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81.
A method has been developed for the preparation of modified silica plates for high performance thin-layer chromatography (HPTLC). Some typical organosilanes were thus allowed to react in situ with the silica of Merck HPTLC-plates. This method was found to be highly reproducible, simple and cheap. Non-polar plates were prepared and compared with commercial plates from Merck, Whatman and Macherey-Nagel. Modification with cyanodecyltrichlorosilane resulted in plates that showed good coverage, efficiency and low residual silica activity. Silica modified with a multifunctional silane has different properties in different organic solvents. It will appear to be non-polar in a polar solvent and vice versa. New advantageous separation systems are thus made feasible by the presence of cyano groups on the plate. The utility of modified thin-layer plates is demonstrated by the separation of some homologues of p-hydroxybenzoic acid esters and of some polycyclic aromatic hydrocarbons. 相似文献
82.
Monodisperse, cationic polymer particles bearing quaternary ammonium groups effectively self-organized on hydrophobic solid substrates such as alkylated glass plates and polymer films to form particle monolayers. With an increase of the particle surface charge density, the surface coverage decreased and the morphology of particle monolayers changed from aggregated type to dispersed type. The dispersed type of particle monolayers having a relatively regular particle distance was formed at higher temperature. The self-organization behaviors on alkylated glass plates were different from those on unmodified glass plates through electrostatic interaction. The formation of particle monolayers on alkylated glass plates occurred only over a certain latex concentration range in contrast with that on unmodified glass plate. The adhesive strength of particle monolayers was enhanced by annealing at temperatures above the glass transition temperature (T
g) of the particles. Lens-shaped particle monolayers were fabricated by annealing the dispersed type of particle monolayers. 相似文献
83.
O. Nilsson 《Journal of separation science》1979,2(12):720-722
Kaiser's “abt” concept rests on the experimental establishment of a linear relation between band width at half height, b0.5, and capacity ratio, k, according to His column specification quantity, hreal, is dependent on the square of the slope a, obtained from a linear regression analysis based on this relation. It is shown in the present paper that an improvement of the experimental conditions leading to a lower extra-column contribution to band broadening, b, introduces a tendency towards a negative curvature in the plot at low k values. The mean slope increases, and an uncritical linear regression would yield an hreal-value which is higher than before and which would be in the opposite direction to the requirements of a reliable column specification. Generally the linear regression analysis has to be moved to higher k regions in cases of curvature, especially as it is also shown that hreal is an estimation of the traditional HETP value, H∞, that would be obtained when k approaches infinity. This theoretically expected relation is a strong motivation for the use of hreal as a column specification, since the b0.5-value associated with H∞ is expected to be practically independent of b. 相似文献
84.
85.
Dominik Huber P. G. Anil Kumar Paul S. Pregosin Igor S. Mikhel Antonio Mezzetti 《Helvetica chimica acta》2006,89(8):1696-1715
Chloride abstraction from the half‐sandwich complexes [RuCl2(η6‐p‐cymene)(P*‐κP)] ( 2a : P* = (Sa,R,R)‐ 1a = (1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐1‐phenylethyl)]phosphoramidite; 2b : P* = (Sa,R,R)‐ 1b = (1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl bis[(1R)‐(1‐(1‐naphthalen‐1‐yl)ethyl]phosphoramidite) with (Et3O)[PF6] or Tl[PF6] gives the cationic, 18‐electron complexes dichloro(η6‐p‐cymene){(1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐phenyl]ethyl}[(1R)‐1‐phenylethyl]phosphoramidite‐κP}ruthenium(II) hexafluorophosphate ( 3a ) and [Ru(S)]‐dichloro(η6‐p‐cymene){(1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl {(1R)‐1‐[(1,2‐η)‐naphthalen‐1‐yl]ethyl}[(1R)‐1‐(naphthalen‐1‐yl)ethyl]phosphoramidite‐κP)ruthenium(II) hexafluorophosphate ( 3b ), which feature the η2‐coordination of one aryl substituent of the phosphoramidite ligand, as indicated by 1H‐, 13C‐, and 31P‐NMR spectroscopy and confirmed by an X‐ray study of 3b . Additionally, the dissociation of p‐cymene from 2a and 3a gives dichloro{(1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐(1‐(η6‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP)ruthenium(II) ( 4a ) and di‐μ‐chlorobis{(1Sa)‐[1,1′‐binaphthalene]‐2,2′‐diyl [(1R)‐1‐(η6‐phenyl)ethyl][(1R)‐1‐phenylethyl]phosphoramidite‐κP}diruthenium(II) bis(hexafluorophosphate) ( 5a ), respectively, in which one phenyl group of the N‐substituents is η6‐coordinated to the Ru‐center. Complexes 3a and 3b catalyze the asymmetric cyclopropanation of α‐methylstyrene with ethyl diazoacetate with up to 86 and 87% ee for the cis‐ and the trans‐isomers, respectively. 相似文献
86.
