SEPARATION OF PHARMACEUTICALLY IMPORTANT ESTROGENS BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY

Baseline separation of ten estrogens of the type found in conjugated e strogens tablets from pregnant mares' urine were separated by micellar electrokinetic chromatography with a 20 mM sodium borate-sodium phosp hate buffer (pH 8) containing either 75 mM sodium cholate and 15 mM be ta-cyclodextrin or 50 mM sodium dodecyl sulfate and 20 mM gamma-cyclod extrin. The system containing sodium cholate was used to identify estr ogens in a pharmaceutical tablet formulation of conjugated estrogens a nd to determine the amounts and ratio of sodium equilin sulfate to sod ium estrone sulfate to confirm tablet conformity with regulatory requi rements. Baseline separation of the seven ethynyl steroids registered as oral contraceptives in the USA was obtained with the system 20 mM s odium borate-sodium phosphate buffer (pH 8) containing 50 mM sodium ch olate and 10% (v/v) methanol. Factors that affect selectivity and repr oducibility of the above separation systems are discussed.