Identification
Shake 50mLof Oral Solution with 25mLof chloroform for 5minutes.Filter the chloroform extract through a pledget of cotton and a layer of anhydrous sodium sulfate,and evaporate on a warm water bath with the aid of a current of air to about 3mL.Continue the evaporation to dryness at room temperature.Wash the residue with two 10-mLportions of hot solvent hexane,decanting the solvent and discarding it each time.Digest the residue with 25mLof warm dehydrated alcohol for 15minutes.Filter the mixture,and evaporate the filtrate to about 3mL.Add solvent hexane until the mixture becomes slightly cloudy,and chill in a freezer to promote the formation of crystals.Collect the crystals,and dry at 60

for 1hour:the crystals meet the requirements for
Identificationtest
Aunder
Prednisone.
Assay
Mobile phase
Dissolve 1.36g of monobasic potassium phosphate in 600mLof water,add 400mLof methanol,pass through a 0.2-µm membrane filter,and degas.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Standard preparation
Using an accurately weighed quantity of
USP Prednisone RS,prepare a solution in alcohol containing 1mg per mL.Dilute 4volumes of this solution quantitatively with 96volumes of water to obtain a
Standard preparationhaving a known concentration of about 40µg per mL.
Assay preparation
Transfer an accurately measured volume of Oral Solution,equivalent to about 10mg of prednisone,to a 250-mLvolumetric flask.Dilute with water to 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 tailing factor for the analyte peak 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 by means of a sampling valve,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of prednisone (C
21H
26O
5)in each mLof the Oral Solution taken by the formula:
(0.25C/V)(rU/rS),
in which
Cis the concentration,in µg per mL,of
USP Prednisone RSin the
Standard preparation;Vis the volume,in mL,of Oral Solution taken;and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.