Stationary phases general requirements

Enantiomer separation by hydrogen-bonding stationary phases generally requires substrate derivatization. Hence versatile derivatization strategies have been devised124. In some cases, enantiomer separation on Chirasil-Val may be carried out without prior derivatization, e.g., for alcohols and bifunctional carbonyl compounds145. A survey on compound classes which have been separated into enantiomers is available128. 

Enantiomer separation by hydrogen-bonding stationary phases generally requires substrate deriva-tization. 

The use of ionisation techniques such as El and Cl for TLC stationary phases has generally been limited to relatively nonpolar and thermally stable molecules. Polar involatile compounds, separated on silica gel, generally strongly adsorb on to the matrix, and decompose when heat is applied for volatilisation [817]. Use of less-adsorbent phases, such as polyamide, is particularly useful for TLC-EIMS work, because the analytes are not as strongly adsorbed to this phase and do not require high probe temperatures [818,819]. For compounds that are not suitable candidates for TLC-EIMS, FAB can be employed. Chemical ionisation, although suitable for TLC-MS, appears to have been little used. 

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