Re-evaluation of strong cation-exchange high-performance liquid chromatography for the analysis of basic drugs

Strong cation-exchange (SCX) HPLC has been systematically evaluated for the chromatography of basic compounds using an eluent of 80% methanol containing ammonium formate (0.02 M) with the pH adjusted to 2.45 with trifluoroacetic acid. Contrary to common perception SCX-HPLC is capable of high efficiencies (> 60 000 plates/m) and good peak symmetries (A(s) typically < 1.2). Retention shows the expected dependency on the reciprocal of the eluent ammonium concentration and eluent pH. Other mechanisms of retention have also been demonstrated including partitioning and hydrogen bond interactions. Control of the separation selectivity is possible through systematic adjustment of the eluent parameters such as ionic strength, pH and methanol concentration. SCX-HPLC is shown to be a powerful separation procedure for the analysis of basic compounds.