ISSN:0935-6304    

DOI:10.1002/jhrc.1240081102

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

年代:1985

数据来源: WILEY

摘要:

AbstractA study was carried out on the effects of acid leaching of capillary column wall materials. Leaching experiments with glass and fused silica were performed under static and dynamic conditions; moreover, the influence of the temperature was investigated. The amount of water released during different temperature programs was measured with a microwave plasma detector. Different leaching conditions and column wall materials cause considerable variations in water production. These results probably explain the disappointing deactivation efficiency obtained for fused silica and dynamically leached soft glass if HMDS is used. Evidence was found for an increase in surface area due to acid leaching.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081103

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

年代:1985

数据来源: WILEY

摘要:

AbstractHigh‐temperature silylation (HTS) used for the deactivation of capillary columns was studied on the silica commonly used in HPLC to gain a better insight into this process. LiChrosorb Si 100 was silylated with disilazanes at different temperatures and the materials obtained were compared in terms of organic and silanol group surface concentration, IR reflection spectra, HPLC behavior, and pore distribution parameters. Applying diphenyltetramethyldisilazane, the volatile reaction products were monitored during the HTS process. With increasing silylation temperature up to 400°C the silanol surface concentration is reduced to a very small level independent of the organic group concentration which exhibits a broad maximum depending upon substituents and temperature. Up to 350°C triorganosiloxy groups prevail as bonded organic groups. It could be proved that HTS is accompanied by pore alterations of the silica matrix. Arguments proposed by different authors in explaining HTS effects are discus

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081104

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

年代:1985

数据来源: WILEY

摘要:

AbstractA new phenyl‐cyanopropyl polymethylsiloxane stationary phase, DB‐1301, which can be crosslinked and bonded to the fused silica surface, has been synthesized. The phase composition was optimized for the separation of 18 volatile priority pollutants, selected from the so‐called “purgables” list because of problems associated with their resolution. The composition of the stationary phase was based on theoretical considerations of binary phase mixtures and window diagram prediction. Columns coated with this stationary phase are compatible with atom selective detectors, such as the electron capture detector. A mixture of 18 volatile priority pollutants and a mixture of chlorinated pesticides were used as test probes on a prototype 30 m × 0.32 mm fused silica column, containing a 1.0 μm film

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081105

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

年代:1985

数据来源: WILEY

摘要:

AbstractCoating intensively leached silica surfaces with OH‐terminated phases provides a new way of producing, by simple means, columns with substantially increased inertness and thermostability. In addition, their separation efficiency is found to be typically higher than that of columns with traditional coatings. The underlying basic effect is a condensation process between terminal silanol groups of the phase and residual silanols, of the glass surface, thus producing the mentioned inertness. Moreover, the surface‐bonded molecules are immobilized without addition of a radical generator. If required, crosslinking can also be effected using a volatile azo compound. No vinyl groups are required for this additional immobilization process. The paper discusses all processes involved, and gives detailed working directions for the following medium polar phases. OV‐1701‐OH, OV‐31‐OH (new, 17% cyanopropyl), OV‐61‐OH, and OV‐17‐OH, and the apolar phases PS‐347.5 and PS‐086. There is no doubt so far that the principle of terminal silanol groups is applicable to all silicone phases, and may replace the traditional endcapped stationa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081106

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

年代:1985

数据来源: WILEY

摘要:

AbstractHPLC fractions involving eluents of low to intermediate polarity can be introduced into capillary GC using the retention gap technique. Partial or complete solvent evaporation during sample introduction reduces the length of, or almost eliminates, the zone in the column inlet (retention gap) flooded by the introduced liquid, allowing introduction of larger HPLC fractions and/or use of shorter retention gaps. The corresponding techniques are reviewed. The retention gap technique is poorly suited for water‐containing HPLC eluents (reversed phase HPLC) and fails completely if HPLC eluents contain,e.g., buffer salts. Various techniques for extracting such HPLC eluents are considered, preference being given to extraction into GC stationary phases from where solutes are thermally desorbed into the GC separation column. Limiting factors are diffusion of solutes within the liquid phase to be extracted and retention power of the extraction tube

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081107

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe applicability of capillary columns for gas chromatography is often limited by stationary phase degradation at elevated temperatures. In order to achieve a better understanding of column thermostability, column bleed products have been analyzed qualitatively by gas chromatography‐mass spectrometry (GC‐MS). Three silicone stationary phases were studied: SE‐52, SE‐54, and OV‐1701. Each of these was immobilized in the columns. The proportion of cyclics containing diphenyl in column bleed from SE‐52 reflected to a large extent the composition of the polymer, while for SE‐54 the proportion of such cyclics was unexpectedly high. The polar moiety of OV‐1701, the cyanopropyl(phenyl)siloxy unit, was found to exert a highly destabilizing effect on the polymer, and the thermal degradation products consisted mainly of cyclosiloxanes conta

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081108

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

年代:1985

数据来源: WILEY

摘要:

AbstractA method is described for surface deactivation and modification of fused silica capillary columns with a cyanopropyl‐containing reagent. The deactivation procedure involved a dehydrocondensation reaction between a bis(cyanopropyl)methylhydropolysiloxane reagent and surface silanol groups at an optimum temperature of only 250°C. Actual critical surface tension measurements were made using the capillary rise method. Excellent deactivation for acidic and basic compounds at the low ng level, and wettability for nonpolar and polar polysiloxane stationary phases were obtained. A procedure was developed to remove acidic impurities that are present in polar stationary phas

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081109

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

年代:1985

数据来源: WILEY

摘要:

AbstractA principal components multivariable statistical method based on SIMCA 3B (Soft Independent Method of Class Analogy) algorithms was evaluated and applied to interpretation of homolog‐specific analysis of polychlorinated biphenyls by high resolution gas chromatography. High resolution gas chromatograms can be evaluated in high resolution separations of individual PCB isomers and grouped into the homologous series. The chromatograms show distinct differences between PCB compositions with different contents of chlorine atoms in technical mixtures (Aroclors). The objective of utilizing SIMCA 3B was its evaluation for a possible identification, classification, and categorization of Aroclors in environmental sample

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081110

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

年代:1985

数据来源: WILEY

摘要:

AbstractA system for automatic analysis of volatile compounds by purge‐and‐cold‐trapping/capillary gas chromatography is described. It is suitable for analysis of volatile compounds in a wide variety of samples, such as water, food products and environmental samples. Possibilities and limitations of the system are evaluated in relation to several parameters. The efficiency of different types of cryogenic trap (open tubular, coated, packed) is also investigated; it depends on purge‐flow rate, temperature of trapping, and total purge volume. Examples of the analysis of volatile compounds in foods and water ar

ISSN:0935-6304    

DOI:10.1002/jhrc.1240081111

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

年代:1985

数据来源: WILEY