A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U.

C: A solution in water (1 in 20) meets the requirements of the tests for Chloride 191.

Internal standard solution— Transfer 100 µL of 1,4-dioxane to a 100-mL volumetric flask, dilute with dimethylformamide to volume, and mix.

Standard stock solution— Transfer 1.0 mL of isopropyl alcohol and 0.1 mL of toluene to a 100-mL volumetric flask, dilute with dimethylformamide to volume, and mix. [note—Toluene is used to verify the system suitability.]

Standard solution— Transfer 2.0 mL of the Internal standard solution to a vial. Add 100 µL of Standard stock solution to the Internal standard solution, and mix.

System suitability solution— Use the Standard solution.

Test solution— Transfer between 90 mg to 100 mg of Valganciclovir Hydrochloride, accurately weighed, to a vial. Add 2.0 mL, accurately measured, of Internal standard solution, and mix.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector and a 0.53-mm × 30-m capillary column coated with a 3.0-µm phase G43. The carrier gas is helium, flowing at a rate of about 10.5 mL per minute, and the split ratio is (1:15). The chromatograph is programmed as follows. Initially the column temperature is maintained at 40 for 10 minutes, and then the temperature is increased at a rate of 25 per minute to 240. [note—Condition the column at 240 after each injection for approximately 15 minutes.] The injection port temperature is maintained at about 250, and the detector temperature is maintained at about 300. Chromatograph the System suitability solution as directed for Procedure: the resolution, R, between 1,4-dioxane and toluene is not less than 8; the column efficiency, using the 1,4-dioxane peak, is not less than 6000 theoretical plates; and the relative standard deviation of the response area ratios of the isopropyl alcohol peak to the 1,4-dioxane peak for replicate injections is not more than 15%.

Procedure— Separately inject equal volumes (about 0.5 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the percentages of isopropyl alcohol in the portion of Valganciclovir Hydrochloride taken by the formula: in which V is the volume, in mL, of the Test solution; C is the concentration, in mg per mL, of isopropyl alcohol in the Standard solution; W is the weight, in mg, of Valganciclovir Hydrochloride taken; and RU and RS are the peak area ratios of isopropyl alcohol to the internal standard obtained from the Test solution and the Standard solution, respectively: not more than 1.0% of isopropyl alcohol is found.

test 1—

test 2—

100[rA (rA + rB)]

100[rB (rA + rB)]

Mobile phase— Dissolve 16.2 g of perchloric acid in 1000 mL of water, and mix. Pass this solution through a filter having a 0.5-µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Test solution— Transfer about 10 mg of Valganciclovir Hydrochloride, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with 0.001 N hydrochloric acid to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.0-mm×15-cm column that contains packing L66. The column temperature is maintained at ambient temperature, and the flow rate is about 0.8 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between the second peak of the d-valine ester pair and the first peak of the valganciclovir pair is not less than 3.5; and the column efficiency determined using the second peak of valganciclovir is not less than 1800 theoretical plates.

Procedure— Inject about 20 µL of the Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the enantiomeric purity, in percent, by the following formula: in which rS is the sum of the peak responses of valganciclovir (R and S esters of l-valine) and rIM is the sum of the peak responses of the enantiomeric impurities (R and S esters of d-valine), respectively. The enantiomeric purity is not less than 97.0%.

0.10 M Monobasic ammonium phosphate solution— Dissolve 11.5 g of monobasic ammonium phosphate in about 900 mL of water, adjust with phosphoric acid (85%) to a pH of 2.8 ± 0.2, dilute with water to obtain 1000 mL of solution, and mix.

Mobile phase— Prepare a filtered and degassed mixture of 0.10 M Monobasic ammonium phosphate and methanol (92:8). Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Transfer about 10 mg of USP Valganciclovir Hydrochloride RS and 0.5 mg of USP Methoxymethylguanine RS to a 50-mL volumetric flask, dissolve in and dilute with 0.001 N hydrochloric acid to volume, and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Valganciclovir Hydrochloride RS in 0.001 N hydrochloric acid, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 0.2 mg per mL.

Assay preparation— Dissolve an accurately weighed quantity of Valganciclovir Hydrochloride in 0.001 N hydrochloric acid, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a concentration of about 0.2 mg per mL.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×15-cm column that contains packing L1. The column temperature is maintained at 25, and the flow rate is about 1.0 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: meets the system suitability requirements as specified for Test 1 in the test for Related compounds. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation of the correction factor (CF ) for replicate injections is not more than 1.0%. [note—CF is calculated as directed below in the Procedure.]

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 peak responses. Calculate the percentage, on the anhydrous and solvent-free basis, of C14H22N6O5·HCl in the portion of Valganciclovir Hydrochloride taken by the formula: in which rU is the peak response (sum of two peaks for valganciclovir diastereomers) obtained from the Assay preparation; WU is the weight, in mg, of Valganciclovir Hydrochloride in the Assay preparation; CF is the correction factor; and SU is the total percent of solvent and water in the test sample.