Medium: pH6.8Phosphate buffer(see Buffer Solutionsin the section Reagents,Indicators,and Solutions);1000mL.

Apparatus 1: 100rpm.

Time: 30minutes.

Procedure— Determine the amount of C17H21NO3dissolved from UVabsorbances at the wavelength of maximum absorbance at about 274nm of filtered portions of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Etodolac RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C17H21NO3is dissolved in 30minutes.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile,water,and phosphoric acid (500:500:0.25).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Dissolve suitable quantities of USP Etodolac Related Compound A RSand USP Etodolac RSin Mobile phaseto obtain a solution containing about 0.01mg of etodolac related compound Aand 0.2mg of etodolac per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Etodolac RSin Mobile phaseto obtain a solution having a known concentration of about 0.2mg per mL.Prepare this solution fresh daily.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 1000mg of etodolac,to a 500-mLvolumetric flask,add 300mLof Mobile phase,shake for 15minutes,sonicate for 5minutes,cool,dilute with Mobile phaseto volume,and mix.Allow to settle for 10minutes.Pipet 10.0mLof the solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Pass the solution through a filter having a porosity of 0.45µm or less.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 274-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for etodolac related compound Aand 1.0for etodolac;the resolution,R,between etodolac related compound Aand etodolac is not less than 2;the tailing factor is not more than 2;and the relative standard deviation for replicate injections is not more than 2%.

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 etodolac (C17H21NO3)in the portion of Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Etodolac RSin the Standard preparation;and rUand rSare the etodolac peak responses obtained from the Assay preparationand the Standard preparation,respectively.