Identification—
Place a quantity of finely powdered Tablets, equivalent to about 10 mg of ethynodiol diacetate, in a stoppered, 15-mL centrifuge tube. Add 10 mL of acetonitrile, insert the stopper in the tube, and mix by shaking and inversion for about 2 minutes. Centrifuge at about 1200 rpm for 10 minutes, and decant the supernatant through filter paper into a suitable container. Evaporate a 5-mL aliquot of the filtrate on a steam bath with the aid of a stream of nitrogen, and dissolve the residue in 1 mL of chloroform. Apply 5 µL of the solution under test, 5 µL of a Standard solution of
USP Ethynodiol Diacetate RS in chloroform containing 5 mg per mL, and 5 µL of a Standard solution of
USP Mestranol RS in chloroform containing 0.5 mg per mL at points about 3 cm from one end of a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Place the plate in a developing chamber containing a mixture of 30 volumes of ethyl acetate and 70 volumes of cyclohexane to a depth of 2 cm, the developing chamber previously having been equilibrated with the solvent mixture as described under
Thin-layer Chromatography 621. Remove the plate when the solvent moves to about 15 cm above the initial spots, allow it to air-dry at room temperature, spray it with a 1 in 2 solution of sulfuric acid in water, and heat it at 80
for 10 minutes: the ethynodiol diacetate spots appear yellowish tan and the mestranol spots appear pink when viewed under white light. The ethynodiol diacetate and mestranol spots from the solution under test have the same relative positions on the plate as the spots from the respective Standard solutions: the
RF value of ethynodiol diacetate in this system is about 0.8, and the
RF value of mestranol in this system is about 0.6.
Uniformity of dosage units 905:
meet the requirements for
Content Uniformity with respect to ethynodiol diacetate and to mestranol.
Procedure for content uniformity—
Proceed as directed in the
Assay, except to reduce by half the concentrations in the
Standard preparation and the
Assay and to inject twice the volume into the chromatograph.
Assay—
Mobile phase—
Prepare a filtered and degassed mixture of methanol, water, and tetrahydrofuran (63:30:7), making adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve accurately weighed quantities of
USP Ethynodiol Diacetate RS and
USP Mestranol RS in a mixture of methanol and water (4:1) to obtain a solution having a known concentration of about 0.2 mg of ethynodiol diacetate per mL and 0.02 mg of mestranol per mL.
Assay preparation—
Transfer 10 Tablets to a glass-stoppered flask, and pipet a sufficient volume of a mixture of methanol and water (4:1) into the flask to obtain a solution having final concentration of approximately 0.2 mg of ethynodiol diacetate per mL and 0.02 mg of mestranol per mL. Agitate vigorously until the tablets are completely disintegrated. Shake vigorously by mechanical means for 30 minutes. Allow the solids to settle for 10 minutes, and filter the solution through a 0.5-µm filter.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 204-nm detector and a 4.6-mm × 25-cm column that contains packing L13. The flow rate is approximately 1.2 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed under
Procedure: the relative retention times are about 0.6 for mestranol and 1.0 for ethynodiol diacetate. The mestranol is baseline separated from the ethynodiol diacetate peak, and the resolution,
R, is not less than 4.0 between these two peaks. The relative standard deviation for replicate injections is not more than 2.0% for each analyte.
Procedure—
Separately inject equal volumes (about 25 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of ethynodiol diacetate (C
24H
32O
4) and mestranol (C
21H
26O
2) per Tablet taken by the formula:
0.1CV(rU / rS),
in which
C is the concentration, in mg per mL, of the appropriate USP Reference Standard in the
Standard preparation,
V is the volume, in mL, of the methanol-water solvent added to obtain the
Assay preparation, and
rU and
rS are the peak responses of the corresponding analyte obtained from the
Assay preparation and the
Standard preparation, respectively.
