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排序方式: 共有501条查询结果,搜索用时 15 毫秒
1.
Nováková Kateřina Hrdlička Vojtěch Navrátil Tomáš Vyskočil Vlastimil Barek Jiří 《Monatshefte für Chemie / Chemical Monthly》2015,146(5):761-769
Monatshefte für Chemie - Chemical Monthly - The voltammetric behavior of 5-nitroindazole was investigated at polished (p-AgSAE) and at mercury meniscus-modified (m-AgSAE) silver solid amalgam... 相似文献
2.
A practical Sonogashira alkynylation protocol for the preparation of 8-alkynylated adenosines and guanosines has been developed. Protection of the sugar hydroxyl substituents is not required; protection hinders the purification of these products. A preliminary fluorescent study is reported, which shows that the presence of a substituent on the phenylene ring influences the fluorescent properties considerably, an outcome that could be utilized in biological applications. 相似文献
3.
Neutron irradiation of Cp2MoCl2 for 24 h afforded the radiotracer Cp299MoCl2 which was characterised by UV–Vis spectroscopy and thin layer chromatography. Binding experiments with the thiol containing protein human serum albumin (HSA) or calf thymus DNA, were monitored for 99Mo using a gamma counter. Under the conditions investigated, molar ratios of binding of 0.2:1 (Cp2MoCl2:DNA) and 9.4:1 (Cp2MoCl2:HSA) were calculated. The results are consistent with in vitro coordination studies that have shown strong preferential interaction of Cp2MoCl2 with thiols versus other donor sites in biomolecules including DNA. 相似文献
4.
5.
Su-Yun Huang Chuhsing Kate Hsiao Ching-Wei Chang 《Annals of the Institute of Statistical Mathematics》2003,55(3):655-670
The article provides a refinement for the volume-corrected Laplace-Metropolis estimator of the marginal likelihood of DiCiccioet al. The correction volume of probability α in DiCiccioet al. is fixed and suggested to take the value α=0.05. In this article α is selected based on an asymptotic analysis to minimize
the mean square relative error (MSRE). This optimal choice of α is shown to be invariant under linear transformations. The
invariance property leads to easy implementation for multivariate problems. An implementation procedure is provided for practical
use. A simulation study and a real data example are presented. 相似文献
6.
Kate B. Poiesz Carol L. Grundner Nancy L. Redman-Furey 《Journal of Thermal Analysis and Calorimetry》2006,85(1):79-86
Characterization of the solid-state form (hydrate
or polymorph) of a pharmaceutical active is a key scientific and regulatory
requirement during development of and prior to seeking approval for marketing
of the drug product. A variety of analytical methods are available to perform
this task. By nature of the fundamental information it provides, TG-DTA offers
advantages over other methods in regards to monitoring and quantitation of
hydration state changes. In a single experiment with only a few milligrams
of sample, TG-DTA perceives minor changes in phase, quantitates total water
content and percent conversion, and illustrates hydrate type. All of this
is accomplished without the necessity of generating time-consuming standard
curves representing the differing ratios of hydrated to anhydrous forms. This
study describes the use of TG-DTA to monitor and quantitate humidity induced
solid–solid phase conversion of nitrofurantoin and risedronate. Percent
conversion was qualitatively observed by both TG and DTA signals and quantitated
by the TG. 相似文献
7.
Flow injection spectrofluorimetry with in-line Winklers procedure was developed for the dissolved oxygen (DO) determination. 2-Thionaphthol reacted with iodine produced by Winkler’s method to form fluorescence inactive disulfide compound. To automate the process completely, a 5-channel flow system with a newly designed 16-way valve was assembled. The system consisted of a dispersion coil (DC), a precipitate formation coil (PFC), a precipitate dissolving coil (PDC), and extraction coil (EC). A calibration can be constructed by using a standard iodine solution for dissolved oxygen. The calibration graph was linear over the range 1.2×10−4∼6.0×10−4 mol l−1 iodine (1.96∼9.80 mg O l−1)). The relative standard deviation (n=6) was below 0.3% for the 4×10−4 mol l−1 iodine (6.27 mg O l−1) determination. The sample throughput was 12/h. 相似文献
8.
