共查询到8条相似文献,搜索用时 0 毫秒
1.
G. Rutten J. de Haan L. van de Ven A. van de Ven H. van Cruchten J. Rijks 《Journal of separation science》1985,8(10):664-672
The effect of deactivating a fused silica surface by silylation with 1,1,3,3-tetraphenyl-1,3-dimethylilazane (TPDMDS), triphenylsilylamine (TPSA), and octamethylcyclotetrasiloxane (D4) and by polydimethylsiloxane degradation (PSD) is studied. Rehydrated, dried, and deactivated Cab-O-Sil M5 samples are used as model materials for 29Si CP-MAS NMR analysis. At about 350 °C, TPDMDS yelds mainly diphenylmethylsiloxysilane, dimethyldisiloxysilane, and triphenylsiloxysilane groups. TPSA yields phenyltrisiloxysilane, diphenyldisiloxysilane, and triphenylsiloxysilane groups. At 400°C, the products formed initially are eventually replaced by methyltrisiloxysilane or phenyltrisiloxysilane groups, while a substantial number of silanol groups still remains. The possible consequences for wettability are discussed. D4 reacts with Cab-O-Sil even at 200°C, but a large number of silanol groups remains. This number decreases gradually at higher temperatures and becomes negligible above 400°C. The formation of methyltrisiloxysilane groups, which starts at 425°C, is predominant at 490°C. 相似文献
2.
J. Roeraade 《Journal of separation science》1983,6(3):140-144
An investigation of techniques suitable for precision cutting of glass and fused silica capillary tubing has been carried out. Accurate trimming of capillary tubing is important when precision splitters and manifolds have to be made. Techniques employed for cutting optical fibers proved to be useful, and factors affecting the suface quality of the fracture are discussed. It was found to be difficult to obtain a square cut with a flat surface in the case of fused silica tubing. The best results were obtained when the tubing was scored with the edge of a broken silicon wafer before the fracture was accomplished. This technique allows precision cutting of glass tubing with an outer diameter of 100 μm or less. 相似文献
3.
Summary Applications of quantitative gas chromatography/mass spectrometry (selected ion monitoring) to clinical and ecological microbiology are described. The technique permits determination of selected microbial metabolites and can be used for the rapid diagnosis of, for example, tuberculosis by ion-focusing of specific branch-chain fatty acids. The technique is also used to determine diaminopimelic and muramic acids, and D- and L-amino acids separated by chiral gas chromatography, in the low picogram range. The latter method has the potential to detect and quantitate microbial populations.Presented at the 14th International Symposium on Chromatography London, September, 1982 相似文献
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Summary This paper describes the systematic characterization of glass and the newly introduced fused silica and quartz capillary columns from surface wettability measurements. Common gas chromatographic stationary phases were used in capillary-rise measurements at temperatures up to 300°C. By construction of Zisman plots and using the Cassie equation, the relative surface concentrations of wettable and non-wettable groups were determined. By application of the Fowkes equation, the dispersion force component of the surface energy was investigated. The influence of various surface treatments such as leaching, silylation, and polymeric film formation are discussed. Wettability measurements were also used to evaluate the thermostability of various treated surfaces and to compare the surface properties of glass, quartz, and fused silica. The wettability of the surfaces with selected stationary phases as a function of temperature is also discussed. 相似文献
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The use of glass and fused silica open tubular columns for selective separation of structural, configurational, and optical isomers (enantiomers) of underivatized aliphatic alcohols and ketones by complexation gas chromatography on optically active metal chelates is described. The method represents a powerful analytical tool for the precise determination of diastereomeric (d.e.) and enantiomeric (e.e.) excesses in asymmetric syntheses and in natural product characterization. The direct screening of the enantiomeric composition and absolute configuration of terpinene-4-ol, the aggregation phermone of Polygraphus poligraphus (L), is described. 相似文献
7.
W. A. Korfmacher L. G. Rushing J. Arey B. Zielinska J. N. Pitts 《Journal of separation science》1987,10(12):641-646
This paper describes the use of high resolution capillary gas chromatography combined with negative ion atmospheric pressure ionization mass spectrometry (NIAPIMS) for the analysis of an air particulate extract for mononitropyrenes and mononitrofluoranthenes, some of which are powerful bacterial mutagens. The results are compared to those obtained by the electron impact mass spectrometric analysis of the same sample In addition, the NIAPIMS method confirmed the identification of 4-nitropyrene in the ambient air sample. 相似文献
8.
The preparation of wide bore (320 μm) and narrow bore (50 μm) fused silica capillary columns is described for immobilized cyanopropyl substituted silicones containing 60 and 88% substitution. The effect of high temperature deactivation with cyanopropylcyclosiloxanes was studied with a special test mixture. Curing was achieved with dicumyl peroxide or azo-tert-butane. The columns were evaluated and compared in terms of efficiency, activity, polarity, and temperature stability. Different coating methods were compared for the narrow bore columns. The activity of the 60% cyanopropyl columns that had been immobilized with dicumyl peroxide was significantly larger than for azo-tert-butane immobilized columns. The polarity of polar columns appeared to depend greatly on column temperature and is completely different for wide and narrow bore columns. 相似文献