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排序方式: 共有494条查询结果,搜索用时 15 毫秒
1.
Poly(ethylene terephthalate) film was used as supporter for preparation of polyamide layer. The most convenient method of preparation was described. This layer can be cut into any size and its sensitivity is higher than the glass plate supported layer. Twenty aromatic nitro compounds were used to show the behavior of polyester film based polyamide layer. 相似文献
2.
3.
A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3delta-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results. 相似文献
4.
In the photovoltaic industry the etching of silicon in HF/HNO3 solutions is a decisive process for cleaning wafer surfaces or to produce certain surface morphologies like polishing or texturization. With regard to cost efficiency, a maximal utilisation of etch baths in combination with highest quality and accuracy is strived. To provide an etch bath control realised by a replenishment with concentrated acids the main constituents of these HF/HNO3 etch solutions including the reaction product H2SiF6 have to be analysed. Two new methods for the determination of the total fluoride content in an acidic etch solution based on the precipitation titration with La(NO3)3 are presented within this paper. The first method bases on the proper choice of the reaction conditions, since free fluoride ions have to be liberated from HF and H2SiF6 at the same time to be detected by a fluoride ion-selective electrode (F-ISE). Therefore, the sample is adjusted to a pH of 8 for total cleavage of the SiF62− anion and titrated in absence of buffers. In a second method, the titration with La(NO3)3 is followed by a change of the pH-value using a HF resistant glass-electrode. Both methods provide consistent values, whereas the analysis is fast and accurate, and thus, applicable for industrial process control. 相似文献
5.
Understanding molecular orientation on a metal surface is key to designing molecular electronic device junctions. Though platinum device electrodes are of particular interest as a more stable alternative to the often used gold electrodes, the chemisorption of conducting molecules onto platinum surfaces has not been thoroughly studied. We present herein the first detailed study of the ability and manner in which soluble oligothiophene isocyanides, of lengths ranging from 2 to 7 nm, chemisorb onto platinum surfaces and nanoparticles. It was found that these oligothiophene isocyanides stand at a 41 degrees angle from the platinum surface normal, suggesting their applicability in molecule-bridged platinum electrode devices. 相似文献
6.
Rudzevich Y Vysotsky MO Bohmer V Brody MS Rebek Jr J Broda F Thondorf I 《Organic & biomolecular chemistry》2004,2(21):3080-3084
The dimerization of tetratolyl- and tetratosyl-urea derivatives 1 and 2, derived from a tetrapentoxy calix[4]arene in the cone conformation and of the corresponding tetra-urea derivatives 3 and 4, in which the cone conformation is rigidified by the two crown-3 tethers, have been studied. All six possible equimolar mixtures were examined by 1H NMR using CDCl3 and CD2Cl2 as solvents. While no heterodimers are found for the combinations 1/3 and 2/4 in either solvent, all remaining combinations lead to the (exclusive) formation of heterodimers in CD2Cl2. In CDCl3 heterodimers are only observed for the combinations of 3 with 2 or 4. These results are discussed in terms of entropic and enthalpic contributions and compared with MD-simulations in a box of chloroform solvent molecules. 相似文献
7.
M. E. Niyazymbetov B. Kostizella I. Keitel K. H. Schwartz 《Russian Chemical Bulletin》1991,40(1):182-186
The cathodic electrolysis of aliphatic alcohols and alkylphosphonates in acetonitrile with 0.5 N Et4NClO4 as the base electrolyte leads to mono- and ditransesterified phosphonates. The yield and ratio of these products is a function of the nature of the starting reagents and amount of current passed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 200–204, January, 1991. 相似文献
8.
Iris Reimann Steffen Mergemeier Ingo Ebner Fritz Scholz 《Fresenius' Journal of Analytical Chemistry》1995,353(2):206-210
A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results. 相似文献
9.
A new method was developed for the analysis of pesticide residues in tobacco. The objective was to significantly increase the number of samples that can be processed by the laboratory and to enable the extension of the current coverage to additional pesticides. A new analytical approach was therefore defined based on two main axes, the automation of the sample preparation and the selectivity of the analyte detection using tandem mass spectrometry. This latter aspect reduces the stringency of the requirements placed on the clean-up of the extracts and on the chromatographic resolution when less selective detectors are used. The extraction of the analytes from the matrix is performed using the pressurized liquid extraction technique. Tobacco samples are extracted at elevated temperature and pressure (100 C and 100 atm; 1 atm = 101,325 Pa) using acetone as an extraction solvent. The resulting extract is then concentrated using a Vortex evaporator. Three different solid-phase extraction (SPE) procedures, adjusted to the chemical properties of the different active ingredients to be measured, are applied to the concentrated extract, thus leading to three extract fractions. The first fraction contains such main classes of active ingredients as organohalogenated and 2,6-dinitroaniline compounds while the second one collects the organophosphorus and acylalanines residues; these two fractions are analyzed by capillary gas chromatography coupled to tandem mass spectrometry using negative chemical ionization and electron impact ionization in the positive mode, respectively. The third extract fraction gathers the N-methylcarbamates residues which are analyzed by HPLC with post-column derivatization and fluorescence detection. The different sample preparation stages from extraction to SPE clean-up have been automated through the use of recent analytical technologies. In combination with the analysis by tandem mass spectrometry, this provided a potential for a high sample throughput. 相似文献
10.
Iris A. Bermejo Claudio D. Navo Jorge Castro-Lpez Ana Guerreiro Ester Jimnez-Moreno Elena M. Snchez Fernndez Fayna García-Martín Hiroshi Hinou Shin-Ichiro Nishimura Jos M. García Fernndez Carmen Ortiz Mellet Alberto Avenoza Jesús H. Busto Gonalo J. L. Bernardes Ramn Hurtado-Guerrero Jesús M. Peregrina Francisco Corzana 《Chemical science》2020,11(15):3996
The Tn antigen (GalNAc-α-1-O-Thr/Ser) is a well-known tumor-associated carbohydrate determinant. The use of glycopeptides that incorporate this structure has become a significant and promising niche of research owing to their potential use as anticancer vaccines. Herein, the conformational preferences of a glycopeptide with an unnatural Tn antigen, characterized by a threonine decorated with an sp2-iminosugar-type α-GalNAc mimic, have been studied both in solution, by combining NMR spectroscopy and molecular dynamics simulations, and in the solid state bound to an anti-mucin-1 (MUC1) antibody, by X-ray crystallography. The Tn surrogate can mimic the main conformer sampled by the natural antigen in solution and exhibits high affinity towards anti-MUC1 antibodies. Encouraged by these data, a cancer vaccine candidate based on this unnatural glycopeptide and conjugated to the carrier protein Keyhole Limpet Hemocyanin (KLH) has been prepared and tested in mice. Significantly, the experiments in vivo have proved that this vaccine elicits higher levels of specific anti-MUC1 IgG antibodies than the analog that bears the natural Tn antigen and that the elicited antibodies recognize human breast cancer cells with high selectivity. Altogether, we compile evidence to confirm that the presentation of the antigen, both in solution and in the bound state, plays a critical role in the efficacy of the designed cancer vaccines. Moreover, the outcomes derived from this vaccine prove that there is room for exploring further adjustments at the carbohydrate level that could contribute to designing more efficient cancer vaccines.An anti-cancer vaccine based on an unnatural antigen with an sp2-iminosugar fragment. 相似文献