A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Test solution: 10 mg per mL, in dioxane.

Mobile phase— Prepare a filtered and degassed mixture of isooctane, butyl chloride and methanol (49:49:2). Make adjustments if necessary (see System Suitability under Chromatography 621).

Test solution— Transfer about 10 mg of Prednisolone Acetate, accurately weighed, to a suitable container, dissolve in 10 mL of chloroform, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 6.0-mm × 4.0-cm column that contains packing L3. The flow rate is about 3 mL per minute. Chromatograph the Test solution, and record the peak responses as directed for Procedure: the column efficiency is not less than 800 theoretical plates; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject a volume (about 10 µL) of the Test solution into the chromatograph, record the chromatogram, and measure all the peak responses. Calculate the percentage of each impurity in the portion of Prednisolone Acetate taken by the formula: in which ri is the peak response for each impurity; and rs is the sum of the responses for all the peaks: not more than 1.0% of any individual impurity is found; and not more than 2.0% of total impurities is found.

Mobile phase— Prepare a solution containing a mixture of n-butyl chloride, water-saturated n-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 10 mg per mL. Dilute this solution with water-saturated chloroform, and mix to obtain a solution having a final concentration of about 1 mg of betamethasone per mL.

Standard preparation— Transfer about 10 mg of USP Prednisolone Acetate RS, accurately weighed, to a 100-mL volumetric flask; add 20.0 mL of Internal standard solution; and dissolve, using sonication if necessary. Dilute with water-saturated chloroform to volume, and mix. Dilute 5.0 mL of the solution so obtained with water-saturated chloroform to 20.0 mL to obtain a solution having a known concentration of about 25 µg of USP Prednisolone Acetate RS per mL.

Assay preparation— Transfer about 10 mg of Prednisolone Acetate, accurately weighed, to a 100-mL volumetric flask; add 20.0 mL of Internal standard solution; and dissolve, using sonication if necessary. Dilute with water-saturated chloroform to volume, and mix. Dilute 5.0 mL of the solution so obtained with water-saturated chloroform to 20.0 mL.

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 the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 1.6 for betamethasone and 1.0 for prednisolone acetate; the resolution, R, between prednisolone acetate and betamethasone is not less than 3.0; 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 C23H30O6 in the portion of Prednisolone Acetate taken by the formula: in which C is the concentration, in µg per mL, of USP Prednisolone Acetate RS in the Standard preparation; and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.