memantine hydrochloride in rat plasma which was based on derivatization with 9‐fluorenylmethyl chloroformate (FMOC‐Cl). For the first time, FMOC‐Cl was introduced into derivatization of memantine hydrochloride in rat plasma. The amino groups of memantine hydrochloride and amantadine hydrochloride (internal standard) were trapped with FMOC‐Cl to form memantine hydrochloride‐FMOC‐Cl and amantadine hydrochloride‐FMOC‐Cl compositions, which can be very compatible for LC‐FLD. Precipitation of plasma proteins by acetonitrile was followed by vortex mixing and centrifugation. Chromatographic separation was performed on a C18 column (DIAMONSIL 150×4.6 mm, id 5 μm) with a mobile phase consisting of acetonitrile and water at a flow rate of 1.0 mL/min. The retention times of memantine hydrochloride‐FMOC‐Cl and amantadine hydrochloride‐FMOC‐Cl compositions were 23.69 and 40.27 min, respectively. Optimal conditions for the derivatization of memantine hydrochloride were also described. The limit of quantification (LOQ) was 25 ng/mL for memantine hydrochloride in plasma, the linear range was 0.025–5.0 μg/mL in plasma with a correlation coefficient (r) of 0.9999. The relative standard deviations (RSDs) of intra‐day and inter‐day assays were 4.46–12.19 and 5.23–11.50%, respectively. The validated method was successfully applied to the determination of memantine hydrochloride in rat plasma samples.
Purification of compounds from Lignum Dalbergia Odorifera using two‐dimensional preparative chromatography with Click oligo (ethylene glycol) and C18 column
Authors: Feng Jiatao , Xiao Yuansheng , Guo Zhimou , Yu Danhua , Jin Yu , Liang Xinmiao 
Published: January 2011

AbstractPurification of compounds from traditional Chinese medicines (TCMs) is an important task for understanding the chemical composition of TCMs. However, it is difficult to obtain compounds with high enough purity for identification by NMR due to the complexity of TCMs in chemical composition. In this study, a two‐dimensional purification method based on a Click oligo (ethylene glycol) column and a C18 column was developed to realize an orthogonal separation in preparative level for purifying compounds efficiently. The first dimensional preparation was performed on a Click oligo (ethylene glycol) column to simplify the sample into the fractions with good separation repeatability. On the first dimension, 7.2 g sample was separated into 11 fractions with a recovery of 86% within 6 h. A C18 column was taken as the second dimension to realize the high‐performance separation and rapid preparation from the fractions collected from the first dimension. Eight compounds in fraction 6 and 2 compounds in fraction 8 were isolated and identified after optimizing the separation and collection parameters. This method is a high‐efficient and orthogonal preparation method to improve the separation of a complex sample and increase the purity of the compounds, which benefits from the application of novel materials in the preparation and purification.
Simultaneous quantification of diterpenoids in Premna integrifolia using a validated HPTLC method
Authors: Yadav Deepti , Tiwari Neerja , Gupta Madan M. 
Published: January 2011

AbstractA sensitive, selective and robust densitometric high‐performance thin layer chromatographic method was developed and validated for the determination of diterpenoids in the root bark of Premna integrifolia. Diterpenoids 1β,3α,8β‐trihydroxy‐pimara‐15‐ene (A), 6α,11,12,16‐tetrahydroxy‐7‐oxo‐abieta‐8,11,13‐triene (B) and 2α,19‐dihydroxy‐pimara‐7,15‐diene (C) were used as chemical markers for the standardization of P. integrifolia plant extracts. The separation was performed on silica gel 60F254 high‐performance thin layer chromatography plates using hexane/acetone/ethylacetate (60:20:20 v/v) as mobile phase. The quantitation of diterpenoids was carried out using densitometric reflection/absorption mode at 475 nm after post‐chromatographic derivatization using vanillin–sulfuric acid reagent. A precise and accurate quantification can be performed for compounds A, B and C in the linear working concentration range of 1–10 μg/spot with good correlations (r2=0.9985, 0.9996 and 0.9992, respectively). The method was validated for peak purity, precision, robustness, limit of detection (LOD) and quantitation (LOQ) etc., as per the International Conference on Harmonization (ICH) guidelines. Specificity of quantitation was confirmed using retention factor (Rf) and spectra correlation of markers in standard and sample tracks. The method reported here is simple and reproducible which may be applied for quantitative analysis of above diterpenoids in the root bark of P. integrifolia.
Quantification of flavonoid glycosides in an aqueous extract from the traditional Mongolian medicinal plant Dianthus versicolorFISCH.
Authors: Obmann Astrid , Zehl Martin , Purevsuren Sodnomtseren , Narantuya Samdan , Reznicek Gottfried , Kletter Christa , Glasl Sabine 
Published: January 2011

