Capillary electrochromatography of tricyclic antidepressants on strong cation exchangers with different pore sizes

Four cation-exchange materials, possessing propanesulfonic acid ligands, for use in capillary electrochromatography were prepared from different commercially available 5-μm bare-silica particles ranging from 80 to 800 Å in pore size. The performance of the materials was investigated at different compositions of the mobile phase (pH, ionic strength, and acetonitrile content) using tricyclic antidepressants and related quaternary ammonium analogues as test analytes. The wide-pore materials promoted pore flow, but this had no positive influence on the performance. The small-pore (highest surface area) particles gave, as could be expected, the best selectivity.