Kate J. Graham Chris P. Schaller Brian J. Johnson John B. Klassen 《The Chemical Educator》2002,7(6):376-378
The incorporation of research projects into undergraduate chemistry courses provides a perspective that is fundamentally unavailable in most laboratory experiences. While independent, multistep synthesis projects in organic chemistry have been reported previously, most efforts have been directed at relatively restricted, closely guided research plans with modest student participation in the experimental design. We have implemented a more open-ended synthesis project, limited principally by cost, safety and availability of materials. In the second semester of the sophomore organic sequence, students develop multiple drafts of a plan for a three-to-four-step synthesis. Subsequently, students obtain their own literature protocols for the individual steps. The synthesis is performed over three four-hour laboratory periods. The students conclude this project with a poster presentation of the results at the end of the semester. Evaluation of the students work focuses not only on the successful synthesis of the target but also on planning, troubleshooting, purification, and spectral analysis. 相似文献
9.
2-[2-(5-Bromopyridyl)azol-4,5-dimethylphenol (BrPDMP) and 2-[2-benzothiazolylazo)-5-dimethylaminophenol (BTADAP) have been synthesised and compared, as reagents for cadmium, with the related dyes BrPADAP and BTDMP. The new dyes both form stable highly coloured 2:1 complexes with cadmium, with molar absorptivities (in o-xylene solution) of 3.8 x 10(4) 1.mole(-1).cm(-1) at 590 nm (BrPDMP) and 4.5 x 10(4) 1.mole(-1).cm(-1) at 600 nm (BTADAP). Cadmium can be determined by extraction under alkaline conditions with a solution of BTADAP in xylene. Beer's law is obeyed up to at least 16 mug of cadmium. A limit of detection of 0.15 mug has been estimated and a coefficient of variation of 3.3% at the 5 mug level was found. The only species which interfere seriously are Co(2+), Ni(2+), and Ca(2+). A 200-fold excess of zinc may be tolerated. The method has been applied to the determination of cadmium in water samples, plant materials and hair. Interferences were overcome by preliminary extraction into Aliquat/carbon tetrachloride. The acid dissociation constant of BTADAP (pK = 9.5) and formation constant of the cadmium-BTADAP complex (log beta = 15.1) have been determined. 相似文献
10.
Kritsana Jitmanee Jaroon Jakmunee Somchai Lapanantnoppakhun Sunanta Wangkarn Norio Teshima Tadao Sakai Gary D. Christian Kate Grudpan 《Microchemical Journal》2007,86(2):195-203
Derivative techniques for analytical signal processing are useful for solving some noise and signal resolution problems in various fields of study such as titrimetry, spectrophotometry, chromatography and electrochemistry. The broad use of these techniques, however, is often limited by costly inflexible built-in software packages in commercial analytical instruments. We propose here the application of commercial simple software packages such as Microsoft® Excel and Microcal Origin for signal smoothing and fitting, and for obtaining derivative analytical signals in batch and flow-based analyses, including potentiometric titration, spectrophotometry, chromatography, voltammetry and sequential injection analysis (SIA). The worldwide (especially Excel) software packages are easy-to-use for less experienced users and have also capabilities for advanced users, and therefore employing such packages can result in expansion of useful derivative techniques. We demonstrate application of the available package-aided derivative capabilities for enhancing some chemical analyses, including potentiometric acid–base titration, Bradford assay of protein, chromatographic separation of ajmaline and reserpine and anodic stripping voltammetry of copper. The derivative signals from smoothed and fitted curves offer better accuracy and precision, even for non-resolving peaks and tailing peaks. In some cases, the optimization of experimental conditions is not further required, which can lead to fast method development. 相似文献