AbstractAn HPLC‐diode array detection (DAD) method was established in order to investigate dried aerial parts of Dianthus versicolor FISCH. (Caryophyllaceae), a plant used in traditional Mongolian medicine against liver impairment. Aqueous extracts were separated on an Aquasil® C18 column with a linear gradient of acetonitrile (ACN) and water (adjusted to pH 2.8 with formic acid) as the mobile phase. LC‐IT‐MS facilitated the assignment of 26 flavonoids, among them a series of rare C‐glycosylated as well as O‐glycosylated derivatives, which are assumed to be the active principles. Quantification was performed and validated using isovitexin‐7‐O‐glucoside (saponarin) as the external standard. The method showed good linear behaviour (r2 ≥0.9999) over the investigated concentration range (0.007–3.5 mg/mL). The good precision of the method allowed the successful qualitative and quantitative analysis of flavonoid‐glycosides in the aqueous extracts prepared from five different D. versicolor samples. Depending on the origin of the samples, the total flavonoid content was found to vary considerably from 0.41 to 3.30% in the aqueous extracts and from 0.07 to 0.57% in the crude drug. In addition, the relative composition of the various flavonoids was found to differ strongly. These results highlight the need for proper quality control for this herbal drug.
Solid‐phase extraction and ultra high‐performance liquid chromatography tandem mass spectrometry analysis of the gastrointestinal absorption of emodin in different digestive segments of rats
Authors: Kong Weijun , Xia Xinhua , Wang Jiabo , Zhou Canping , Fang Fang , Xing Xiaoyan , Jin Cheng , Zhao Yanling , Zang Qingce , Xiao Xiaohe 
Published: January 2011

AbstractA rapid, simple and sensitive ultra high‐performance liquid chromatography (UHPLC‐MS/MS) method was established for determining the absorption amount of emodin in the five digestive segments of rat. Plasma samples were pre‐purified by solid‐phase extraction (SPE) with Oasis MAX cartridge. Separation of emodin and 1,8‐dihydroxyanthraquinone (internal standard) was performed on an Acquity BEH UHPLC C18 column (100 mm×2.1 mm, 1.7 μm) with gradient elution of methanol and 0.1% formic acid aqueous solution. The LC/MS system was operated under multiple reaction monitoring mode using electrospray ionization (ESI) in negative ion mode. The results showed that this established method was valid and sensitive for emodin within 0.04–16.4 μg/mL, with low limits of detection and quantification of 0.6 ng/mL and 2.4 ng/mL, respectively and upper limit of quantification of 220.0 ng/mL. The intra‐ and interday variations were below 4.9% of RSD. The extraction recoveries were 98.9–106.1% with RSD of 1.9–3.2%. The plasma concentration‐time relationship showed that the absorption of emodin in stomach was faster than in intestine segments. The sequence of absorption amount was: ileum>jejunum>colon≈duodenum>stomach. Most of emodin was absorbed in ileum, and the absorption amount was increased with prolonged retention of drug form in intestine, especially in ileum and jejunum. The developed UHPLC‐ESI‐MS/MS method was appropriate for determining the in vivo absorption of emodin in other herbal medicines or preparations containing this compound.
Grafting Polymer Loops onto Functionalized Nanotubes: Monitoring Grafting and Loop Formation
Authors: Ashcraft Earl , Ji Haining , Mays Jimmy , Dadmun Mark 
Published: January 2011

AbstractPolystyrene functionalized at both ends (telechelic polymer) with epoxide groups (epoxy–PS–epoxy) was reacted with carboxylated multiwall carbon nanotubes (COOHMWNT) in solution in order to graft polymer chains at both ends onto the MWNT surface, forming loops. FT‐IR spectroscopy was employed to monitor the formation of aromatic esters and to quantify the amount of telechelic grafted to the nanotube surface as a function of reaction time. When the samples were further annealed in the melt, an increase in the aromatic ester peak was observed, indicating that the unreacted chain ends further grafted to MWNT surfaces to form loops. By reacting the grafted nanotube samples further with monocarboxy terminated poly(4‐methylstyrene) (COOHP4MS), the amount of epoxy–PS–epoxy that had only reacted at one end was determined. Reaction rate analysis indicates that that the grafting of epoxy–PS–epoxy to the nanotube surface is reaction controlled, as the FT‐IR spectroscopy signal grows as a function of approximately t0.3. These studies exemplify how FT‐IR spectroscopy can be used as a novel technique to quantify the amount of grafted polymer, grafting rate, and percent of difunctional polymers that form loops, and provide a method to create loop covered nanoparticles. magnified image
Visualization of Thermo‐Oxidative Degradation of Polyolefins in Solution Using HT‐SEC and HT‐AF4‐MALS
Authors: Otte Tino , Pasch Harald , Brüll Robert , Macko Tibor 
Published: January 2011

