bluuebunny/crossref_metadata_2025_split huggingface dataset:
Capillary electrochromatographic separation of ionizable compounds with a molecular imprinted monolithic cationic exchange column
Authors: Yan Weiying , Gao Ruyu , Zhang Zhichao , Wang Qinsun , Jiang Chun Vernon , Yan Chao 
Published: May 2003

AbstractA polymer‐based monolithic capillary column imprinted with 4‐aminopyridine (4‐AP) was prepared by a thermally‐initiated polymerization process; and its performance as a capillary electrochromatographic medium was evaluated in separating 4‐AP and 2‐AP isomers. The effects of experimental parameters, such as pH value and ionic strength of the buffer, the acetonitrile content in the mobile phase, and the applied voltage, on the resolution of these isomers had been carefully investigated. It was found that in the retention process there were interplays of multiple mechanisms of ion‐exchange, molecular imprinting, and electrophoresis. These mechanisms allowed more sophisticated control of experimental parameters in the separation of ionizable compounds.
Decoding of complex isothermal chromatograms: Application to chromatograms recovered from space missions
Authors: Pietrogrande Maria Chiara , Tellini Ilaria , Felinger Attila , Dondi Francesco , Szopa Cyril , Sternberg Robert , Vidal‐Madjar Claire 
Published: May 2003

AbstractIn gas chromatographic isothermal separations of multicomponent mixtures, i.e., mixtures where the number of components is high and unknown, the efficiency is low and not enough to allow a complete separation with a consequent severe peak overlapping in the chromatogram. The consequence is a significant loss in analytical information content. Therefore it is practically mandatory to use a chemometric procedure to decode the complex chromatogram, i. e. to deconvolve the overlapping signal to extract from it information on the mixture and the separation system. Isothermal separations are not very popular, due to their low efficiency, but they are very common in in situ analyses during space missions, as a consequence of flight constraints on instrumentation complexity and power (energy saving). In this work a chemometric approach based on Fourier analysis is applied to chromatograms obtained under isothermal or low temperature programming conditions. These conditions simulate those employed in space missions. The procedure has been applied to standard mixtures containing compounds representative of the planetary atmospheres that will be investigated in the near future: in particular, those related to Titan's atmosphere (Cassini‐Huygens mission) and a cometary nucleus (Rosetta mission), i. e., hydrocarbons and oxygenated compounds with carbon atom numbers ranging from 2 to 8. The original approach, developed for constant peak width, is extended to variable peak width, in particular to the case of peak width linearly increasing with retention time, representing isothermal separations. The proposed approach is able to characterise complex isothermal chromatograms in terms of number of components present in the mixture and of separation efficiency: such results are useful in interpreting data recovered from space missions and for optimising analysis conditions compatible with flight constraints.
Peak amplitude and resolution in comprehensive gas chromatography using valve modulation
Authors: Hamilton Jacqueline F. , Lewis Alastair C. , Bartle Keith D. 
Published: May 2003

AbstractComprehensive two‐dimensional gas chromatography (GC×GC) allows major increases in peak capacity in comparison with separations on a single column. Interfacing the two columns in GC×GC has most often been achieved by thermal modulation. However, analyte transfer by valve modulation, in which fractions from the first column are introduced into the second column by means of a multi‐port valve, is also possible. In this paper we develop a previous model of peak amplitude enhancement to compare the sensitivity and resulting resolution possible in GC×GC with thermal and valve modulation. While the peak amplitude resulting from valve modulation is inevitably much less than in thermal modulation, there is still an enhancement in comparison to single column GC. Resolution (R) in GC×GC with the two modulation methods has also been compared and is predicted to be generally improved for the valve modulation of partially resolved (R = 1) narrow peaks from the first dimension column. A comparison of peak amplitude enhancement and retained resolution using thermal and valve modulation methods is made using the example of GC×GC analysis of gasoline vapour.
Discrimination of combustion fuel sources using gas chromatography‐planar field asymmetric‐waveform ion mobility spectrometry
Authors: Eiceman Gary A. , Tarassov Alexander , Funk Paul A. , Hughs S. Edgar , Nazarov Erkinjon G. , Miller Raanan A. 
Published: May 2003

