The pH of the mobile phase was another critical factor affection
enatioselectivity. To investigate the effect of pH on the enantioseparation,
the pH of the mobile phase was varied from 4.0 to 7.0. Fig.
8 shows that the selectivity and retention of the two enantiomers
increased with the pH increasing to 6.0; further increase of the pH
tended to decrease the k and α. Moreover, higher pH would cause
the precipitation of exceeding Cu2+. In this case, pH=6.0 was a suitable
pH value.