(Official January 1, 2007)

Mobile phase— Prepare as directed in the Assay under Meclocycline Sulfosalicylate.

Standard preparation— Transfer 36 mg of USP Meclocycline Sulfosalicylate RS, accurately weighed, to a 50-mL volumetric flask, dilute with methanol to volume, and mix. Transfer 2.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix to obtain a solution having a known concentration of about 10 µg of meclocycline per mL.

Assay preparation— Transfer an accurately weighed quantity of Cream, equivalent to about 5 mg of meclocycline, to a glass-stoppered, 50-mL centrifuge tube, add 20 mL of methanol and 20 mL of 0.025 N sulfuric acid, and shake vigorously for 15 minutes. Transfer the solution to a 50-mL volumetric flask, rinsing the centrifuge tube with two 5-mL portions of methanol and adding the rinsings to the flask, dilute with methanol to volume, and mix. Centrifuge a portion of this solution for 5 minutes, transfer 5 mL of the supernatant to a 50-mL volumetric flask, dilute with Mobile phase to volume, mix, and filter.

Procedure— Proceed as directed in the Assay under Meclocycline Sulfosalicylate. Calculate the quantity, in mg, of meclocycline (C22H21ClN2O8) in the portion of Cream taken by the formula: in which C is the concentration, in µg per mL, of meclocycline in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.