Biomecular quenching in the adsorbed layer

The influence of heat treatment and of added coadsorbates on the surface photochemistry of pyrene and 1,2-benzanthracene on aerosil is reported. It is pointed out that the surface plays an active role in determining the primary quenching processes.     

No intrinsic depletion layer on a polystyrene thin film at a water interface

Using neutron reflectivity, we found that there is no intrinsic depletion layer at a deuterated polystyrene (dPS) film and deuterium oxide (D(2)O) interface. A spun-cast film is susceptible to contamination on its surface from its surroundings during sample preparation. A contamination layer of hydrogenated organic material will be detected as a reduced scattering length density layer at the interface. We demonstrate that, by careful treatment of the film, contamination would be the primary cause of the reduced scattering length density layer at the interface.     

Validation of thin layer and high performance thin layer chromatographic methods

Analytical validation is a key requirement to asses and to prove a method's reliability and suitability for an intended use. Planar chromatographic procedures are used in different applications ranging from simple screening tests to sophisticated instrumental quantitative assays of analytes in complex matrices. This paper intends to give guidance on how to adopt international accepted formal requirements and guidelines for validation of these different TLC/HPTLC procedures. In addition, some selected parameters for robustness testing and for on going quality assurance of analytical performance based on control charts are reported.     

Resolution of optical isomers by thin layer chromatography

A process for the separation of enantiomers by TLC is described. Reversed-phase plates, pre-treated with a copper II complex of N,N-di-n-propyl-L-alanine separate all the dansyl protein amino acids, except proline, each to its D and L enantiomers.     

Determination of90Sr by thin layer radiochromatography

A simple method for the determination of⁹⁰Sr by using thin layer chromatography on silica gel or cellulose pretreated with calcium oxalate is proposed. In these conditions a complete separation between strontium and its daughter yttrium is obtained. Radioactivity of separated elements was measured by a linear multiscanner analyzer and the results were computer processed to obtain the activity of⁹⁰Sr. The method has been applied to samples of water and milk subjected to a very simple extraction procedure. Under the experimental conditions used, the detection limit is about 25 mBq of deposited radioactivity, which corresponds to about 6 Bq/l.     

Probing adsorbed fibronectin layer structure by kinetic analysis of monoclonal antibody binding

Adsorbed protein layers are often away from equilibrium and thus exhibit history dependent structures. We use the kinetics of monoclonal antibody binding, as measured using optical waveguide lightmode spectroscopy (OWLS), to investigate the structure of adsorbed fibronectin (Fn) layers formed under different kinetic paths. For all of the layers investigated, we find no difference between the apparent adsorption rate constants of (i) monoclonal antibodies specific to Fn's cell binding site (alpha-Fn) and (ii) monoclonal antibodies specific to cytochrome c (alpha-CC, as a control), indicating initial adsorption of antibodies to be non-specific. For certain layers, the saturation density and the initial projected area per antibody differ significantly between alpha-Fn and alpha-CC, suggesting specific binding to follow the initial non-specific attachment. The fraction of antibodies binding specifically to the Fn layer, and the number of Fn binding sites per specific binding event, are estimated in terms of the difference in initial projected areas between alpha-Fn and alpha-CC. For a Fn layer formed at a bulk concentration of 2 microg/mL, we find a decrease in specific binding with an increase in Fn layer formation time, suggesting post-adsorption structural changes of a lower density adsorbed layer diminish binding site availability. Conversely, for a Fn layer formed at a bulk concentration of 40 microg/mL, we find an increase in specific binding with an increase in the aging time of the Fn layer, implying post-adsorption structural changes reveal binding sites for a higher density adsorbed layer.     

