A:Ultraviolet Absorption 197U —

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

Medium: water; 900 mL.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Procedure— Determine the amount of C10H13N5O4 dissolved employing the procedure set forth in the Assay, making any necessary modifications.

Tolerances— Not less than 75% (Q) of the labeled amount of C10H13N5O4 is dissolved in 45 minutes.

Mobile phase, Standard stock solution, Zidovudine related compound C standard stock solution, and Chromatographic system— Proceed as directed in the Assay under Zidovudine.

Standard solution— Proceed as directed for Standard preparation in the Assay.

Test solution— Proceed as directed for Assay preparation in the Assay.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the quantity, in mg, of zidovudine related compound C (thymine) in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Zidovudine Related Compound C RS in the Standard solution; rU and rS are the peak responses of zidovudine related compound C (thymine) obtained from the Test solution and the Standard solution, respectively; and Q is the quantity, in mg, of zidovudine in the portion of Capsules taken, as determined in the Assay: not more than 3.0% is found.

(Official January 1, 2007)

Mobile phase, Standard stock solution, and Zidovudine related compound C standard stock solution— Prepare as directed in the Assay under Zidovudine.

Standard preparation— Transfer 10.0 mL of Standard stock solution and 1.0 mL of Zidovudine related compound C standard stock solution to a 100-mL volumetric flask, add 25 mL of water, mix, dilute with methanol to volume, and mix.

Assay preparation— Weigh the contents of not fewer than 20 Capsules, mix, and transfer an accurately weighed portion of the powder, equivalent to about 100 mg of zidovudine, to a 100-mL volumetric flask. Dissolve in a mixture of methanol and water (75:25), sonicate for 20 minutes, and dilute with a mixture of methanol and water (75:25) to volume. Allow the solids to settle, and transfer 10.0 mL of the supernatant layer to a 100-mL volumetric flask. Dilute with a mixture of methanol and water (75:25) to volume, and filter, discarding the first 4 mL of the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 265-nm detector and a 4.0-mm × 25-cm column that contains packing L1 and a 3.2-mm × 1.5-cm guard column containing packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.2 for zidovudine related compound C (thymine) and 1.0 for zidovudine; the resolution, R, between zidovudine and zidovudine related compound C (thymine) is not less than 5.0; 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 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of zidovudine (C10H13N5O4) in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Zidovudine RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.