High-temperature capillary

One drawback of high-temperature GC analysis is that sample degradation for the high molecular weight AEs and APEOs might occur. High-temperature capillary columns are coated with a stabilised bonded polysiloxane film, which allows a column oven temperature of up to 400°C. 

The five main requirements for conduct of a sessile drop experiment relevant to high temperature capillary phenomena are characterisation of the materials, a flat horizontal substrate, a test chamber to provide a controlled and generally inert gaseous environment, a facility that heats the sample to a predetermined temperature and a means of measuring the geometry and size of the sessile drop. Satisfying these requirements demands careful and precise experimental procedures. 

The process depends on a liquid metal flowing over surfaces to form a fillet between components and into the gap between the components, and then solidifying to form a permanent bond. Thus it is essential that the braze experiences high temperature capillary attraction. Without such attraction, solid braze material placed between components will flow out of the gap, sweat , when it melts. Any residue of non-wetting liquid that remains within the gap will not conform to the microscopic features of the component surfaces but form an array of voids, as illustrated schematically in Figure 10.1, that is mechanically deleterious and should be avoided if at all possible. The size of such voids can be decreased if an external pressure is used to confine a non-wetting liquid braze into a gap but cannot eliminate them because the pressure needed to shrink voids increases as they become smaller. 

Heath D., Moffatt R. L., and Rowland S. (1995) Quantification of the C30+ fraction of North Sea gas condensates by high temperature capillary gas chromatography. Anal Proc. 32, 485-487. 

The thermal stability of the high-temperature capillary columns allowed the analysis of higher molecular masses (more than 600 Das) and nonvolatile compounds never before directly analyzed by gas chromatography [2]. 

There are four major types of materials being utilized to prepare columns for high-temperature capillary columns [2] ... 

Verzele et al.2 concluded that the "cold on-column" injection, applied for the piperine assay, and the "falling needle" injection, applied for the quinine-quinidine assay, are the best alternative at the moment for quantitative capillary gas chromatography. They are applicable to high temperature capillary gas chromatography, but they also have their limitations. 

C. Use of an O2 scrubber on carrier gas line is essential for electron capture detector recommended for high temperature capillary columns. 

Among aU chromatographic techniques that can be applied for the separation and identification of polymer additives after the extraction step, high-temperature capillary gas chromatography (CGC), " high-performance liquid chromatography supercritical fluid chro-... 

Utterback and co-workers [54] determined oligomers of polyoxymethylene glycols and ethers by derivatisation with ammonia then determination by capillary column GC. Okada [55] used temperature programmed GC to determine polymethylene oligomers. High temperature capillary GC has also been used to determine separate Novoloc phenolic and epoxy novolac oligomers [56]. 

There are number of application areas requiring columns to be operated at or above 400°C, such as the analysis of waxes, crude oils, and triglycerides. These have driven efforts to replace the polyimide outer coating with a thin (20-mm) layer of aluminum and extend the temperature range of capillary gas chromatography, as illustrated in the chromatograms of high-temperature capillary separations... 

Upler, A. and Johnson, G.L. (1989) Optimization of Conditions for High Temperature Capillary Gas Chromatography Using a Split-Mode Programmable Temperature Vaporizing Injection System, in... 

Unsulfonated linear alkylbenzene and linear alkylbenzene sulfones are the main components of unsulfated matter in linear alkylbenzenesulfonate, an anionic surfactant. These residual products can be quantified by high-temperature capillary GC and its application to alkylbenzenesulfonate improves its synthesis process (Molever, 2005). 

Sandra, R, F. David, Microcolumn chromatography for the analysis of detergents and lubricants. Part 1 High temperature capillary GC and capillary supercritical fluid chromatography, J. High Resolut. Chromatogr., 1990, 75,414-417. 

Packed-column GC analysis without derivitization is not suitable for quantitative analysis of APE, since only the first few oligomers elute and elution is incomplete for them. High-temperature capillary GC of underivatized APE has been demonstrated for resolution of up to about 12 ethoxy groups, but recovery was not determined and is presumably less than quantitative (78,79). 

David, F, D. R. Gere, F. Scanlon, P. Sandra, Elucidation of emulsifiers by high temperature capillary GC, Proceedings of the Riva 20th International Symposium on Capillary Chromatography, 1998. 

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