Note: Trifluoroacetic acid and triethylamine are typical retainers for the separation of acidic and basic compounds, respectively, where the stationary phase typically is the organic phase. The retainer determines the analyte concentration in the stationary phase. NH₄OH and HCl are commonly used as the eluter for the separation of acidic and basic compounds, respectively. The eluter always stays in the aqueous mobile phase to serve as a counter ion. pH-zone-refining CCC can also be performed using the organic phase as the mobile phase (normal displacement mode). In this case, the retainer becomes the eluter to elute the analytes, and the eluter becomes the retainer to retain the analytes in the aqueous stationary phase.