Hydrophobic basic compounds with more than one basic group are preferably analyzed on the anion-exchange Primesep columns (Primesep D
). Cation-exchange columns (Primesep 100
) provide very strong, sometimes irreversible retention due to both RP and IE combined interactions. An exception is the Primesep C
column, which at a low pH (<3.0) has a significantly reduced charge stationary phase. This column, especially the shorter version, can be used for hydrophobic bases with more than one basic group. Anion exchange columns decrease retention significantly because of the repulsion phenomena of the positively charged column surface as well as the positive charge of the analyte itself. Good peak symmetry and high efficiency is typical, even for very difficult basic compounds.