A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Test solution: 10 mg per mL, in dioxane.

Solution A— Prepare a filtered and degassed mixture of water and acetonitrile (77:23).

Solution B— Prepare a filtered and degassed mixture of water and acetonitrile (60:40).

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent: a mixture of water and acetonitrile (1:1).

Standard solution— Dissolve an accurately weighed quantity of USP Prednisolone RS in Diluent, and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 0.01 mg per mL.

System suitability solution— Dissolve an accurately weighed quantity of USP Prednisolone RS and hydrocortisone in Diluent to obtain a solution having a known concentration of about 1 mg per mL and 0.06 mg per mL, respectively.

Test solution— Transfer about 25 mg of Prednisolone, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with Diluent to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 30-cm column that contains 5-µm packing L1. The flow rate is about 1.5 mL per minute. The column temperature is maintained at 40. The chromatograph is programmed as follows. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times for prednisolone and hydrocortisone are about 1.0 and 1.06, respectively; and the height of the smallest peak is not less than 2 times the height of the valley between the prednisolone and hydrocortisone peaks. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 5.0% for the prednisolone peak.

Mobile phase— Prepare a solution containing a mixture of butyl chloride, water-saturated butyl chloride, tetrahydrofuran, methanol, and glacial acetic acid (95:95:14:7:6). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Prepare a solution of betamethasone in tetrahydrofuran containing 5 mg per mL. Dilute this solution with water-saturated chloroform, and mix to obtain a solution having a final concentration of 0.5 mg per mL.

Standard preparation— Transfer about 10 mg of USP Prednisolone RS, accurately weighed, to a 100-mL volumetric flask, and dissolve in 5.0 mL of methanol. Add 20.0 mL of Internal standard solution, and mix. Dilute with water-saturated chloroform to 100.0 mL, and mix.

Assay preparation— Transfer about 10 mg of Prednisolone, accurately weighed, to a 100-mL volumetric flask, and dissolve in 5.0 mL of methanol. Add 20.0 mL of Internal standard solution, and mix. Dilute with water-saturated chloroform to 100.0 mL, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains packing L3. The flow rate is about 1 mL per minute. Chromatograph four replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.7 for betamethasone and 1.0 for prednisolone; the resolution, R, between prednisolone and betamethasone is not less than 3.5; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 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 C21H28O5 in the portion of Prednisolone taken by the formula: in which C is the concentration, in µg per mL, of USP Prednisolone RS in the Standard preparation; and RU and RS are the peak response ratios of prednisolone to the internal standard obtained from the Assay preparation and the Standard preparation, respectively.