《Electroanalysis》2006,18(12):1173-1178
Nano‐scale zeolite Y crystals were synthesized, and palladium nanoparticles were prepared in the supercage of the zeolite by “ship‐in‐a‐bottle” approach. A novel method to fabricate zeolite‐modified electrode (ZME) loading Pd nanoparticles was developed, in which the zeolite Y loading Pd2+ ions was self‐assembled on (3‐mercaptopropyl) trimethoxysilane‐attached Au surface to form the stable and density packed multilayers (SAM‐ZME). The structures of zeolite Y and the SAM‐ZME were investigated by using TEM, XRD and SEM techniques. Pd2+ ions in the SAM‐ZME were converted into Pd nanoparticles (Pdn0) by two steps consisting of the electrochemical reduction as well as the succeeding admission and release of CO. The redox couple [Fe(CN)6]3?/4? was used to probe the electron‐transfer barrier properties during self‐assembling process. Moreover, the special properties of the SAM‐ZME loading Pdn0 were studied by using cyclic voltammetry and CO‐probe in situ FTIR spectroscopy. The results illustrated that Pdn0 in the SAM‐ZME exhibits higher electrocatalytic activity for oxidation of adsorbed CO than that of ZME prepared in our previous study by zeolite coating method. The present study is of importance in design and preparation of SAM‐ZME, which poccesseses excellent properties for the immobilization of electrocatalysts or biomolecules. 相似文献
87.
Hohyun Kim Moon Sun Jang Jung-Ae Lee Dongjin Pyo Hye-Ran Yoon Hee Joo Lee Kyung Ryul Lee 《Chromatographia》2004,60(5-6):335-339
A sensitive and selective method for the determination of sofalcone in human plasma was established by use of protein precipitation and liquid chromatography-tandem mass spectrometry. Plasma samples were transferred into 96-well plate using an automated sample handling system and spiked with 10 L of 2 g mL–1 internal standard solution (d3-sofalcone). 0.5 mL of acetonitrile was added to the 96-well plate and the plasma samples were then vortexed for 30 sec. After centrifugation, the supernatant was transferred into another 96-well plate and completely evaporated at 40 °C under a stream of nitrogen. The dry residue was reconstituted with mobile phase. All sample transfer and protein precipitation was automated through the application of both the PerkinElmer MultiPROBE II HT and TOMTEC Quadra 96 workstation. The limit of quantitation of sofalcone was 2 ng mL–1 using a sample volume of 0.2 mL for the analysis. The reproducibility of the method was evaluated by analyzing five samples at nine quality control (QC) levels over the nominal concentration range from 2 ng mL–1 to 1000 ng mL–1. Validation of the method showed that the assay has good precision and accuracy. Sofalcone and internal standard produced a protonated precursor ion ([M+H]+) at m/z 451 and 454, and both gave a corresponding product ion at m/z 315. The high sample throughput of the method has been successfully applied to a pharmacokinetic study of sofalcone in human plasma. 相似文献
88.
Summary The retention and selectivity of flavonoids (baicalin, baicalein, wogonin, oroxylin A) inScutellariae radix have been studies by high-performance thin-layer chromatography on phenyldimethylethoxysilane-treated silica plates. The silica plates treated with phenyl groups were used for physical and chemical analysis. From elemental carbon analysis, the maximum number of bonded phenyl surface groups per gram was calculated to be 0.467×1021 (Oginal silica plate: Merck Art. 15109, Silica gel 100 F254). With methanol-1/15 M phosphate buffer (pH 6.2) mixtures as mobile phase, baicalin, baicalein, wogonin, and oroxylin A inScutellariae radix were separated. It has been shown that phenyl-treated plates are more suitable for selective separation of baicalin, baicalein, wogonin, and oroxylin A than octadecyl-treated plates. 相似文献
89.
E. V. Mutseneck D. A. Loginov A. A. Pronin P. V. Petrovskii A. R. Kudinov 《Russian Chemical Bulletin》2007,56(9):1927-1929
Cationic arene complexes [Cb*Co(naphthalene)]+ (2, Cb* = C4Me4) and [Cb*Co(phenanthrene)]+ were synthesized by the reactions of [Cb*Co(MeCN)3]+ with arenes. The [Cb*Co(anthracene)]+ complex was synthesized by the abstraction of the iodide ion from [Cb*CoI]2 by TIBF4 in the presence of anthracene. Complex 2 exchanges the naphthalene ligand for other arenes at room temperature.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1861–1863, September, 2007. 相似文献
90.
WEN Yi-Hang ZHANG Jian QIN Ye-Yan LI Zhao-Ji KANG Yao CHEN Yu-Biao CHENG Jian-Kai YAO Yuan-Gen② 《结构化学》2004,(9)
1 INTRODUCTION The increasing interest in inorganic-organic hybrid framework assemblies has resulted in a great number of research efforts focused on the develop- ment of new functional materials possessing various potential applications on catalysis, electrical conduc- tivity and magnetism[1~4]. In recent years, the inter- action of H2pdc with several metal ions has been extensively studied[5, 6] due to its unique ability to form stable chelates in diverse coordination modes such as bid… 相似文献