Chiral separations with coated and uncoated capillaries.

Chiral resolution depends on the time the two enantiomers have for active migration within the capillary. Consequently, the magnitude of the electroosmotic flow (EOF) has a paramount influence on resolution, especially for chiral acidic compounds (counterosmotic migration). In this case, when the mobility of the analytes relative to that of the EOF is known, a rule of thumb can be deduced: Coated capillaries with suppressed EOF should be used when the effective mobility of the analyte is less than 50% of that of the EOF. Uncoated capillaries give better resolution when the effective mobility of the analyte is higher than 50% of that of the EOF because of the longer effective migration distance. The efficiencies achieved are mainly a function of the time the analytes spend in the capillary when solute-wall interactions can be neglected.