A: Infrared Absorption 197K.

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

Test solution: dimethyl sulfoxide.

Standard solution: dimethyl sulfoxide.

Eluant: a mixture of chloroform, methanol, and ammonium hydroxide (80:20:2).

Visualization: 1.

Application volume: 5 µL.

Limit: 1%.

Solvent— Use dimethyl sulfoxide.

(Official January 1, 2007)

Change to read:

Mobile phase— Prepare a filtered and degassed solution of glacial acetic acid in water (1 in 1000). Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution 1— Dissolve accurately weighed quantities of USP Acyclovir RS and guanine in 0.1 N sodium hydroxide, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having known concentrations of about 0.1 mg of each per mL.

System suitability solution 2— Dissolve an accurately weighed quantity of guanine in 0.1 N sodium hydroxide, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution having a known concentration of about 0.7 µg per mL.

Guanine standard preparation— Transfer about 8.75 mg of guanine, accurately weighed, to a 500-mL volumetric flask. Dissolve in 50 mL of 0.1 N sodium hydroxide, dilute with water to volume, and mix. Transfer 2.0 mL of this solution to a 50-mL volumetric flask, dilute with 0.01 N sodium hydroxide to volume, and mix to obtain a solution having a concentration of about 0.7 µg per mL.

Standard preparation— Dissolve about 25 mg of USP Acyclovir RS, accurately weighed, in 5 mL of 0.1 N sodium hydroxide in a 50-mL volumetric flask, dilute with water to volume, and mix. Transfer 10.0 mL of this solution to a 50-mL volumetric flask, dilute with 0.01 N sodium hydroxide to volume, and mix to obtain a solution having a known concentration of about 0.1 mg of USP Acyclovir RS per mL.

Assay preparation— Dissolve about 100 mg of Acyclovir, accurately weighed, in 20 mL of 0.1 N sodium hydroxide in a 200-mL volumetric flask, dilute with water to volume, and mix. Transfer 10.0 mL of this solution to a 50-mL volumetric flask, dilute with 0.01 N sodium hydroxide 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-cmUSP29 column that contains packing L1. The flow rate is about 3 mL per minute. Chromatograph System suitability solution 1, and record the peak responses as directed for Procedure: the resolution, R, between acyclovir and guanine is not less than 2.0; the tailing factor for the analyte peak is not more than 2; and the relative standard deviation for replicate injections for the acyclovir peak is not more than 2.0%. Chromatograph System suitability solution 2, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation, the Guanine standard preparation, and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for all the peaks. Calculate the quantity, in µg, of guanine in the portion of Acyclovir taken by the formula: in which C is the concentration, in µg per mL, of guanine in the Guanine standard preparation; and rU and rS are the peak responses due to guanine in the Assay preparation and the Guanine standard preparation, respectively: not more than 0.7% of guanine is found. Calculate the quantity, in mg, of C8H11N5O3 in the portion of Acyclovir taken by the formula: in which C is the concentration, in mg per mL, of USP Acyclovir RS in the Standard preparation; and rU and rS are the peak responses due to acyclovir in the Assay preparation and the Standard preparation, respectively.