Mobile phase, pH 6.0 Buffer solution, Diluent, and Chromatographic system— Proceed as directed in the Assay under Dexamethasone Acetate.

Standard preparation— Dissolve an accurately weighed quantity of USP Dexamethasone Acetate RS in Diluent to obtain a solution having a known concentration of about 0.09 mg per mL.

Assay preparation— Transfer an accurately measured volume of well-shaken Injectable Suspension, equivalent to about 40 mg of dexamethasone, to a 100-mL volumetric flask. Add 75 mL of Diluent, and sonicate until a clear solution is obtained. Dilute with Diluent to volume, and mix. Transfer 10.0 mL of this solution to a 50-mL volumetric flask, dilute with Diluent to volume, and mix.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation (before and after injections of the Assay 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 dexamethasone (C22H29FO5) in each mL of the Injectable Suspension taken by the formula: in which 392.47 and 434.51 are the molecular weights of dexamethasone and anhydrous dexamethasone acetate, respectively; C is the concentration, in mg per mL, of USP Dexamethasone Acetate RS in the Standard preparation; V is the volume, in mL, of Injectable Suspension taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.