AbstractSmoke plumes from cotton, paper, grass, and cigarettes and emissions from a gasoline engine were sampled using solid‐phase microextraction (SPME) and samples were analyzed for volatile organic compounds (VOC) using gas chromatography‐mass spectrometry (GC‐MS). Chemical compositions were sufficiently distinct to allow source identification. Unfortunately, advanced smoke detectors based on GC‐MS would be too slow and expensive for most applications. Direct sampling of smoke by atmospheric pressure chemical ionization‐mass spectrometry produced a complex response, demonstrating that VOC in smoke were suitable for gas phase chemical ionization. The complexity also indicated the necessity of chromatographic prefractionation. Planar Field Asymmetric‐waveform Ion Mobility Spectrometry (PFAIMS) as a capillary GC detector generated chemical information orthogonal to GC retention times. The combination of SPME preconcentration and the additional information provided by the PFAIMS detector yielded unique patterns from smoke from each fuel. Reconstructed ion chromatograms extracted from the PFAIMS scans indicated sufficient resolution of chemical constituents could be completed in less than five minutes with little loss of analytical information. These first measurements suggest that a GC‐PFAIMS instrument operating at ambient pressure in air might result in a compact and convenient fuel specific smoke alarm at a reasonable cost.
Automated rotary valve injection for polybrominated diphenyl ethers in gas chromatography
Authors: Björklund Jonas , Tollbäck Petter , Dyremark Eva , Östman Conny 
Published: May 2003

AbstractA simple, automated rotary valve injector for gas chromatography was constructed and evaluated for injection of polybrominated diphenyl ethers with molecular weights ranging from 485 to 949 Dalton. These congeners, particularly those with nine and ten bromine substituents, constitute a severe problem when a split/splitless vaporizing injector is used for gas chromatographic determination of polybrominated diphenyl ethers. Volumes up to 50 μL were injected without the need for a solvent vapor exit. Discrimination of the high molecular weight brominated diphenyl ether congeners with seven to ten bromine substituents is strongly reduced. The injector exhibits both high reproducibility and low carry‐over effects. Average relative standard deviation of the absolute peak area was less than 3.5% and for the carryover it was less than 0.4%. An important observation is that the electron capture detector response factors remained constant independent of injection volume, allowing large volume injection to decrease sample concentration detection limits, which is an important feature regarding determination of high molecular weight polybrominated diphenyl ethers. A further advantage is that the rotary valve large volume injector facilitates on‐line coupling of various clean‐up systems to the gas chromatograph.
Supported‐liquid membrane extraction as a selective sample preparation technique for monitoring uranium in complex matrix samples
Authors: Chimuka Luke , Cukrowska Ewa , Soko Lorraine , Naicker Koovila 
Published: May 2003

AbstractA supported liquid membrane (SLM) extraction method is described for selective extraction of uranyl cation using tri‐n‐butyl phosphate (TBP) as an extractant and kerosene as a diluent. Sodium sulphate was used as the acceptor phase as well as the electrolyte solution in the final determination using adsorptive stripping voltammetry (AdSV) on a hanging mercury drop microelectrode (HMDE). The developed and optimised method was used for monitoring of uranium as a uranyl cation in environmental samples with complex matrices. Important parameters controlling the extraction process, viz. the pH of the donor and the acceptor phase and the concentration of the acceptor phase, were investigated. The specificity of sodium sulphate‐uranyl complex formation in the acceptor determined the selectivity of the extraction process. The original sample input into the membrane showed high concentrations of other metals to be present, yet the concentration of these metals in the acceptor solution of the membrane was very low. The slow mass transfer of the extraction process was also investigated. The stripping of uranyl cation into the acceptor solution was found to be the limiting factor. The detection limit of the method was around 0.5 μg L–1 after extraction of a 30 mL sample volume for 60 minutes.
Improving injection precision in packed‐column supercritical fluid chromatography
Authors: Coym Jason W. , Chester Thomas L. 
Published: May 2003

AbstractIt is often observed that peak area precision in packed column supercritical fluid chromatography (pSFC) is rather poor when compared to values obtained in HPLC. Since the valves used for sample introduction in both techniques are identical, it is reasonable to expect that injection precision should be similar, especially when full‐loop injections are performed. We found that in pSFC the evaporation of the mobile phase from the loop, when decompressed just prior to sample loading, contributes strongly to injection problems. However, these problems can be avoided if the injection valve, sample loop, and associated port tubes are entirely filled with liquid before the sample solution is loaded into the sample loop. By being mindful of the sequence of events that occurs during a full‐loop injection, and by taking into account both the compressible nature and volatility of pSFC mobile phases and the geometry of the injection device, injection precision in pSFC can be comparable to that observed in HPLC.
Determination of biogenic amine neurotransmitters by RP‐HPLC/FL method on Chromolith RP18e stationary phase
Authors: Baranowska Irena , Zydron Miroslawa 
Published: May 2003

