A: Thin-Layer Chromatographic Identification Test 201—

B: The retention times of the major peaks in the chromatogram of the Assay preparation corresponds to those in the chromatogram of the Standard preparation, as obtained in the Assay.

test 1—

test 2— If the product complies with this test, the labeling indicates that it meets USP Dissolution Test 2.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and 20 mM potassium phosphate buffer, pH 6.0 (50:50). Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent— Prepare a mixture of acetonitrile and water (50:50).

Desogestrel standard stock solution— Dissolve an accurately weighed quantity of USP Desogestrel RS in methanol, and dilute quantitatively, and stepwise if necessary, with methanol to obtain a solution having a known concentration of about 0.3 mg per mL.

Ethinyl estradiol standard stock solution— Dissolve an accurately weighed quantity of USP Ethinyl Estradiol RS in methanol, and dilute quantitatively, and stepwise if necessary, with methanol to obtain a solution having a known concentration of about 0.3 mg per mL.

Standard preparation— Dilute appropriate aliquots of Desogestrel standard stock solution and Ethinyl estradiol standard stock solution with Diluent to obtain a solution having a known concentration of about 0.6 µg per mL and 0.12 µg per mL of USP Desogestrel RS and USP Ethinyl Estradiol RS, respectively.

Assay preparation— Transfer 20 Tablets into a 200-mL volumetric flask. Add about 120 mL of Diluent, and shake for about 30 minutes. Dilute with Diluent to volume, and mix. Centrifuge a portion of the sample, and transfer an accurately measured volume to a 50-mL volumetric flask to obtain a final concentration of about 0.6 µg per mL of desogestrel. Dilute with Diluent to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 210-nm detector (for desogestrel analysis); a spectrofluorometric detector (for ethinyl estradiol analysis) with an excitation wavelength of 285 nm and an emission wavelength of 310 nm; a 4.6-mm × 15-cm column that contains packing L11; and a 4.6-mm × 12.5-mm guard column that also contains packing L11. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.2 for ethinyl estradiol and 1.0 for desogestrel; the tailing factor for both analytes is not more than 2.0; and the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 200 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 percentage of desogestrel (C22H30O) and ethinyl estradiol (C20H24O2) in the portion of Tablets taken by the formula: in which CS is the concentration, in mg per mL, of USP Desogestrel RS or USP Ethinyl Estradiol RS in the Standard preparation;CU is the concentration, in mg per mL, of desogestrel or ethinyl estradiol in the Assay preparation based on the label claim; and rU and rS are the peak responses for desogestrel or ethinyl estradiol obtained from the Assay preparation and the Standard preparation, respectively.