Test solution— Transfer a quantity of Oral Solution,equivalent to about 5mg of dexamethasone,to a 50-mLseparator,add 10mLof water,and extract with two 20-mLportions of chloroform.Filter the lower layers through chloroform-saturated cotton into a 50-mLconical flask,and evaporate to dryness.Dissolve the residue in 10mLof chloroform.

Developing solvent system: a mixture of methylene chloride and methanol (180:16).

Procedure— Visualize the spots,using a 1in 5solution of p-toluenesulfonic acid in a mixture of alcohol and propylene glycol (9:1)followed by heat.

Add the following:

For Oral Solution Packaged In Single-Unit Containers: meets the requirements.USP28

Add the following:

For Oral Solution Packaged In Multiple-Unit Containers: meets the requirements.USP28

Mobile phase— Prepare a filtered and degassed mixture of methanol,water,and glacial acetic acid (55:43:2).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluting solution— Prepare a mixture of methanol and water (1:1).

Standard preparation— Dissolve an accurately weighed quantity of USP Dexamethasone RSin Diluting solution,and dilute quantitatively,and stepwise if necessary,with Diluting solutionto obtain a solution having a known concentration of about 0.04mg per mL.

Assay preparation— Transfer an accurately measured volume of Oral Solution,equivalent to about 4mg of dexamethasone,to a 100-mLvolumetric flask,dilute with Diluting solutionto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 2000theoretical plates,the tailing factor is not more than 2.0,and the relative standard deviation for replicate injections is not more than 2.0%.

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 per mL,of dexamethasone (C22H29FO5)in the portion of Oral Solution taken by the formula: in which Lis the labeled quantity,in mg per mL,of dexamethasone in the Oral Solution;Dis the concentration,in mg per mL,of dexamethasone in the Assay preparationon the basis of the labeled quantity and the extent of dilution;Cis the concentration,in mg per mL,of USP Dexamethasone RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.