The configurational integrity of the enantiomers during the GC process of separation is essential for a correct enantiomer analysis. When enantiomers invert the configuration (or conformation) during separation, transient elution profiles are obtained that are characterized by plateau formation between the terminal peaks of the enantiomers. The barrier of enan-tiomerization (AG*) can be determined by dynamic GC via peak form analysis of interconversion profiles and the comparison of experimental and simulated chromatograms (cf. Figure 2). Only minute amounts of the easily available racemic compound are required. If enantiomerization is fast within the chromatographic timescale, peak coalescence (third kind) occurs (cf. Figure 2 at 130°C).

Another on-column method for determining interconversion kinetics is based on the 'stopped-flow' technique. In the first part of the column enantiomers are quantitatively separated. Afterwards, the flow is stopped and the column is heated, whereby enan-tiomerization in the separated fractions commences. After cooling, the flow is restored and the enan-tiomerized fractions are separated in the second part of the column. From the reaction time and enan-tiomeric compositions the rate constant can be calculated. Using a combination of three columns, i.e. a separation column, an empty reactor column and another separation column, connected via switching valves for peak-cutting, enantiomerization can be carried out in the gas phase and in the absence of the CSP in the reactor column (enantioselective multidimensional stopped-flow GC).

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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