A: Infrared Absorption 197M.

B: Ultraviolet Absorption 197U—

Test solution: 10 mg per mL, in dioxane.

Diluent— Prepare a mixture of water, tetrahydrofuran, acetonitrile, and acetic acid (47:25:25:3).

Mobile phase— Prepare a filtered and degassed mixture of water, tetrahydrofuran, and formic acid (745:255:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Dissolve an accurately weighed quantity of USP Methylprednisolone Hemisuccinate RS in Diluent to obtain a solution having a final concentration of about 0.02 mg per mL.

Test solution— Prepare a solution of Methylprednisolone Hemisuccinate in Diluent containing about 1 mg per mL. Shake or sonicate to aid in solubilization.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 20-cm column that contains 5-µm packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the column efficiency determined from the methylprednisolone hemisuccinate peak is not less than 5000; and the relative standard deviation for replicate injections is not more than 5.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure all of the peak areas. Calculate the percentage of each impurity in the portion of Methylprednisolone Hemisuccinate taken by the formula: in which CS is the concentration, in mg per mL, of USP Methylprednisolone Hemisuccinate RS in the Standard solution; CU is the concentration, in mg per mL, of Methylprednisolone Hemisuccinate in the Test solution; ri is the peak area for each impurity obtained from the Test solution; and rS is the peak area of methylprednisolone hemisuccinate obtained from the Standard solution: not more than 1.0% of any individual impurity is found, and not more than 2.0% of total impurities is found.

(Official January 1, 2007)

Internal standard solution— Dissolve USP Fluorometholone RS in tetrahydrofuran to obtain a solution containing about 6 mg per mL.

Mobile phase— Prepare a solution containing a mixture of butyl chloride, water-saturated butyl chloride, tetrahydrofuran, methanol, and glacial acetic acid (475:475:70:35:30).

Standard preparation— Transfer about 40 mg of USP Methylprednisolone Hemisuccinate RS, accurately weighed, to a 100-mL volumetric flask. Add 5.0 mL of Internal standard solution. Dilute with chloroform containing 3% glacial acetic acid to volume, and mix to dissolve the powder.

Assay preparation— Using about 40 mg of Methylprednisolone Hemisuccinate, accurately weighed, prepare as directed for Standard preparation.

Procedure— Using a suitable microsyringe or sampling valve, inject separately suitable portions, between 4 and 8 µL, of the Standard preparation and the Assay preparation into a suitable high-pressure liquid chromatograph (see Chromatography 621) of the general type equipped with a detector for monitoring UV absorption at about 254 nm, equipped with a suitable recorder, capable of providing column pressure up to about 1000 psi and fitted with a 4-mm × 30-cm stainless steel column that contains packing L3. In a suitable chromatogram, the resolution, R, between methylprednisolone hemisuccinate and the internal standard is not less than 2.0; and six replicate injections of the Standard preparation show a coefficient of variation of not more than 2.0%. Calculate the quantity, in mg, of C26H34O8 in the portion of Methylprednisolone Hemisuccinate taken by the formula: in which C is the concentration, in mg per mL, of USP Methylprednisolone Hemisuccinate RS in the Standard preparation; and RU and RS are the peak area ratios of methylprednisolone hemisuccinate to the internal standard obtained from the Assay preparation and the Standard preparation, respectively.