A: Weigh a portion of finely powdered Tablets,equivalent to about 50mg of ethacrynic acid,and transfer to a separator containing 25mLof 0.1Nhydrochloric acid.Extract with two 40-mLportions of methylene chloride,filter the extracts into a 100-mLvolumetric flask,and dilute with methylene chloride to volume.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,evaporate in a gentle current of air to dryness,and promptly dissolve the residue in a portion of a 9in 1000mixture of hydrochloric acid in anhydrous methanol,then dilute with the acidic methanol to volume:the UVabsorption spectrum of the solution exhibits maxima and minima at the same wavelengths as that of a solution of USP Ethacrynic Acid RSin the acidic methanol containing 50µg per mL,concomitantly measured.

B: Aportion of powdered Tablets,equivalent to 25mg of ethacrynic acid,responds to Identificationtest Cunder Ethacrynic Acid.

Medium: 0.1Mphosphate buffer,prepared by mixing 13.6g of monobasic potassium phosphate and 96.2mLof 0.1Nsodium hydroxide with water to obtain 1000mLof a solution having a pHof 8.0±0.05;900mL.

Apparatus 2: 50rpm.

Time: 45minutes.

Procedure— Determine the amount of C13H12Cl2O4dissolved from UVabsorbances at the wavelength of maximum absorbance at about 277nm of filtered portions of the solution under test,suitably diluted with Medium,in comparison with a Standard solution having a known concentration of USP Ethacrynic Acid RSin the same medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C13H12Cl2O4is dissolved in 45minutes.

Procedure for content uniformity— Add 1Tablet to a 100-mLvolumetric flask containing 10mLof water,and allow to stand for 15minutes,shaking occasionally until the tablet is disintegrated.Add a 9in 1000mixture of hydrochloric acid in methanol to volume,and mix.Filter a portion of the mixture,and pipet a volume of the filtrate,equivalent to 5mg of ethacrynic acid,into a 100-mLvolumetric flask.Dilute with the acidic methanol to volume,and mix.Dissolve an accurately weighed quantity of USP Ethacrynic Acid RSin the acidic methanol,and dilute quantitatively and stepwise with the same solvent to obtain a Standard solution having a known concentration of about 50µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 269nm,with a suitable spectrophotometer,using the acidic methanol as the blank.Calculate the quantity,in mg,of C13H12Cl2O4in the Tablet by the formula: in which Tis the labeled quantity,in mg,of ethacrynic acid in the Tablet,Dis the concentration,in µg per mL,of ethacrynic acid in the solution from the Tablet,on the basis of the labeled quantity per Tablet and the extent of dilution,Cis the concentration,in µg per mL,of USP Ethacrynic Acid RSin the Standard solution,and AUand ASare the absorbances of the solution from the Tablet and the Standard solution,respectively.

Triethylamine solution— Mix 10mLof triethylamine and about 900mLof water in a 1-liter volumetric flask.Adjust with phosphoric acid to a pHof 6.8±0.1,dilute with water to volume,mix,and filter.

Solvent mixture— Prepare a mixture of water and acetonitrile (3:2).

Mobile phase— Prepare a filtered and degassed mixture of Triethylamine solutionand acetonitrile (3:2).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Ethacrynic Acid RSin Solvent mixture,and dilute quantitatively with Solvent mixture,to obtain a solution having a known concentration of about 0.5mg per mL.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 50mg of ethacrynic acid,to a 100-mLvolumetric flask,add about 80mLof Solvent mixture,and shake or sonicate to dissolve the ethacrynic acid.Dilute with Solvent mixtureto 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 1mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the column efficiency determined from the analyte peak is not less than 1200theoretical plates,the tailing factor for the analyte peak is not more than 2,the capacity factor,k¢,is not less than 0.8,and the relative standard deviation for replicate injections is not more than 1.0.%.

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,of C13H12Cl2O4in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Ethacrynic Acid RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.