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64.
Aquino AJ Tunega D Haberhauer G Gerzabek MH Lischka H 《Journal of computational chemistry》2003,24(15):1853-1863
Hydrogen-bonded interactions between local defect structures on broken clay surfaces modeled as molecular clusters and the organic molecules acetic acid, acetate, and N-methylacetamide (NMA) have been investigated. Density functional theory and polarized basis sets have been used for the computation of optimized interaction complexes and formation energies. The activity of the defect structures has been characterized as physical or chemical in terms of the strength of the hydrogen bonds formed. Chemical defects lead to significantly enhanced interactions with stronger hydrogen bonds and larger elongation of OH bonds in comparison to the physical defects. The type of interaction with the defect structure significantly influences the planarity of the model peptide bond in NMA. Both cases, enhancement of the planarity by increase of the CN double bond character and strong deviations from planarity, are observed. 相似文献
65.
Richard St‐Louis Stephen de Mora milien Pelletier Bill Doidge Daniel Leclair Igor Mikaelian Daniel Martineau 《应用有机金属化学》2000,14(4):218-226
Butyltin (tributyltin TBT; dibutyltin DBT and monobutyltin MBT) speciation was measured in the liver of beluga whales from the St Lawrence Estuary and Hudson Strait (northern Quebec). Using GC–MS, liver samples were analysed from 21 beluga whales found dead, stranded along the shores of the St Lawrence during the period 1995–1998. In all cases, including a neonate specimen, the liver was contaminated with butyltin compounds with concentrations in the range 0.04–2.1 mg Sn kg−1 on a dry weight basis. Liver samples of five beluga whales from Hudson Strait obtained in the summer of 1998 were also analysed. For these animals, hepatic butyltin concentrations were consistently below the detection limit (<0.5 ng Sn g−1 for MBT and <0.2 ng Sn g−1 for DBT and TBT). Compared with published data on the contamination by TBT of the marine mammals of the St Lawrence in 1988, these contemporary results clearly indicate that the level of contamination of the beluga whales in this coastal marine ecosystem has not decreased ten years after regulating the use of TBT‐based antifoulants on small craft. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
66.
The effect of ionizing radiation on microbiological decontamination of medical herbs and biologically active compounds 总被引:1,自引:0,他引:1
W. Migdal B. Owczarczyk B. Kedzia E. Holderna-Kedzia E. Segiet-Kujawa 《Radiation Physics and Chemistry》1998,52(1-6):91-94
Several thousand tons of medical herbs are produced annually by pharmaceutical industry in Poland. This product should be of highest quality and microbial purity. Recently, chemical methods of decontamination are recognized as less safe, thus irradiation technique was chosen to replace them in use. In the Institute of Nuclear Chemistry and Technology the national program on the application of irradiation to the decontamination of medical herbs is in progress now. The purpose of the program is to elaborate, on the basis of research work, the facility standards and technological instructions indispensable for the practice of radiation technology. 相似文献
67.
A model for the dynamics of isothermal absorption of a binary mixture of an organic substance, soluble in water, and water
vapor in a fixed bed of activated carbon was proposed. It includes the equations of material balance and the Myers—Prausnitz
model for equilibrium adsorption. The possibility of formation of the condensed phase during the adsorption of an organic
substance on moist activated carbon was shown.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1491–1495, August, 1998. 相似文献
68.
M. V. Kulikov 《Russian Chemical Bulletin》1998,47(12):2399-2403
The specific heat capacities of hexamethylphosphoric triamide, diethylpropionamide, their aqueous solutions, and mixtures
of hexamethylphosphoric triamide with formamide were measured in the temperature range from 288.15 to 318.15 K. The dependences
of the partial molar heat capacity of aqueous solutions of amides on the composition of the mixture have maxima in the region
of 0.02–0.04 molar fractions of amide. The maximum on a similar dependence for solutions of hexamethylphosphoric triamide
corresponds to the concentration of 0.01 molar fractions. The conclusion on the formation of solvates (hydrates) in the systems
studied was made. The heat capacity coefficients of pair and triple interactions were calculated in terms of the McMillan-Mayer
theory. A change in the heat capacity characteristics with the temperature change was analyzed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2479–2483, December, 1998. 相似文献
69.
Development and validation of a capillary electrophoresis method for determination of enantiomeric purity and related substances of esomeprazole in raw material and pellets 下载免费PDF全文
Pablo Estevez Sabrina Flor Oriana Boscolo Valeria Tripodi Silvia Lucangioli 《Electrophoresis》2014,35(6):804-810
A capillary electrophoresis method using CDs for quality control of esomeprazole (ESO) in terms of enantiomeric purity and related substances in raw material and pellets was developed. ESO is the S‐enantiomer of omeprazole (OMZ). Several parameters were evaluated, including type and concentration of buffer and CD, concentration of additives and electrolyte pH. Resolution between the enantiomers of OMZ obtained for each parameter tested was calculated and the presence of the main related substance such as OMZ sulfone was carefully monitored. The optimized system consisted of 100 mM Tris‐phosphate buffer pH 2.5 with 20 mM 2‐hydroxypropyl‐β‐CD, 1 mM sodium dithionite, temperature at 15°C, voltage at 28 kV, and UV detection at 301 nm. Once optimized, the electrophoretic system was validated according to ICH guidelines. The limits of detection and quantification for R‐OMZ were 0.6 μg/mL (0.06% w/w of ESO) and 2.0 μg/mL (0.2% w/w of ESO), respectively. A mean concentration of R‐OMZ <0.2% limit established by the United States Pharmacopeia (USP) was found in the raw material and six‐pellet samples of ESO. No other impurities were found in the samples under these conditions. Therefore, the developed method was found to be appropriate not only for enantiomeric quality control of ESO but also for the analysis of ESO and the main related substance in raw material and pharmaceutical formulations as well as for stability indicating studies. 相似文献
70.
Ren‐Qi Wang Katharina Druckenmüller Gereon Elbers Klaus Guenther Jean‐Philippe Croué 《Journal of mass spectrometry : JMS》2014,49(2):154-160
The composition and physiochemical properties of aquatic‐phase natural organic matter (NOM) are most important problems for both environmental studies and water industry. Laser desorption/ionization (LDI) mass spectrometry facilitated successful examinations of NOM, as humic and fulvic acids in NOM are readily ionized by the nitrogen laser. In this study, hydrophobic NOMs (HPO NOMs) from river, reservoir and waste water were characterized by this technique. The effect of analytical variables like concentration, solvent composition and laser energy was investigated. The exact masses of small molecular NOM moieties in the range of 200–1200 m/z were determined in reflectron mode. In addition, spectra of post‐source‐decay experiments in this range showed that some compounds from different natural NOMs had the same fragmental ions. In the large mass range of 1200–15 000 Da, macromolecules and their aggregates were found in HPO NOMs from natural waters. Highly humic HPO exhibited mass peaks larger than 8000 Da. On the other hand, the waste water and reservoir water mainly had relatively smaller molecules of about 2000 Da. The LDI‐MS measurements indicated that highly humic river waters were able to form large aggregates and membrane foulants, while the HPO NOMs from waste water and reservoir water were unlikely to form large aggregates. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献