A: Infrared Absorption á197Mñ.

B: Ultraviolet Absorption á197Uñ—

Test solution: 10mg 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 Suitabilityunder Chromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of USP Methylprednisolone Hemisuccinate RSin Diluentto obtain a solution having a final concentration of about 0.02mg per mL.

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

Chromatographic system (see Chromatography á621ñ)—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 1.0mLper 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 20µL)of the Standard solutionand the Test solutioninto 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 CSis the concentration,in mg per mL,of USP Methylprednisolone Hemisuccinate RSin the Standard solution;CUis the concentration,in mg per mL,of Methylprednisolone Hemisuccinate in the Test solution;riis the peak area for each impurity obtained from the Test solution;and rSis 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.

Internal standard solution— Dissolve USP Fluorometholone RSin tetrahydrofuran to obtain a solution containing about 6mg 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 40mg of USP Methylprednisolone Hemisuccinate RS,accurately weighed,to a 100-mLvolumetric flask.Add 5.0mLof Internal standard solution.Dilute with chloroform containing 3%glacial acetic acid to volume,and mix to dissolve the powder.

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

Procedure— Using a suitable microsyringe or sampling valve,inject separately suitable portions,between 4and 8µL,of the Standard preparationand the Assay preparationinto a suitable high-pressure liquid chromatograph (see Chromatography á621ñ)of the general type equipped with a detector for monitoring UVabsorption at about 254nm,equipped with a suitable recorder,capable of providing column pressure up to about 1000psi 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 preparationshow a coefficient of variation of not more than 2.0%.Calculate the quantity,in mg,of C26H34O8in the portion of Methylprednisolone Hemisuccinate taken by the formula: in which Cis the concentration,in mg per mL,of USP Methylprednisolone Hemisuccinate RSin the Standard preparation;and RUand RSare the peak area ratios of methylprednisolone hemisuccinate to the internal standard obtained from the Assay preparationand the Standard preparation,respectively.