Medium: 0.05% polysorbate 20; 600 mL.

Apparatus 2: 75 rpm.

Time: 20 minutes for Tablets labeled as containing 180 µg of C23H31NO3 and 35 µg of C20H24O2; 20 minutes for Tablets labeled as containing 215 µg of C23H31NO3 and 35 µg of C20H24O2; and 30 minutes for Tablets labeled as containing 250 µg of C23H31NO3 and 35 µg of C20H24O2.

Mobile phase— Prepare a degassed mixture of water and isopropyl alcohol (13:7). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Dissolve an accurately weighed quantity of USP Norgestimate RS and USP Ethinyl Estradiol RS in Medium, and dilute quantitatively, and stepwise if necessary, with Medium to obtain a solution having known concentrations similar to those expected in the Test solution. [note—A volume of methanol not exceeding 4% of the total volume of the Standard solution may be used to bring the standards into solution prior to dilution with Medium.]

Test solution— Use a filtered or centrifuged portion of the solution under test.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector (for norgestimate analysis), a spectrofluorometric detector (for ethinyl estradiol analysis) with an excitation wavelength of 234 nm and an emission wavelength of 304 nm, and a 4.6-mm × 25-cm column that contains packing L10. The flow rate is about 1.2 mL per minute. The column temperature is maintained at 40. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the retention times are about 7.5 minutes for ethinyl estradiol and 9.5 minutes for norgestimate; and the relative standard deviation for replicate injections is not more than 3.0% for the ethinyl estradiol and norgestimate peaks.

Procedure— Separately inject equal volumes (about 200 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of each drug substance dissolved by the formula: in which C is the concentration, in mg per mL, of the appropriate analyte in the Standard solution; and rU and rS are the peak responses obtained from the Test solution and the Standard solution, respectively.

Tolerances— Not less than 80% (Q) of the labeled amounts of C23H31NO3 and C20H24O2 are dissolved in 20 minutes for Tablets labeled as containing 180 µg of C23H31NO3 and 35 µg of C20H24O2, and for Tablets labeled as containing 215 µg of C23H31NO3 and 35 µg of C20H24O2. Not less than 80% (Q) of the labeled amounts of C23H31NO3 and C20H24O2 are dissolved in 30 minutes for Tablets labeled as containing 250 µg of C23H31NO3 and 35 µg of C20H24O2.

Mobile phase— Proceed as directed in the Assay.

Standard solution— Use the Standard preparation, prepared as directed in the Assay.

Test solution— Use the Assay preparation, prepared as directed in the Assay.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a detector capable of detecting at 230 nm and 254 nm, simultaneously, and a 4.6-mm × 5-cm column that contains 5-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard solution, and record the peak areas as directed for Procedure: the relative retention times are about 0.5 for ethinyl estradiol, 1.0 for (Z)-norgestimate, and 1.2 for (E)-norgestimate; the resolution, R, between (Z)-norgestimate and (E)-norgestimate is not less than 1.5; and the relative standard deviation for replicate injections of the ethinyl estradiol and norgestimate peaks is not more than 2.0%.

Procedure— Inject a volume (about 50 µL) of the Test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the percentage of the impurity having a relative retention time of about 0.6, relative to the (Z)-norgestimate peak, and detected at 230 nm in the portion of Tablets taken by the formula: in which 1.31 is the relative response factor of this impurity; ri is the peak response for the impurity; and rs is the sum of the peak responses for (E)-norgestimate and (Z)-norgestimate: not more than 7.5% is found. Calculate the percentage of any impurity having a relative retention time of about 0.2 or 0.4, relative to the (Z)-norgestimate peak, and detected at 254 nm in the portion of Tablets taken by the formula: in which 1.54 is the relative response factor of the impurity peaks; CZ and CE are the quantities, in mg, of (Z)-norgestimate and ethinyl estradiol, respectively, as determined in the Assay; ri is the peak response for each impurity; and rZ is the peak response for (Z)-norgestimate: the sum of the impurities having relative retention times of about 0.2 and 0.4 is not more than 4.0%.

Mobile phase— Prepare a degassed mixture of water, tetrahydrofuran, and methanol (13:5:2). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Dissolve an accurately weighed quantity of dibutyl phthalate in methanol to obtain a solution having a concentration of about 0.05 mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Norgestimate RS and USP Ethinyl Estradiol RS in Internal standard solution, and dilute quantitatively, and stepwise if necessary, with Internal standard solution to obtain a solution having a known concentration of about 7 µg per mL of ethinyl estradiol and a known concentration similar to that expected in the Assay preparation. Mix, and pass through a filter having a 0.45-µm porosity.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 0.175 mg of ethinyl estradiol, to a 50-mL glass centrifuge tube, and add two glass beads. Add 25.0 mL of Internal standard solution, insert the stopper, and mix on a vortex mixer for at least 15 minutes. Sonicate for at least 5 minutes to ensure complete dissolution of the drug substances, mix, and pass through a filter having a 0.45-µm porosity.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm × 5-cm column that contains 5-µm packing L1. The flow rate is about 2.1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.5 for ethinyl estradiol, 1.0 for (Z)-norgestimate, 1.2 for (E)-norgestimate and 1.5 for dibutyl phthalate; the resolution, R, between (Z)-norgestimate and (E)-norgestimate is not less than 1.5; and the relative standard deviation of the peak response ratio of ethinyl estradiol, (Z)-norgestimate, and (E)-norgestimate to dibutyl phthalate from replicate injections is not more than 2.0%.

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 ethinyl estradiol (C20H24O2) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Ethinyl Estradiol RS in the Standard preparation; and RU and RS are the ratios of the peak responses of ethinyl estradiol to dibutyl phthalate obtained from the Assay preparation and the Standard preparation, respectively. Calculate the quantity, in mg, of norgestimate (C23H31NO3) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Norgestimate RS in the Standard preparation; PA and PS are the corresponding (E) and (Z) fractions of USP Norgestimate RS; RUA and RSA are the ratios of the peak responses of (E)-norgestimate to dibutyl phthalate obtained from the Assay preparation and the Standard preparation, respectively; and RUS and RSS are the ratios of the peak responses of (Z)-norgestimate to dibutyl phthalate obtained from the Assay preparation and the Standard preparation, respectively.