Method development in pharmaceutical analysis employing capillary electrochromatography

Capillary electrochromatography (CEC) has been employed to explore method development for a series of structurally related polar neutral compounds of pharmaceutical relevance. Capillaries with dimensions of 75 mu m ID x 25 cm length (34.5 cm total) were packed with Spherisorb ODS-1, Hypersil phenyl, and Hypersil MOS (all 3 mu m particles) and were compared in the reversed-phase mode in order to determine which phase provided the best initial performance and thus serve as the phase of choice for additional method development experiments. The various separation parameters examined for their effect on efficiency, k', resolution, and linear velocity included percent and type of organic modifier, buffer concentration, voltage, and temperature. All separations were conducted with an acidic mobile phase (aqueous mobile phase component, pH 3.0). The separation efficiencies obtained were on the order of 200 000-260 000 plates/m, which equates to reduced plate heights of 1.22 for columns packed with Spherisorb, ODS-1. Repeatable column-to-column separation performance was demonstrated.