Colorimetric determination of mestranol in combination with ethynodiol diacetate

Mestranol in combination with ethynodiol diacetate, an oral contraceptive formulation, is isolated from the sample on a partition chromatographic column prior to colorimetric determination. The color reaction which is specific for estrogens is formed by shaking an aliquot of the heptane eluate of mestranol with a 30% methanol-sulfuric acid solution. A collaborative study of the method gave results of 99.8% of added mestranol for the simulated mix and 100.7% of labelled mestranol for the commercial tablet. The method has been adopted as official first aciton.