AbstractThe Chromolith RP‐18e stationary phase (Merck, Darmstadt, Germany) was tested for the separation of biogenic amine neurotransmitters and their derivatives. Citrate, acetate, and phosphate buffer solutions with methanol and acetonitrile as modifiers were used as the mobile phases. The tested column proved its high efficiency for the separation of the compounds of interest, resulting in short retention times and permitting working with low pressure. Three gradient systems were developed. The best results were obtained for acetate buffer solution with methanol as the modifier. The system was applied to the analysis of urine samples.
Immuno affinity purification combined with mass spectrometry detection for the monitoring of VEGF isoforms in patient tumor tissue
Authors: Landuyt Bart , Jansen Jaap , Wildiers Hans , Goethals Laurence , De Boeck Gert , Highley Martin , van Oosterom Allan T. , Tjaden Ubbo , Guetens Gunther , de Bruijn Ernst A. 
Published: May 2003

AbstractVascular endothelial growth factor (VEGF) is a key mediator of tumor growth and metastasis. At least 7 isoforms of the protein exist due to differential splicing, but little is known about the biological activities of these different isoforms. We purified VEGF from resected human bronchial carcinoma tissue and normal bronchus by immuno affinity chromatography (IAC) and immuno capture (IC) on a ProteinChip® Array, identifying the isoforms by MS. Both methods proved to be useful for the analysis of protein isoforms, which are present in situ in tumor tissue. Different expression patterns of VEGF were demonstrated in tumor tissue compared to healthy tissue. The possibility to analyse VEGF protein isoforms in situ creates new opportunities to study the regulation of angiogenesis in healthy and malignant tissues.
Modified headspace‐SPME‐GC device for sampling volatile compounds in acidic medium
Authors: Araújo W. A. , Lacerda C. A. , Cappelaro E. A. , Lanças Fernando M. 
Published: May 2003

AbstractMost of the existing analytical methods for determining dithiocarbamate pesticide residues utilize an acid decomposition step, which promotes the release of carbon disulfide from the pesticide molecule. After release, the CS2 is sampled by static headspace techniques using gas‐tight syringes and analyzed by gas chromatography with flame photometric detection (GC‐FPD). In our search for faster analytical methodologies for sampling of volatile compounds we have used solid phase microextraction (SPME). However, evaluation of the commercially available SPME system for the analysis of CS2 obtained by decomposing dithiocarbamates showed it to be unsuitable for analysis in an acidic environment. The present communication reports the development of an appropriate device for sampling volatile compounds in an acidic environment by static headspace‐SPME followed by GC‐FPD. On examining the limitations of using a standard metal needle in HS‐SPME sampling of analytes in acidic medium, a corrosion process was observed in both needle and fiber. A new double‐needle device which avoids such corrosion problems was developed and built. The successful application of this device to the analysis of mancozeb in water samples is described.
Development of cryogenic chromatography using thermoelectric modules for the separation of methyltin compounds
Authors: Jiemin Liu , Guibin Jiang , Jingfu Liu , Qunfang Zhou , Ziwei Yao 
Published: May 2003

AbstractA nonliquid cryogenic gas chromatograph using thermoelectric modules for the cryogenic separation of low boiling‐point compounds was developed. The new system included four thermoelectric modules, a U shape heat exchanger, a cold block, a temperature controller, and three aluminum sheets. The minimum operating temperature of the assembly was –10°C. This thermoelectric system was used to directly cool the capillary column, without any need for a traditional cryogen and had a small volume. The system was cost‐effective and convenient to operate. It was successfully applied to the separation of methyltin species.
Postcolumn derivatization in microcolumn liquid chromatography
Authors: Takeuchi Toyohide , Masuoka Shinichi , Jin Ji‐Ye 
Published: May 2003

