Effect of organic modifiers on retention and enantiomeric separations by capillary electrophoresis with human serum albumin as a chiral selector in solution

We have investigated the effect of methanol, ethanol, 1-propanol, 2-propanol and acetonitrile on the retention and enantiomeric separations of benzoin and propiomazine by capillary electrophoresis, using human serum albumin as a chiral selector. The effects of these modifiers on mobilities of analytes are rather difficult to interpret. Calculation of capacity factors reveals the underlying analyte-protein interactions; pitfalls in making such calculations are pointed out. In the case of benzoin and propiomazine binding to human serum albumin, capacity factors were observed to always decrease upon addition of organic modifiers, although the effects of 1- and 2-propanol suggest a possible specific interaction or modification of the protein conformation.