A: Injection meets the requirements for Identification testAunderDigoxin Elixir(Oral Solution,Official June 1,2005).

B:Chloramine T–trichloroacetic acid reagent,Spotting solvent,and Standard solution— Proceed as directed forIdentification testBunderDigoxin Elixir (Oral Solution,Official June 1,2005).

Test solution— Pipet a volume of Injection,equivalent to 0.5mg of digoxin,into a separator,and add 5mLof water.Extract with three 10-mLportions of chloroform,combining the extracts in a conical flask.Evaporate the combined chloroform extracts on a steam bath with the aid of a current of air to dryness.(If traces of water or propylene glycol remain,dry the flask in vacuum at 100for 30minutes.)Dissolve the residue in 2mLofSpotting solvent.

Procedure— Proceed as directed forProcedure in the test forRelated glycosides underDigoxin,except to omit the use of theGitoxin standard solution.Examine the plate under long-wavelength UVlight:theRFvalue of the principal spot in the chromatogram of theTest solution corresponds to that of theStandard solution.

Mobile phase— Proceed as directed in theAssay underDigoxin.

Standard preparation— Dissolve an accurately weighed quantity of USP Digoxin RSin diluted alcohol,and dilute quantitatively with diluted alcohol to obtain a solution having a known concentration of about 250µg per mL.Use a sonic bath to aid dissolution.If necessary,dilute quantitatively to match,approximately,the concentration of the Injection.

Chromatographic systemand System suitability preparation— Proceed as directed in theAssay underDigoxin.

Procedure— Separately inject equal volumes (about 10µL)of theStandard preparation and Injection into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in µg,of C41H64O14in each mLof the Injection taken by the formula: in whichCis the concentration,in µg per mL,of USP Digoxin RSin theStandard preparation;and rUandrSare the responses for the digoxin peaks obtained from the Injection and theStandard preparation,respectively.