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991.
Cestari AR Vieira EF Dos Santos AG Mota JA de Almeida VP 《Journal of colloid and interface science》2004,280(2):380-386
In this work, chitosan beads were synthesized in acidic medium and cross-linked in 1% glutaraldehyde solution. The characterization of the materials using TG/DTG, XRD, and BET surface areas showed that the beads did not modify their characteristics after the cross-linking reaction. The cross-linked beads were utilized as adsorbents for the removal of the yellow-, blue-, and red-anionic reactive dyes from aqueous solutions at pH 2.0. Adsorption of the yellow-dye increased from 25 to 50 degrees C. However, adsorption of the blue-dye decreased from 25 to 50 degrees C. Interestingly, the adsorption of the red-dye decreased from 25 to 35 degrees C and increased from 45 to 50 degrees C. The kinetic data were evaluated using an Avrami kinetic model, where the parameter n was related to the determination of changes in the adsorption mechanisms. Adsorption data of the dyes in relation to the contact time, the chemical structures of the dyes, and temperature were presented and were discussed. 相似文献
992.
Summary An absorption method for the collection of acid and condensable volcanic gases is described. A Cd(OH)2 suspension allows the simultaneous sampling of sulfide and sulfur dioxide. A complete scheme for chemical analysis of H2O, CO2, H2S, SO2, HCl and HF is presented.The method is relatively simple and accurate and requires only simple equipment. Moreover, separate samples of the condensable part of the volcanic gas may be used for analysis of trace elements.
Probenahme und Analyse vulkanischer Gase
Zusammenfassung Eine Absorptionsmethode zur Probenahme saurer und kondensierbarer Vulkangase wurde beschrieben. Eine Cd(OH)2-Suspension ermöglicht die gleichzeitige Probenahme von H2S und SO2. Ein Analysenschema für die chemische Analyse von H2O, CO2, H2S, SO2, HCl und HF wurde angegeben. Das Verfahren ist relativ einfach und genau; es erfordert nur eine einfache Ausrüstung. Proben des kondensierbaren Anteils der Gase dienen zur Bestimmung der Spurenanteile.相似文献
993.
The organic nanoparticles of a blue-light-emitting molecule, 1,3-diphenyl-5-(9-anthryl)-2-pyrazuline, were prepared by reprecipitation method using acetonitrile as the solvent for the molecular precursor. Three morphologies, spherical, doughnut-shaped and cubic, could be observed on the silicon substrate forthe nanoparfides by the volume-controlled addition of acetonitrile. The evolution of particle morphology as a function of acetonitrile addition was attributed to the variation of the growth habits of the particles in the different environment. The nanoparticles exhibit the novel photoluminescence spectra as compared to those of monomer and the bulk crystals. 相似文献
994.
Stribeck N 《Analytical and bioanalytical chemistry》2003,376(5):608-617
The prospects of a modern analysis of nanostructure evolution during the processing of polymer materials by means of scattering from synchrotron radiation are demonstrated in examples. The beam sources have gained stability, shortages are located in beamline setups and in method development for the quantitative analysis of voluminous data sets.By using the proposed multidimensional chord distribution function (CDF) analysis method, nanostructure information from small-angle X-ray scattering (SAXS) data are extracted and visualised. The method can be automated if the beamline setup is able to deliver a full data set with simple constraints. In this case even a simultaneous data evaluation is possible (while one pattern is accumulated, the previous one is analysed). The advantages of the method are demonstrated in a study of the straining of a thermoplastic elastomer. The possibilities of an automated analysis are demonstrated in an investigation of the crystallisation behaviour of high-pressure injection-moulded polyethylene (HPIM-PE). The achievable results of nanostructure analysis of polymer materials are discussed. It is shown that the time-resolved SAXS of polymer materials studied during a transformation and analysed by the CDF method is not just a powerful tool to investigate the relationship between structure and properties of materials; the information that can be gained concerning the processes that control nanostructure evolution is equally important. In the future the enlightenment of such relationships may help to tailor polymer materials with respect to their properties and, beyond that, to improve assessments concerning their aging. 相似文献
995.
