A:Infrared Absorption á197Kñ—

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Medium: water;900mL.

Apparatus 2: 50rpm.

Time: 30minutes.

Procedure— Determine the amount of C10H13N5O4dissolved by employing the procedure set forth in the Assay,using a filtered portion of the solution under test as the Assay preparationin comparison with a Standard solution having a known concentration of USP Zidovudine RSin the same Medium.

Tolerances— Not less than 80%(Q)of the labeled amount of C10H13N5O4is dissolved in 30minutes.

PROCEDURE FOR CONTENT UNIFORMITY—

Mobile phase,Standard preparation,andChromatographic system— Proceed as directed in the Assay.

Test preparation— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Test preparationinto the chromatograph,record the chromatograms,and measure all of the peak responses.Calculate the percentage of each impurity in the portion of Tablets taken by the formula: in which Fis the relative response factor and is equal to 0.59for any peak with a relative retention time of 0.17,and is equal to 1.00for all other peaks;riis the peak response for each impurity obtained from the Test preparation;and rSis the peak response for zidovudine obtained from the Standard preparation:not more than 1.5%of an impurity with a relative retention time of 0.17is found;not more than 0.2%of any other impurity is found;and not more than 2.0%of total impurities is found.

Mobile phase— Dissolve 3.0g of sodium acetate and 1.3g of sodium 1-octanesulfonate in 900mLof water.Add 90mLof methanol and 40mLof acetonitrile,and mix.Adjust with glacial acetic acid to a pHof 5.3,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Zidovudine RSin a volume of methanol,equivalent to not more than 1.2%of the total flask volume,dilute with water to volume,and mix to obtain a final solution having a known concentration of about 0.12mg per mL.

Assay preparation— Transfer a counted number of Tablets,equivalent to 1500mg of zidovudine,to a 500-mLvolumetric flask.Add about 50mLof water,and shake by mechanical means for 30minutes to disperse the Tablets.Add about 150mLof methanol,and sonicate for 10minutes.Dilute with water to volume,and mix.Pipet 4.0mLinto a 100-mLvolumetric flask,and dilute with water to volume.Mix,and pass a portion of the solution through a suitable nylon filter,discarding the first 2mLof the filtrate.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 265-nm detector and a 4.6-mm ×15-cm column that contains packing L1.The flow rate is about 1.3mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between zidovudine and a peak having a relative retention time of about 1.2is not less than 2.5;the tailing factor for the zidovudine peak 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 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 zidovudine (C10H13N5O4)in each Tablet taken by the formula: in which Cis the concentration,in mg per mL,of USP Zidovudine RSin the Standard preparation;Nis the number of Tablets taken for the Assay preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.