Mobile phase— Prepare as directed in the Assayunder Meclocycline Sulfosalicylate.

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

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

Procedure— Proceed as directed in the Assayunder Meclocycline Sulfosalicylate.Calculate the quantity,in mg,of meclocycline (C22H21ClN2O8)in the portion of Cream taken by the formula: in which Cis the concentration,in µg per mL,of meclocycline in the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.