AbstractThe molar mass distributions of high‐molar‐mass PE and PP were characterized using HT‐AF4 and HT‐SEC in combination with IR and MALS detection. Calculated molar mass distributions, average molar masses and radii of gyration were compared. It was found that HT‐AF4 can detect the real extent of thermo‐oxidative degradation during dissolution. HT‐SEC is affected by shear and thermo‐oxidative degradation while in HT‐AF4 no shear stress exists. As a consequence, the molar mass averages obtained from HT‐SEC are pronouncedly lower as obtained from HT‐AF4. In addition, branched polyolefins cannot be correctly characterized by SEC‐MALS due to abnormal co‐elution effects. HT‐AF4 is therefore the method of choice for studying the thermo‐oxidative degradation of macromolecules with high molar masses. magnified image
Silver Nanoparticles in Blends of Polyethylene and a Superabsorbent Polymer: Morphology and Silver Ion Release
Authors: Stará Hana , Starý Zdeněk , Münstedt Helmut 
Published: January 2011

AbstractAntimicrobial properties of polymer materials are required in many applications. The polyethylene/superabsorbent polymer (PE/SAP) blends containing silver nanoparticles were successfully prepared via thermal reduction during melt mixing. It was found that in situ formed silver nanoparticles are preferentially located at the interface between PE matrix and SAP particles. The expectation was that the low water uptake of the PE will be enhanced by blending with a SAP and thus the silver ion release from the material will increase. Surprisingly, the silver ion release was markedly suppressed by the addition of SAP. This finding is explained by the preferential sorption of silver ions by the SAP particles. magnified image
Poly(propylene)/Carbon Nanofiber Nanocomposites: Ex Situ Solvent‐Assisted Preparation and Analysis of Electrical and Electronic Properties
Authors: Chen Xuelong , Wei Suying , Yadav Atarsingh , Patil Rahul , Zhu Jiahua , Ximenes Rey , Sun Luyi , Guo Zhanhu 
Published: January 2011

AbstractCNF‐reinforced PP nanocomposites were fabricated from CNFs dispersed in a boiling PP/xylene solution. Their thermal properties were characterized by TGA and DSC and shown to exhibit improved thermal stability and higher crystallinity. They were further processed into thin films by compression molding. The electrical conductivity and dielectric property of the PP/CNF nanocomposite thin films were studied. Both electric conductivity and real permittivity increased with increasing fiber loading. Electrical conductivity percolation is observed between 3.0 and 5.0 wt.‐% fiber loading. The rheological behavior of the nanocomposite melts were also investigated. It was found that a small fiber concentration affects the modulus and viscosity of PP melt significantly. magnified image
Thermoresponsive Block Copolymer–Protein Conjugates Prepared by Grafting‐from via RAFT Polymerization
Authors: Li Ming , Li Hongmei , De Priyadarsi , Sumerlin Brent S. 
Published: January 2011

AbstractWell‐defined “smart” block copolymer–protein conjugates were prepared by two consecutive “grafting‐from” reactions via reversible addition–fragmentation chain transfer (RAFT) polymerization. The initiating portion (R‐group) of the RAFT agent was anchored to a model protein such that the thiocarbonylthio moiety was readily accessible for chain transfer with propagating chains in solution. Well‐defined polymer‐protein conjugates of poly(N‐isopropylacrylamide) (PNIPAM) and bovine serum albumin (BSA) were prepared at room temperature in aqueous media. The retained trithiocarbonate moiety on the free end group of the immobilized polymer allowed the homopolymer conjugate to be extended by polymerization of N,N‐dimethylacrylamide. Polyacrylamide gel electrophoresis, size exclusion chromatography, and NMR spectroscopy confirmed the synthesis of the various conjugates and revealed that the polymerizations were well controlled. As expected, the resulting block copolymer–protein conjugates demonstrated thermoresponsive behavior due to the temperature‐sensitivity of the PNIPAM block, as evidenced by turbidity measurements and dynamic light scattering analysis. magnified image
Cyclodextrin Supramacromolecules: Unexpected Formation in Aqueous Phase under Ambient Conditions
Authors: Rao J. P. , Geckeler Kurt E. 
Published: January 2011

