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61.
Fused silica capillaries deactivated with D4 and coated with OV-1 were subjected to cobalt-60 gamma radiation in order to elucidate the effect of incident radiation on column performance. The chromatographic performance of these open tubular columns in which OV-1 was polymerized in situ was found to be dependent on the dosage of radiation and was evaluated before and after the irradiated columns were rinsed with solvent. Of the radiation dosages employed, 3 MRad produced superior chromatographic performance coupled with very favorable residual surface activity. 相似文献
62.
Summary Al2O3-PLOT columns are used with great advantage for the analysis of volatiles, because of the increased capacity ratio and selectivity compared to WCOT-columns. Their applicability is limited to relatively non-polar components with relatively low boiling points i. e. eluting before n-decane.In the analysis of the halocarbons in stratospheric air, the decomposition of certain compounds was observed. In this study the stability of a number of volatile organic compounds was determined in function dependence of the column temperature using a two-dimensional GC-system.A possible reaction mechanism for the decomposition is proposed and confirmed for several chlorinated ethanes. 相似文献
63.
I. M. Mutton 《Chromatographia》1998,47(5-6):291-298
Summary Rapid analyses were performed using reversed-phase liquid chromatography with short (20–100 mm) columns swept by fast yet
shallow gradients, and the results compared with those obtained with 150 mm columns and slow gradients. The resolution losses
incurred with shorter columns were minimised by employing elevated flow rates, to ensure that comparable mean retention factors
were experienced by individual analytes during gradients run on different columns. This conserves gradient steepness. High
quality performance was obtained with turn-around times of 5–10 minutes. An overall 5-fold enhancement in the rate of information
generation was obtained. The relevance of instrumental parameters and of column and packing dimensions, upon the potential
for improved performance is discussed. Some implications for the rapidly developing technique of capillary electrochromatography
are briefly indicated. 相似文献
64.
M. Baru A. Danilov I. Vagenina E. Gorbunova S. Moshnikov L. Mustaeva V. Cherskii 《Chromatographia》1997,45(1):351-354
Summary The design of new dynamic, axial-compression columns with a system for continous packed bed adjustment and monitoring of the
floating adapter position is described. The columns are meant for liquid chromatography at low pressures (up to 8 bar) in
aqueous and organic media with stationary phases of all types. The columns have adapter position pickups for continuous automatic
monitoring of the bed height (original “swellographic” monitoring). The column described with gas pressurisation was tested
with soft Sephadex G-10 and G-25. In spite of the reduction in external porosity there was no dramatic increase in back-pressure.
The column proved to provide long-term stability of the packed bed and improvement in resolution.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
65.
Xiong Wen Ye Yu Ping Zhang Ling Bo Qu Li Qun Fan Bo Li 《中国化学快报》2007,18(11):1399-1402
Microwave irradiation was firstly attempted for the preparation of organic-based monoliths of poly(styrene-divinylbenzene- methacrylic acid), which single step in situ polymerization was carried out during 15 min. The colunm permeability, electrophoretic and chromatographac behaviors were comparatively evaluated using pressure-assisted CEC, GEC and low pressure-driven separation modes. The largest theoretical plates for the preparing column could be close to 18,0000 plates/m for thiourea in the mode of p-CEC. It provided a viable alternative to traditional initiation means for the perparation of monolithic capillary columns. 相似文献
66.
The Saccharomyces strains uvarum, montuliensis, bayanus, capensis and florentinus were grown in liquid media prepared from a 1% aqueous glucose solution to which 0.05% of ammonium sulfate or urea were added as the only nitrogen supply. The amino acids exuded during incubation were isolated by cation exchange and derivatized as the corresponding N,O-heptafluorobutyryl isopropyl esters. Separation was achieved on a highly deactivated glass capillary column coated with OV-101. A characteristic amino acid profile was obtained for each of the species studied, allowing the construction of a chemotaxonomic tree, on the basis of present or absent acids. 相似文献
67.
68.
Preparation of a sulfonated fused-silica capillary and its application in capillary electrophoresis and electrochromatography 总被引:1,自引:0,他引:1
In the present paper, two new methods, sol-gel and chemical bonding methods, were proposed for preparation of sulfonated fused-silica capillaries. In the sol-gel method, a fused-silica capillary was coated with the sol solution obtained by hydrolysis of 3-mercaptopropyltrimethoxysilane (MPTS) and tetramethoxysilane, and followed by age; while in the chemical bonding method, a capillary was chemically bonded directly with MPTS. Then, both the resulting capillaries were oxidized with an aqueous solution of hydrogen peroxide solution (H2O2) (30%, m/m) to obtain the sulfonated capillaries. The electroosmotic flow (EOF) for the sulfonated capillaries was found to remain almost constant within the studied pH range, and greater than that of the uncoated capillary. However, the coating efficiency of the capillary prepared by chemical bonding method was higher than that by sol-gel method, by comparing their magnitude of the EOF, the degree of disguise of the silanol and reproducibility of preparation procedure. The effects of the electrolyte's concentration and the content of methanol (MeOH) on the EOF were also studied. Especially, the study of the apparent pH (pH*) on the EOF in a water-MeOH system was reported. Finally, capillary electrophoretic separation of seven organic acids was achieved within 6.5 min under optimal condition using the chemically bonded sulfonated capillary. Moreover, separation of four alkaloids on the sulfonated capillary was compared with that on uncoated capillary in different conditions. Ion-exchange mechanism was found to play a key role for separation of these four basic analytes on the sulfonated capillary. 相似文献
69.
70.
Comparison between adsorption isotherm determination techniques and overloaded band profiles on four batches of monolithic columns 总被引:1,自引:0,他引:1
The adsorption isotherms of 4-tert.-butyl phenol were measured on four different monolithic columns, using three different techniques, classical frontal analysis (FA), the perturbation on a plateau method (PP) and the recently introduced numerical procedure known as the inverse numerical method (IN). This last approach requires only the recording of a few overloaded profiles and has the potential advantage of affording a dramatic decrease of the amounts of compounds, solvent, and time needed to determine accurate estimates of the coefficients of the isotherm. The reproducibility of the adsorption data measured on the four columns is discussed with reference to the specific techniques used for obtaining these data and to the most suitable equation used for modeling them. The data obtained for the different columns were highly consistent. The inverse numerical approach was confirmed to provide a powerful, accurate, and economic method for measuring single component adsorption data. 相似文献