A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Test solution: 10 mg per mL, in chloroform.

Test solution: methanol.

Standard solution: methanol.

Application volume: 10 µL.

Eluant: a mixture of toluene and isopropyl alcohol (90:10), in a nonequilibrated chamber.

Visualization: 1.

Mobile phase— Prepare a filtered and degassed mixture of methanol and water (60:40). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Dissolve Prednisone in Mobile phase, with the aid of sonication, to obtain a solution containing about 1 mg per mL.

Standard preparation— Transfer about 5 mg of USP Flurandrenolide RS, accurately weighed, to a 10-mL volumetric flask, add 2.0 mL of Internal standard solution, dilute with Mobile phase to volume, sonicate to aid solution, and mix to obtain a solution having a known concentration of about 0.5 mg of USP Flurandrenolide RS per mL.

Assay preparation— Transfer about 5 mg of Flurandrenolide, accurately weighed, to a 10-mL volumetric flask, add 2.0 mL of Internal standard solution, dilute with Mobile phase to volume, sonicate to aid solution, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 240-nm detector and a 4-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the order of elution is prednisone followed by flurandrenolide, the resolution; R, between the analyte and internal standard is not less than 2.0; and the relative standard deviation for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. The relative retention times are about 0.5 for prednisone and 1.0 for flurandrenolide. Calculate the quantity, in mg, of C24H33FO6 in the portion of Flurandrenolide taken by the formula: in which C is the concentration, in mg per mL, of USP Flurandrenolide RS in the Standard preparation; and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.