AbstractThe unexpected formation of supramacromolecules of β‐cyclodextrin in aqueous solution under ambient conditions is reported in this article. The shape and size of the supramacromolecules could be controlled by varying the stirring time and the concentration. The supramolecular interactions of the supramacromolecules were confirmed by 1H NMR spectroscopy. Additionally, visual evidence of the supramacromolecules was provided by transmission and scanning electron microscopy. The thermal behavior of the supramacromolecules was examined by thermogravimetric analysis. The molecular mass determination by gel permeation chromatography showed that the supramacromolecules had a high molar mass. magnified image
A Novel Low Solvent Method for Grafting Polyaniline to Silylated Silica
Authors: Wheelwright Walt V.K. , Ray Sudip , Easteal Allan J. 
Published: January 2011

AbstractSummary: Silica gel, an important inorganic polymer with many applications, was silylated with 3‐(phenylaminopropyl)trimethoxysilane (PAPTMOS) by means of a novel “low solvent” method, whereby the silane was dissolved in a small amount of methanol, mixed with silica and reaction carried out in a heated vacuum oven. Polyaniline (PANI) was grafted to the silylated silica by in situ polymerization of aniline, then dedoped with aqueous ammonia. Physically adsorbed PANI was removed from the modified silica by washing with tetrahydrofuran (THF) and N‐methyl‐2‐pyrrolidone (NMP). The silylated, PANI‐modified silica had electrical conductivity 1.2 × 10−3 S cm−1 after being re‐doped with methanesulfonic acid. FTIR, elemental analysis, X‐ray photoelectron spectroscopy, solid‐state 13C and 29Si NMR and morphological studies by SEM confirmed successful formation of the SiO2‐polyaniline hybrid material.
Effect of two Kinds of Imidazolium Ionic Liquids on the Microemulsion Polymerization of Methyl methylacrylate
Authors: Lu Jingjing , Ding Yunsheng , Yu Yun , Wu Shuying , Feng Wanggao 
Published: January 2011

AbstractSummary: In this paper, the microemulsion polymerization of methyl methylacrylate (MMA) was carried out with single and gemini ionic liquids as emulsifier including 1‐N‐tetradecyl‐3‐methylimidazolium bromide (C14MIM · Br) and 1, 4‐Bis (3‐tetradecylimidazolium‐1‐yl) butane bromide (C14MIM‐4‐C14MIM · 2Br) respectively, and they were all have typical microemulsion polymerization characters of MMA, but the process of polymerization directly depends on the structure of the imidazolium ionic liquids. The structure and concentration of ionic liquids have effects on the resulted latex particle sizes of PMMA, and much smaller size latexes of PMMA could be gotten with C14MIM · Br as emulsifier than C14MIM‐4‐C14MIM · 2Br in polymerization. On the other hand, the structure of emulsifier has the effects on the molecular weight (MW) and molecular weight distribution (MWD) of PMMA, so the resulting PMMA prepared from microemulsion polymerization with C14MIM · Br as emulsifier has higher MW but narrower MWD than that of PMMA with the same dosage of C14MIM‐4‐C14MIM · 2Br as emulsifier.
Preparation and Barrier Properties of Chitosan‐Layered Silicate Nanocomposite Films
Authors: Oguzlu Hale , Tihminlioglu Funda 
Published: January 2011

AbstractSummary: In this study, chitosan nanocomposite films were prepared using a solvent‐casting method by incorporation of an organically modified montmorillonite (Cloisite 10A). The effect of filler concentration on the water vapor permeability, oxygen permeability, mechanical and thermal properties of the composite films was evaluated. The structure of nanocomposites and the state of intercalation of the clay were characterized by XRD. The water vapor permeability of pure chitosan films was measured as a function of relative humidity (RH). It was found that the permeability value increased with an increase in RH. The water vapor and gas permeability values of the composite films decreased significantly with increasing filler concentration. Permeation data was fitted to various phenomenological models predicting the permeability of polymer systems filled with nanoclays as a function of clay concentration and aspect ratio of nanoplatelets. According to the XRD results, an increase in basal spacing was obtained with respect to pure clay for chitosan/clay nanocomposites. This demonstrated the formation of intercalated structure of clay in the polymer matrix. Tensile strength and elongation at break of the composites increased significantly with the addition of clay, however the thermal and color properties of the films were not much affected by the intercalation of clay into polymer matrix.
Preparation and Characterization of In‐Situ Polymerized Nanocomposites Based on Polyaniline in Presence of MWCNTs
Authors: Moniruzzaman Md. , Das C. K. 
Published: January 2011

