Medium: 0.01 N hydrochloric acid; 500 mL.

Apparatus 2: 75 rpm.

Time: 30 minutes.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and water (45:55). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Transfer about 25 mg of USP Fludrocortisone Acetate RS, accurately weighed, to a 1000-mL volumetric flask. Add 50 mL of acetonitrile, and sonicate for 5 minutes to dissolve. Dilute with 0.01 N hydrochloric acid to volume to obtain a known concentration of fludrocortisone acetate similar to that expected in the solution under test.

Chromatographic system (see Chromatography 621)—The chromatograph is equipped with a 245-nm detector and a 4.6-mm × 15-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the column efficiency is not less than 1000 theoretical plates, the tailing factor is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 100 µL) of a filtered portion of the solution under test and the Standard solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity of C23H31FO6 dissolved based on the peak responses obtained from the solution under test and the Standard solution.

Tolerances— Not less than 80% (Q) of the labeled amount of C23H31FO6 is dissolved in 30 minutes.

Procedure for content uniformity—

Mobile solvent— Prepare as directed in the Assay.

Internal standard solution— Prepare a solution of USP Norethindrone RS in acetonitrile having a concentration of about 10 µg per mL.

Standard preparation— Dissolve a suitable quantity of USP Fludrocortisone Acetate RS, accurately weighed, in Internal standard solution to obtain a solution having a known concentration of about 0.20 mg per mL. Add 5.0 mL of this solution to 10.0 mL of water contained in a low-actinic 50-mL volumetric flask. Dilute with Internal standard solution to volume to obtain a solution having a known concentration of about 20 µg of fludrocortisone acetate per mL.

Test preparation— Add 1.0 mL of water to 1 Tablet in a 10-mL centrifuge tube, and mix on a vortex-type mixer for 1 minute or until disintegration is complete. Add 4.0 mL of Internal standard solution, mix on a vortex-type mixer for 1 minute, then shake by mechanical means for not less than 40 minutes. Centrifuge at 3600 rpm for 20 minutes, or until a clear supernatant is obtained. Use the clear supernatant.

Procedure— Proceed as directed for Procedure in the Assay. Calculate the quantity, in mg, of C23H31FO6 in the Tablet taken by the formula: in which C, RU, and RS are as defined in the Assay; T is the labeled quantity, in mg, of fludrocortisone acetate in the Tablet; and D is the concentration, in µg per mL, of fludrocortisone acetate in the Test preparation, based on the labeled quantity per Tablet and the extent of dilution.

Mobile solvent— Prepare a suitable, degassed acetonitrile solution, 40% to 45% (v/v), such that the resolution factor, R, between fludrocortisone acetate and the internal standard is not less than 2.5.

Internal standard solution— Prepare a solution of USP Norethindrone RS in acetonitrile having a concentration of about 75 µg per mL.

Standard preparation— Dissolve a suitable quantity of USP Fludrocortisone Acetate RS, accurately weighed, in Internal standard solution to obtain a solution having a known concentration of about 0.50 mg per mL. Pipet 5 mL of this solution into a 25-mL volumetric flask containing 5.0 mL of water. Dilute with Internal standard solution to volume to obtain a solution having a known concentration of about 0.1 mg of fludrocortisone acetate per mL.

Assay preparation— Weigh and finely powder not fewer than 35 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 2.5 mg of fludrocortisone acetate, to a low-actinic, glass-stoppered, 50-mL centrifuge tube. Add 5.0 mL of water, and mix for 1 minute. Add 20.0 mL of Internal standard solution, mix by mechanical means for 40 minutes, then centrifuge for 15 minutes or until a clear supernatant is obtained. Use the clear supernatant.

Procedure— Introduce equal volumes (about 20 µL) of the Assay preparation and the Standard preparation into a high-pressure liquid chromatograph (see Chromatography 621) operated at room temperature, by means of a suitable microsyringe or sampling valve, adjusting the specimen size and other operating parameters such that the peak obtained with the Standard preparation is about 0.7 full scale. Typically, the apparatus is fitted with a 3.9-mm × 30-cm stainless steel column packed with packing L1, and equipped with an UV detector capable of monitoring absorption at 254 nm and a suitable recorder. In a suitable chromatogram, the coefficient of variation for five replicate injections of the Standard preparation is not more than 3.0% and the resolution factor, R, is not less than 2.5 between the two peaks. Measure the height of the peaks, at identical retention times, obtained with the Assay preparation and the Standard preparation, and calculate the quantity, in mg, of fludrocortisone acetate (C23H31FO6) in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Fludrocortisone Acetate RS in the Standard preparation; and RU and RS are the ratios of the peak heights of the fludrocortisone acetate peak to the internal standard peak from the Assay preparation and the Standard preparation, respectively.