Thermo-sensitive poly(DEGMMA-co-MEA) microgels: Synthesis,characterization and interfacial interaction with adsorbed protein layer

The novel microgels, poly[di(ethylene glycol) methyl ether methacrylate-co-2-methoxyethyl acrylate] poly(DEGMMA-co-MEA) microgels, were synthesized. The poly(DEGMMA-co-MEA) microgels were thermo-sensitive and exhibited a volume phase transitive temperature(VPTT) of 14–22 ?C. The incorporation of hydrophobic comonomer MEA shifted the VPTT of poly(DEGMMA-co-MEA) microgels to lower temperatures. The interfacial interaction of poly(DEGMMA-co-MEA) microgels and three model proteins, namely fibrinogen, bovine serum albumin and lysozyme, was investigated by quartz crystal microbalance(QCM). An injection sequence of "microgel-after-protein" was then established for the real-time study of the interaction of proteins and the microgels at their swollen and collapsed states by using QCM technique. The results indicated that the interfacial interaction of poly(DEGMMA-co-MEA) microgels and adsorbed protein layers was mainly determined by the electrostatic interaction. Because poly(DEGMMA-co-MEA) microgels were negatively charged in Tris-HCl buffer solution(p H = 7.4), the microgels did not adsorb on negatively charged fibrinogen and bovine serum albumin layers but strongly adsorbed on positively charged lysozyme layer. Stronger interaction between lysozyme and the microgels at collapsed state(i.e. at 37 ?C) was observed. Furthermore, the incorporation of MEA might weaken the interaction between poly(DEGMMA-co-MEA) microgels and proteins.     

Propagation of vibrational excitation in an adsorbed layer

Using a crystal model with an adsorbed layer, the propagation of vibrational excitation induced by an adsorbed particle is considered. The relaxation times of excitation have been estimated. The role of excitation transfer processes in adsorption-desorption phenomena is discussed.

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薄层色谱法检测磺胺二甲基嘧啶中杂质

建立限量检测磺胺二甲基嘧啶中杂质的方法.用薄层色谱法,使用两种展开剂系统分步同向展开对样品中的杂质进行检测.本法能简便有效地检测出磺胺二甲基嘧啶中各种可能杂质.     

Use of high-performance thin layer chromatography by the American Herbal Pharmacopoeia

TLC characterizations are among the key identity tests in most pharmacopoeial monographs. Pharmacopoeial standards are typically used by industry as a basis for meeting QC requirements and current good manufacturing practices (cGMPs). TLC is a relatively low-cost, highly versatile tool for developing specifications for raw materials, as well as for the various preparations for which pharmacopoeial standards are created. In addition to its use in the development of identity tests, TLC is a valuable tool for screening plant samples that pharmacopoeias must review in the development of monographs and botanical reference materials (BRMs). Specifically, HPTLC is the ideal TLC technique for these purposes because of its increased accuracy, reproducibility, and ability to document the results, compared with standard TLC. Because of this, HPTLC technologies are also the most appropriate TLC technique for conformity with GMPs. This article highlights the manner in which HPTLC is used by the American Herbal Pharmacopoeia (AHP) in the development of AHP monograph identity standards, the identification of adulterating species, and the development of AHP-verified BRMs.     

Corrosion monitoring of different steels by thin layer activation

For corrosion monitoring, the behavior of various steels (Sanicro 28, AISI 316 L, SAF 2507) and a carbon steel were investigated by thin layer activation (TLA) in acid solutions containing chloride. A loop system with a sample holder as well as a temperature and a flow control device were used in laboratory tests. Experimental parameters like fluid temperature, H₂SO₄ concentration and running time were selected as a function of the specific material under investigation. The congruence of TLA results was verified by comparison with mass loss data, obtained by gravimetry. This revised version was published online in July 2006 with corrections to the Cover Date.     

毒鼠强薄层色谱分析的检出限

建立薄层色谱法快速对毒鼠强进行简易分析的方法,利用薄层色谱进行层析分离,采用特殊显色方法,对毒鼠强进行显色,以能正常观察到斑点的色泽状态,辅助GC-MS方法确定检出极限。薄层色谱法分析毒鼠强检出限可达5~10μg。能用此方法对大多数中毒案件提取的检材进行定性分析。