AbstractA postcolumn derivatization system was assembled using a commercially available Nano Y Connector with low dead volume for microcolumn liquid chromatography. Smooth baselines were achieved when postcolumn reagent solution and mobile phase were supplied by one microfeeder equipped with two syringes. Amino acids and inorganic anions were visualized by the postcolumn reaction with tolerable extracolumn band broadening.
Anodic behaviour of WC‐Co type hardmetal
Authors: Bozzini B. , De Gaudenzi G. P. , Fanigliulo A. , Mele C. 
Published: May 2003

AbstractAn understanding of the anodic behaviour of WC‐Co type hardmetals is vital for the functional behaviour of this class of materials. The anodic oxidation of WC‐13Co grade hardmetal in 0.1 M H2SO4 was investigated. This study is based on electrochemical (linear sweep voltammetry, cyclic voltammetry, impedance spectroscopy), compositional (energy dispersive spectroscopy), structural (X‐ray diffraction) and morphological (scanning electron microscopy) investigations. The potential range in which the oxidation of the Co‐alloy takes place with respect to the nobler carbide phase was defined. Within this potential interval a passivating behaviour for the binder alloy was shown. The potential threshold for WC oxidation was identified by monitoring the inception of the electrochromic loop. The anodic attack gives rise to the formation of hydrous WO3. The attack morphology is characterised by the alteration of the grain shape with formation of jelly‐like microscopic and flaky macroscopic structures.
Corrosion of atomized Fe40Al based intermetallics in molten Na2SO4
Authors: Espinosa M. A. , Carbajal De la Torre G. , Porcayo‐Calderon J. , Martinez‐Villafañe A. , Chacon‐Nava J. G. , Casales M. , Gonzalez‐Rodriguez J. G. 
Published: May 2003

AbstractThe hot corrosion resistance of sprayed and atomized Fe‐40at.%Al, Fe40Al+0.1B and Fe40Al+0.1B+10Al2O3 intermetallic materials have been evaluated in molten Na2SO4 at 900 and 1000°C using polarization curves and polarization resistance measurements. The results are supported by electron microscopy and microchemical studies. The tests lasted 5 days. At 900°C the Fe40Al material had the lowest corrosion rate (0.03 mA/cm2), and the Fe40Al+0.1B+10Al2O3 exhibited the highest. At 1000°C, the Fe40Al+0.1B material, was the material that had the best corrosion resistance with less than 0.02 mA/cm2 in the first 50 hours, whereas the Fe40Al presented the worst corrosion resistance with 0.20 mA/cm2. The results are discussed in terms of the establishment of an Al2O3 layer that gives corrosion resistance to the materials and promotes an Al depletion in the FeAl matrix which allows the sulfides formation.
Influence of reinforcement grade and matrix composition on corrosion resistance of cast aluminium matrix composites (A3xx.x/SiCp) in a humid environment
Authors: Pardo A. , Merino M. C. , López M. D. , Viejo F. , Carboneras M. , Merino S. 
Published: May 2003

AbstractA study of the influence of the silicon carbide (SiCp) proportion and the matrix concentration of four aluminium metal matrix composites (A360/SiC/10p, A360/SiC/20p, A380/SiC/10p, A380/SiC/20p) exposed to high relative humid environment was carried out under simulation in a climatic chamber. The matrix of A360/SiC/xxp composites was virtually free of copper while the A380/SiC/xxp matrix contained 3.13‐3.45wt% Cu and 1.39‐1.44wt% Ni. The kinetics of the corrosion process was studied on the basis of gravimetric tests. The nature of corrosion products was analysed by Scanning Electron Microscopy (SEM) and Low Angle X‐Ray Diffraction (XRD) before and after accelerated testing to determine the influence of microstructural changes on corrosion behaviour during exposure to the corrosive environment. The corrosion damage to Al/SiCp composites was low at 80% Relative Humidity (RH) and increased with temperature, SiCp proportion, relative humidity and Cu matrix concentration. The main attack nucleation sites were the interface region between the matrix and the reinforcement particles. The corrosion process was influenced more by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement.
Electrochemical behaviour of an archaeological bronze alloy in various aqueous media: New method for understanding artifacts preservation
Authors: Souissi N. , Bousselmi L. , Khosrof S. , Triki E. 
Published: May 2003

