Preparative gas chromatography with glass capillary columns

Abstract

SummaryThe present paper describes an automated system for preparative gas chromatography with glass capillary columns, controlled by a microprocessor. The effluent from the capillary column is divided by a pneumatically controlled splitter and any desired split ratio between traps and detector can be obtained. Moreover, a second pneumatic control allows instantaneous change-over to a different split ratio, thus minimizing loss of material during collection.The effluent containing the compounds of interest is passed through a multiple manifold and collected in coiled glass capillary traps. To ensure maximum trapping efficiency even for very small amounts of material, the inner walls of the capillary traps are wetted with a suitable solvent, which gives a quantitative recovery of micro-and nanogram amounts of material.After repetitive sampling, sufficient amounts of material can be obtained for NMR spectroscopy and possibilities exist to enrich tracecomponentswith theaidof adoublecolumnsystem. Two examples of such applications are given, employing mixtures of both synthetic and natural origin.

Collection of gas chromatographic fractions for NMR analysis

“…Before collecting a fraction, the capillaries were blackflushed with dry nitrogen. As described by Roeraade and Enzell [7], a thin film of solvent was then deposited on the wall of the trap at room temperature by injecting a few FI of solvent on the capillary column and collecting it in the trap. Copper coils were then immersed in their cold baths.…”

Instrumental Aspects of Gas Chromatography

“…Ideally, an effluent splitter should provide a fixed split ratio that is independent of flow rate, temperature and sample volatility. Effluent splitters for columns have been fabricated from glass-lined stainless steel [226,230,231], platinum/iridium microtubing [232,233], glass capillary tubing [234][235][236] and zero-dead volume metal tees [237]. For packed columns, T-splitters with fixed or valve-adjustable split ratios are generally used [227][228][229].…”

“…It should also minimize extracolumn band broadening, be chemically inert, and for convenience, provide some mechanism for adjusting the split ratio over a reasonable range, e.g., 1:1 to 1:100, and be easy to clean [226]. [230,233,235]. Dead volume effects are not usually a problem at packed column flow rates, although changes in the split ratio with temperature and the constancy of the split ratio with samples of different volatility may be.…”

Aspects of High-Resolution Gas Chromatography as Applied to the Analysis of Hydrocarbon Fuels and Other Complex Organic Mixtures. Volume 1

“…There is renewed interest in high-efficiency preparative collection techniques [160] and some progress is being made in this area. There has also been some preparative work conducted with glass OTCs where many sample injections are made, but only a select fraction, or group of compounds, is repetitively collected for subsequent analysis [161].…”