Capillary columns for enantiomer separation by MACHEREY-NAGEL GmbH & Co. KG

Enantiodifferentiation is an important aspect in the activity of biological systems: enantiomers of chiral odour and flavour components as well as pharmaceuticals can possess very different properties. For this reason, separation and analysis of enantiomers gains increasing importance. Especially capillary gas chromatography with chiral stationary phases is the method of choice, because it features high resolution and sensitivity combined with simple detection and high precision. Reproducibility is excellent, the amount of substance required for the analysis is low.

The most important chiral phases can be assigned to two types:
- modified cyclodextrins (LIPODEX®, HYDRODEX)
- chiral polysiloxanes of the diamide type (e.g. L-CHIRASIL-VAL)

Enantiomer separation based on chemically modified cyclodextrins 
Cyclodextrins are cyclic oligosaccharides consisting of six (α-cyclodextrin), seven (ß-cyclodextrin) or eight (γ-cyclodextrin) glucose units bonded through a-1,4-linkages. By complete alkylation or by partial alkylation and (regioselective) acylation of these cyclodextrins one can synthesise a number of different derivatives with varying enantioselectivity, which have been intensively studied and which are well suited as chiral stationary phases for gas chromatographic enantiomer analyses.

One important advantage of these phases is that many compounds can be analysed without derivatisation.

For coating fused silica capillaries, cyclodextrins are either used as pure, undiluted phases (FS-LIPODEX®) or dissolved in polysiloxane (FS-HYDRODEX).