AbstractThe aim of this work is to investigate the electrochemical behaviour of an archaeological bronze in several aqueous electrolytes (Na2SO4, NaCl, KOH, NaHCO3 and Na3PO4) at 0.01 M. The anodic polarization revealed the dissolution of the material independently from the corrosive medium, but the damaging action is stronger for sulfate and chloride where the pH was below 7. Electrochemical impedance spectroscopy permitted to establish a damage ranking based on the pH of the electrolytes: SO42– > Cl3– ≫ OH– > HCO3– > PO43–. Phosphate was tested successfully as inhibitor for archaeological bronzes against the corrosive action of sulfate and chloride.
Behavior of Ni‐base alloy 625 in methanol‐supercritical water systems
Authors: Boukis N. , Habicht W. , Franz G. , Dinjus E. 
Published: May 2003

AbstractMethanol reacts with water under supercritical conditions to form a hydrogen rich gas. This reforming reaction can be performed without the addition of a catalyst. Typical reaction conditions are 25 MPa pressure and 600°C temperature and short residence times. The tubular flow reactor used was made of the nickel base alloy 625. The reactor was operated continuously for more than 1000 hours without problems. The feed concentration was 5 weight‐% methanol. The major component of the product gas was hydrogen (up to more than 70 vol‐%). Methanol conversion was higher than 99% and the liquid effluent was clear and free of soot. After exposure, the reactor has been sectioned and each section has been analyzed. No major corrosion phenomena were observed. Severe ductility loss of the material could be measured in the higher temperature section of the reactor.
Material selection of safety‐relevant components in indoor swimming pools
Authors: Faller M. , Richner P. 
Published: May 2003

AbstractSuspended ceilings in indoor swimming pools are safety‐relevant components. As was demonstrated by the collapses of the ceiling of the Uster (CH) indoor swimming pool (1985) and again at Steenwijk (NL, 2001) greater attention has to be paid to selecting suitable materials and inspecting the state of such components. Our findings according to corrosion of metal fastening components of more than 150 indoor swimming pools in Switzerland are reported. The corrosion behaviour of stainless steels and galvanized steels are compared and discussed including newer results from the literature.
Critical Conformational Change of Poly(oxypropylene)diamines in Layered Aluminosilicate Confinement
Authors: Lin Jiang‐Jen , Chen I‐Jein , Chou Chih‐Cheng 
Published: May 2003

AbstractThe intercalation of aluminosilicate clays proceeds via a critical conformation change. Ion exchange of the poly(oxypropylene)diamine salts allows widening of the clay layers from 12 Å to 20 Å and then a sharp increase to 58 Å. The data indicate a critical conformation change of the intercalated amines, thus providing a new way for manipulating nanomaterials and control of polymer conformations in layered silicate confinement.Schematic illustration of POP‐amine self‐assembly in silicate confinements.magnified imageSchematic illustration of POP‐amine self‐assembly in silicate confinements.
Reactivity of Diamine Monomers in Non‐Equilibrium Copolycondensation Toward Aromatic Copolyamides
Authors: Du Zhuwei , Li Lei , Zhou Qixiang , Liu Deshan 
Published: May 2003

AbstractBased on the Hammett equation, a general method is established to relate the polycondensation monomer reactivity with both the monomer structural parameters and the properties of the solvent used for the non‐equilibrium ternary copolycondensation to give copolyamides. Linear plots of the logarithm of the monomer reactivity ratio, log r, versus structure parameter ΔpK could be represented by the equation log r = ρΔpK.Relationship between log r and ΔpK using THF as the solvent.magnified imageRelationship between log r and ΔpK using THF as the solvent.
Polymerization of Methyl Methacrylate with Ni(II) α‐Diimine/MAO and Fe(II) and Co(II) Pyridyl Bis(imine)/MAO
Authors: Kim Il , Hwang Jeong‐Mi , Lee Jin Kook , Ha Chang Sik , Woo Seong Ihl 
Published: May 2003

AbstractPolymerizations of methyl methacrylate with (α‐diimine)nickel(II)/methylaluminoxane (MAO) and (pyridyl bis(imine))iron(II) and (pyridyl bis(imine))cobalt(II)/MAO are reported. Effects of structural variation of the ligand on the activities of catalysts and polymer microstructure are described. The catalyst systems gave syndio‐rich poly(methyl methacrylate). The α‐diimine system showed much higher activity than the pyridyl bis(imine) systems under similar polymerization conditions.
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