Retention Behavior of Highly Hydrophobic, Structurally Related Corticosteroids with SDS Based Microemulsion

Abstract The present work describes the retention behavior of structurally related corticosteroids separated with SDS based microemulsion. The analytes include cortisone acetate (CA), hydrocortisone (H), hydrocortisone acetate (HA), prednisolone (P), prednisolone acetate (PA), and prednisone (Ps), which are not easily separated by the conventional MEKC. Surfactants with linear and planar structures have been compared for the separation of these analytes. By fine tuning the parameters, the results revealed that complete baseline separation could be achieved with a microemulsion consisted of 0.8% (w/w) n-octane, 3.6% (w/w) SDS, 6.6% (w/w) 1-butanol, and 89% (w/w) phosphate buffer (40 mM, pH 8.0), under an applied voltage of +7 kV and a column dimension of 53 cm (effective length, 30 cm) × 75 μm id. Although the composition of the microemulsion has a high recognition property for these structurally related compounds, the high affinity of these analytes with the pseudostationary phase made the analysis time v...