AbstractSummary: Polyaniline (PANI) composites were prepared with both unmodified and amine modified MWCNTs with and without BaTiO3 through in‐situ oxidative polymerization. Uniform coating of PANI on the MWCNTs and BaTiO3 surfaces was found which was evident from the Field Emission Scanning Electron Microscopic (FESEM) and High Resolution Transmission Electron Microscopic (HRTEM) images. The structure of pure and amine modified MWCNTs was identified by Fourier Transform Infrared Spectroscopy (FTIR). The thermal stability of the amine modified composite with BaTiO3 is higher than that of the unmodified composite because of the better affinity between modified MWCNTs and polymer matrix and due to the higher stability of barium titanate itself. The capacitance of amine modified MWCNTs and BaTiO3 composites was less than that of the pure MWCNTs composites but the thermal stability increased in amine modified MWCNTs and BaTiO3 composites with respect to the pure MWCNTs composites. The maximum capacitance and energy density values were found in MWCNT/PANI composites which were equal to 523.20 F/g and 142.83 Wh/kg respectively at a scan rate of 10mv/s. Maximum power density was found to be 5147.70 W/kg in the same composite at a scan rate of 200 mv/s.
Implementation of Specific Bioconjugation in Polystyrene‐block‐poly(tert‐butyl acrylate)‐Based Bio‐Interfaces
Authors: Wasse1 Ekram , Ghassemi Sina , Schönherr Holger 
Published: January 2011

AbstractSummary: Here we report on the expansion of a previously introduced biointerface platform based on thin spin‐coated films of polystyrene‐block‐poly(tert‐butyl acrylate) (PS‐b‐PtBA). Following the selective deprotection of the tert‐butyl‐ester groups in the PtBA skin layer by hydrolysis under acidic conditions, the activation with N‐hydroxysuccinimide and the subsequent derivatization with α,ω‐biotin‐amine end‐functionalized poly(ethylene glycol) (PEG), strepavidin was immobilized as anchor layer for specific immobilization of biotin‐tagged molecules. Based on contact angle, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and confocal fluorescence microscopy data it was shown that the polymer films were efficiently modified. The complexation of a biotin‐tagged dye, as well as the non‐specific adsorption of proteins was determined by confocal fluorescence microscopy measurements. The surface coverage of the immobilized dye as a function of dye concentration in solution was found to be consistent with a high affinity‐type adsorption isotherm, while the protein resistant properties were found to be similar to non‐biotinylated PEG. The scope of micro‐ and nanostructured PS‐b‐PtBA biointerfaces is thereby considerably expanded to encompass the specific immobilization of biotin‐tagged biomolecules.
Characterization of Ethylene methyl methacrylate and Ethylene butylacrylate Copolymers with Interactive Liquid Chromatography
Authors: Chitta Rajesh , Brüll Robert , Macko Tibor , Monteil Vincent , Boisson Christophe , Grau Etienne , Leblanc Alexandra 
Published: January 2011

AbstractSummary: Copolymers of ethylene with methyl methacrylate (EMMA) and butyl acrylate (EBA), which are of different average chemical composition and block lengths according to NMR analysis, were analyzed by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), Crystallization Analysis Fractionation (CRYSTAF), and high performance liquid chromatography at high temperature (HT‐HPLC). With CRYSTAF and DSC crystallizing fractions were detected only in some samples. HT‐HPLC fractionated all the samples irrespective of their crystallinity. Homopolymers, PMMA and PE were also found in the copolymer samples of EMMA. EMMA and EBA were separated in HPLC according to the content of polar comonomer. A linear correlation between the MMA content and elution volume could not be established due to the presence of homopolymers as admixtures. In such a case the average chemical composition obtained by NMR does not correspond to the real chemical composition of the copolymers. Unlike EMMA the EBA samples eluted in single peaks, which was used for evaluation of their chemical composition distribution. The comparison of results obtained by fractionation via CRYSTAF and HT‐HPLC clearly demonstrates the advantages of the chromatographic approach to study the chemical heterogeneity of olefin based copolymers.