Inert-fused silica capillary columns

The use of a fused silica capillary column for the GC analysis of the neutral oil extract has provided the means for improving the resolution of components in a more inert system. The sultones are determined by temperature-programmed GC over CP-Sil-5 CB (methyl silicone fluid) in a 25 m x 0.2 mm fused silica capillary column using nonadecane as internal standard. A sample split ratio of 1 100 is recommended for a 3-pl injection. 

After quenching a sample of the product mixture with a minimum amount of brine, or after distilling off all the volatile components into a cold ( -79"C) receiver, the composition of the reaction mixture is analyzed by gas chromatography on a fused silica capillary column, using u-oclane (usually) as an internal standard. Samples to be analyzed are conveniently stored in small vials closed with a Mini-inert valve made of Teflon. 

Fig. 5.1. Gas chromatography (GC) profile of ethyl ester of purified 0-trans, 2-cis CLA isomer (a) before and (b) after heating to 220°C in an inert atmosphere for 2 h. The process caused isomerization into the isomer 11-c/s,13-frans by thermal [1,5] sigmatropic hydrogen shift. GC conditions 100-m CP Sil 88 fused silica capillary column and flame ionization detection (FID).

The first advantage of fused-silica capillary columns as compared with glass columns is their inertness, although they still require deactivation. 

The introduction of inert fused-silica capillary colunms in 1979 markedly changed the practice of gas chromatography, enabling high-resolution separations to be performed in most laboratories (1,2). Previously, such separations were achieved with reactive stainless steel columns and with glass colunms. After 1979, the use of packed colunms began to decline. A further decrease in the use of packed colunms occurred in 1983 with the arrival of the megabore capillary colunm of... 

In addition to providing a separation where peaks have narrower bandwidths compared to those of a packed column counterpart, a properly prepared fused-silica capillary column, which has an inert surface (less potential for adverse adsorptive effects toward polar species), yields better peak shapes (i.e., bands are sharper with less peak tailing), which facilitates trace analysis as well as providing more... 

Gas chromatography possesses inherent advantages that make it particularly attractive for the characterization and quantitative analysis of terpene mixtures. These include high separation efficiencies, short residence times in the chromatographic column, and the use of an inert atmosphere during analysis, the lack of azeotropes, and applicability to very small samples. In most cases capallaiy columns with dimethyl polysiloxane (methyl silicone) nonpolar and Carbowax 20M pwlar phases are used. Carbowax 20M phases include DB Wax, BP-20, PEG 20M and HP 20, while methyl silicone phases include SE-30, SF-%, OV-1, OV 101, BP 1, CPSIL 5CB, SP 2100, DB 1, DB 5 and HP 1 (Davies, 1990). Among these fused-silica capillary GC columns, DB 1 or DB 5 and CPSil 5 are usually preferred. 

Dynamic in-tube SPME In this system, we assume the use of a piece of fused silica capillary, internally coated with a thin film of extracting phase (a piece of open tubular capillary gas chromatography (GC) column), or that the capillary is packed with extracting phase dispersed on an inert supporting material (a piece of micro-LC capillary column). 

The development of the flexible fused silica capillary GC column described in Section 11.5 resulted in the domination of the GC market by open tubular columns and instruments tailored to their use. Packed columns are relegated to a few special applications. Fused silica capillaries were easy to install. They were more inert (i.e., contained less active sites causing tailing) than glass or metal capillaries or the particle supports used in packed column GC. Even when the resolution of packed columns was sufficient for simple separations, a capillary coated with the same stationary phase could... 

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