A:Thin-Layer Chromatographic Identification Test á201ñ—

B: The retention time of the major peak in the chromatogram of theAssay preparation corresponds to that in the chromatogram of theStandard preparation,as obtained in theAssay.

Medium: 0.05Mmonobasic potassium phosphate buffer,pH7.4;1000mL.

Apparatus 2: 75rpm.

Time: 45minutes.

Procedure— Determine the amount of C18H15NO3dissolved by employing UVabsorption at the wavelength of maximum absorbance at about 286nm on 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 Oxaprozin RSin the same Medium (an amount of methanol not exceeding 5%of the final volume can be added to help solubilize the USP Reference Standard).

Tolerances— Not less than 75%(Q)of the labeled amount of C18H15NO3is dissolved in 45minutes.

0.1%Phosphoric acid,pH2.00±0.10— Add concentrated phosphoric acid,dropwise,to water to obtain a pHof 2.00±0.10.

Mobile phase— Prepare a filtered and degassed solution of 0.1%Phosphoric acid,pH2.00±0.10and acetonitrile (55:45).

Standard preparation— Dissolve an accurately weighed quantity of USP Oxaprozin RSin acetonitrile to obtain a solution having a concentration of about 12µg of oxaprozin per mL.

Assay stock preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 60mg of oxaprozin,to a 100-mLvolumetric flask,add about 10mLof water,and sonicate for 10minutes.Add about 40mLof acetonitrile,sonicate for 30minutes,shake by mechanical means for an additional 30minutes,add about 30mLof acetonitrile,and sonicate for 10minutes.Dilute with acetonitrile to volume.

Assay preparation— Quantitatively dilute the Assay stock preparationwith acetonitrile to obtain a solution having a concentration of about 12µg of oxaprozin per mL.

Chromatographic system (seeChromatography á621ñ)— The liquid chromatograph is equipped with a 285-nm detector and a 4.6-mm ×15-cm column that contains 5-µm packing L7.The flow rate is about 1.0mLper minute.Chromatograph theStandard preparation,and record the peak responses as directed forProcedure:the tailing factor 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 20µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of oxaprozin (C18H15NO3)in the portion of Tablets taken by the formula: in which Cis the concentration in mg per mLof USP Oxaprozin RSin theStandard preparation;and rUand rSare the peak responses obtained from theAssay preparation and theStandard preparation,respectively.