Santoyo E Verma SP Sandoval F Aparicio A García R 《Journal of chromatography. A》2002,949(1-2):281-289
A suppressed ion chromatography (IC) technique has been evaluated as a chemical monitoring tool for detecting major anions (F-, Cl-, NO3- and SO4(2-)) of condensed steam in geothermal power plants. It is shown that the suppressed IC technique provides a suitable means for preventing possible damage to generating equipment in the geothermal industry. An electrical conductivity detector (0.1 microS sensitivity) with an anion-exchange column (IonPac AS4A-SC), a micro-membrane suppressor (AMMS II), and an isocratic high-pressure pump system were successfully used for detecting low concentrations of inorganic anions. Method detection limits for the anions of interest were <0.184 mg/L. Details of the IC methodology as well as some experimental results obtained during its application for the chemical monitoring of geothermal steam pipes are also described. 相似文献
996.
Marcos J Pascual JA de la Torre X Segura J 《Journal of mass spectrometry : JMS》2002,37(10):1059-1073
A fast and sensitive method for the comprehensive screening of anabolic agents and other banned doping substances using gas chromatography/tandem mass spectrometry (GC/MS/MS) with an external ionization ion trap mass spectrometer is presented. The method takes advantage of the resolving power of MS/MS to eliminate background interferences, thus speeding up the chromatographic analysis. For each compound, different fragmentation reactions were studied and their collision energies optimized to obtain the best sensitivity in terms of their signal-to-noise ratio (S/N). A dramatic reduction in overall analysis time was achieved compared with other common approaches. More than 50 substances could finally be monitored in less than 7.4 min with detection limits (S/N >3) lower than 0.5 ng ml(-1) for most of the compounds with special sensitivity requirements according to the International Olympic Committee (IOC). A validation procedure for qualitative analysis was performed. The selectivity of the method showed that no interfering peaks were observed at the retention time of the analytes. Good intermediate precision, below 25% for most of the compounds, and robustness were observed. The optimized method was successfully applied to analyse more than 100 real human urine samples with optimum sensitivity and specificity rates. 相似文献
997.
Martinez-López S Morales-Noé A Pastor-Garcia A Morales-Rubio A de la Guardia M 《Journal of AOAC International》2005,88(4):1247-1254
The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid-liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile-water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15 degrees C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluorene to 500 nm for indeno(1,2,3-cd)pyrene. Recovery for all the compounds studied varied from 75 to 111%, and limit of detection values from 0.05 ng/g for benzo(k)fluoranthene to 0.48 ng/g for indeno(1,2,3-cd)pyrene, corresponding to 0.09 ng/g benzo(a)pyrene. Results were compared with those obtained by liquid-liquid extraction followed by a cleanup on silica and a direct GPC treatment of oil samples diluted in dichloromethane, 2 other methodologies that are appropriate for quantifying PAHs in olive oils. However, the proposed method improves the determination limits, reduces the time of analysis, and provides a highly stable baseline for sample chromatograms. 相似文献
998.
999.
Summary Extraction distribution of microamounts of cesium in the water-HCl-nitrobenzene-dibenzo-18-crown-6(L)-hydrogen dicarbollylcobaltate
has been investigated. The equilibrium data have been explained assuming that the complexes HL+, CsL+and CsL2,+are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated
with water have been determined. 相似文献
1000.
M. Domínguez-Pérez J. Jiménez de Llano L. Segade C. Franjo O. Cabeza 《Journal of Thermal Analysis and Calorimetry》2005,79(2):289-293
Summary This paper reports excess molar enthalpies of the binary systems hexane+ethyl benzene, hexane+o-xylene, hexane+m-xylene and hexane+p-xylene at 298.15 K and atmospheric pressure, over the whole composition range. The data was measured directly using a Calvet microcalorimeter. The excess magnitude was correlated to a Redlich-Kister type equation for each mixture. Also, we will discuss the results for the four mixtures studied here and by comparison with the same binary systems but containing propyl propanoate as first component. Finally, we will correlate our results with the Nitta-Chao and the three UNIFAC theoretical approximations. 相似文献