Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Methanol-acetonitrile solution— Prepare a solution by mixing equal volumes of methanol and acetonitrile.

Standard preparation— Dissolve an accurately weighed quantity of USP Prednisolone Acetate RSin Methanol-acetonitrile solution,and dilute quantitatively,and stepwise if necessary,with Methanol-acetonitrile solutionto obtain a solution having a known concentration of about 0.1mg per mL.

Assay preparation— Transfer an accurately measured volume of Injectable Suspension,equivalent to about 50mg of prednisolone acetate,to a 50-mLvolumetric flask,add Methanol-acetonitrile solutionto volume,and mix.Pipet 5mLof this solution into a second 50-mLvolumetric flask,dilute with Methanol-acetonitrile solutionto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation,and record the peak response as directed for Procedure:the capacity factor,k¢,is not less than 3.0,and the relative standard deviation for replicate injections is not more than 3.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C23H30O6in each mLof the Injectable Suspension taken by the formula: in which Cis the concentration,in mg per mL,of USP Prednisolone Acetate RSin the Standard preparation,Vis the volume,in mL,of Injectable Suspension taken,and rUand rSare the peak responses for prednisolone acetate obtained from the Assay preparationand the Standard preparation,respectively.