A: The UVabsorption spectrum of the solution employed for measurement of absorbance in the Assayexhibits maxima and minima at the same wavelengths as that of a similar solution of USP Flunixin Meglumine RS,concomitantly measured.

B: Grind a quantity of Granules,equivalent to about 25mg of flunixin,and transfer the powder to a 50-mLcentrifuge tube.Add 20mLof acetate buffer,prepared by dissolving 4.1g of anhydrous sodium acetate in 500mLof water,adding 2.9mLof glacial acetic acid,and diluting with water to 1000mL.Rotate the tube for 10minutes.Extract with 25mLof ethyl acetate,and use the upper phase as the test solution.Separately apply 10µLof the test solution and 10µLof a Standard solution of USP Flunixin Meglumine RSin methanol containing 1.5mg per mLto a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry,and develop the chromatograms in a solvent system consisting of a mixture of toluene,ethyl acetate,glacial acetic acid,and water (65:30:10:1)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow the spots to air-dry.Examine the plate under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

Medium: 0.1Nhydrochloric acid;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Transfer a quantity of Granules,equivalent to about 12.5mg of flunixin,to the dissolution flask.Determine the amount of flunixin (C14H11F3N2O2)dissolved from UVabsorbances at the wavelength of maximum absorbance at about 252nm on filtered portions of solution under test in comparison with a Standard solution having a known concentration of about 23.6µg per mLof USP Flunixin Meglumine RSin the same Medium.Each µg of flunixin meglumine is equivalent to 0.6028µg of flunixin.

Tolerances— Not less than 75%(Q)of the labeled amount of flunixin (C14H11F3N2O2)is dissolved in 30minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Flunixin Meglumine RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 0.82mg per mL.Transfer 4.0mLof this solution to a 100-mLvolumetric flask,dilute with 0.1Nsodium hydroxide to volume,and mix.

Assay preparation— Dissolve an accurately weighed quantity of Granules in water by shaking for 30minutes.Quantitatively dilute with water to obtain a solution containing about 0.5mg of flunixin per mL,and mix.Centrifuge a portion of this solution.Transfer 4.0mLof the supernatant layer to a 100-mLvolumetric flask,dilute with 0.1Nsodium hydroxide to volume,and mix.

Procedure— Concomitantly determine the absorbances of the Assay preparationand the Standard preparationat the wavelength of maximum absorbance at about 283nm using 0.1Nsodium hydroxide to set the instrument.Calculate the quantity,in mg,of flunixin (C14H11F3N2O2)in the portion of Granules taken by the formula: in which 296.25and 491.46are the molecular weights of flunixin and flunixin meglumine,respectively;Cis the concentration,in mg per mL,of USP Flunixin Meglumine RSin the Standard preparation,and AUand ASare the absorbances of the Assay preparationand the Standard preparation;respectively.