A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Mobile phase, System suitability solution, and Chromatographic system— Proceed as directed in the Assay.

Test solution— Transfer about 11 mg of Ganciclovir, accurately weighed, to a 50-mL volumetric flask; dissolve in and dilute with Mobile phase to volume; and mix.

Procedure— Inject a volume (about 20 µL) of the Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Ganciclovir taken by the formula: in which ri is the peak response for each impurity in the Test solution; and rs is the sum of the responses of all the peaks: not more than 0.5% of ganciclovir related compound A is found; and not more than 1.5% of total impurities is found.

Trifluoroacetic acid solution— Transfer about 0.5 mL of trifluoroacetic acid to a 1000-mL volumetric flask, dilute with water to volume, and mix.

Mobile phase— Prepare a filtered and degassed mixture of Trifluoroacetic acid solution and acetonitrile (1:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Dissolve accurately weighed quantities of USP Ganciclovir RS and USP Ganciclovir Related Compound A RS in Mobile phase, sonicating if necessary, to obtain a solution having a known concentration of about 0.1 mg of each per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Ganciclovir RS, previously dried under vacuum at 80 for 3 hours, in Mobile phase; and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.22 mg per mL.

Assay preparation— Transfer about 11 mg of Ganciclovir, previously dried under vacuum at 80 for 3 hours and accurately weighed, to a 50-mL volumetric flask; dissolve in and dilute with Mobile phase to volume; and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L9. The flow rate is about 1.5 mL per minute. The column temperature is 40. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.9 for ganciclovir related compound A and 1.0 for ganciclovir; the resolution, R, between ganciclovir and ganciclovir related compound A is not less than 1.4; the column efficiency is not less than 5000 theoretical plates; the tailing factor is not more than 1.4; and the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 20 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 C9H13N5O4 in the portion of Ganciclovir taken by the formula: in which C is the concentration, in mg per mL, of USP Ganciclovir RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.