(Official January 1, 2007)

Mobile phase and Chromatographic system—Proceed as directed in the Assay under Chloramphenicol.

Standard preparation— Transfer about 40 mg of USP Chloramphenicol RS, accurately weighed, to a 100-mL volumetric flask, dissolve in methanol, dilute with methanol to volume, and mix. Transfer 10.0 mL of the resulting solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Filter a portion of this solution through a 0.5-µm or finer porosity filter, and use the clear filtrate as the Standard preparation.

Assay preparation— Transfer an accurately weighed quantity of Chloramphenicol Cream, equivalent to about 40 mg of chloramphenicol, to a 100-mL volumetric flask, add about 80 mL of methanol, and sonicate for about 10 minutes. Cool to room temperature, dilute with methanol to volume, and mix. Transfer 10.0 mL of the resulting solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Filter a portion of this solution through a 0.5-µm or finer porosity filter, and use the clear filtrate as the Assay preparation.

Procedure— Proceed as directed for Procedure in the Assay under Chloramphenicol. Calculate the quantity, in mg, of C11H12Cl2N2O5 in the portion of Cream taken by the formula: in which the terms are as defined therein.