摘要:

AbstractThe effect of temperature, water content, and the type of reagent on the silylation of fused silica capillaries was studied by29Si and13C CP‐MAS NMR. Fumed silica (Cab‐O‐Sil M5), which is essentially a highly dispersed vitreous quartz with a surface comparable to that of fused silica capillary columns, was selected as a model material.Hexamethyldisilazane (HMDS) and 1,2‐diphenyl‐1,1,3,3‐tetraphenyldisilazane (DPTMDS), which were used as silylation reagents, yielded trimethyl‐ and dimethylphenylsilyl surface groups respectively at lower temperatures (<350°C and<250°C respectively). At higher temperatures, increasingly more dimethylsilyl groups are formed, with the silicon bound to two oxygen atoms. This process occurs for DPTMDS at a considerably lower temperature than for HMDS. The formation of silyl groups on the surface and the disappearance of hydroxyl groups are followed independently. The13C NMR and GC‐MS of the reaction products showed that with DPTMDS, the formation of two Si‐O‐Si links is accompanied by a loss of phenyl groups rather than of methyl groups.After the Cab‐O‐Sil had been dried over P2O5, the formation of these double links occurred for HMDS only at temperatures above 460°C and for DPTMDS at 400°C. Thus we concluded that water supplies oxygen atoms for double Si‐O‐Si links (possibly crosslinks) necessary for efficient deactivation. This may explain the less successful silanization of fused silica capillaries because their water content is lower

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe original plate model of chromatography is extended to the sorption process occurring at the column inlet and the desorption process at the column exit. At the column inlet it is shown that sufficiently wide feed bands undergo no change in concentration but a fall in band width,i.e., the volume of mobile phase occupied by the solute band is reduced. The reduction factor is (1 + k) where k is the mass distribution ratio (capacity factor). Narrower bands suffer partial reduction in both band width and concentration. On desorption at the outlet, however, the change is always in band width and not concentration. A perfect detector registers the true concentration‐time profile of the band in the column if the solute mass fraction in the stationary phase is below 10−3at the column outlet. The risks of stripping the stationary phase at high solute concentrations in analytical and preparative or production gas chromatography are compa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractBorosilicate glass capillaries, silylated and coated with OV‐1 or SE‐54, were irradiated by a60Co gamma source. The effect of radiation on chromatographic performance was determined for a series of dosages and was evaluated before and after rinsing with solvent. Results for both regular and thick films were obtai

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThis article describes a method that assists in structure determination of cyclic sulfides mixtures by GC/MS. The method involves the use of a gas‐phase hydrodesulfurization microreactor (AP‐56 catalyst, reaction temperture 300‐315°C, hydrogen as a carrier and reagent gas) located between the capillary column (OV‐17) and the mass spectrometer. The presence of a microreactor in such a position does not essentially affect the chromatographic separation achieved by using the capillary column. Combined analysis of the mass spectra registered for the original sulfides and the hydrodesulfurization products permits the structure determination of each effluent to be made more reliably. This is illustrated by the investigation of a reaction mixture containing the structural and geometric isomers of methyl‐substituted thiabicy

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240071111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY