Tetracycline Hydrochloride Ointment »Tetracycline Hydrochloride Ointment contains not less than 90.0percent and not more than 125.0percent of the labeled amount of C22H24N2O8·HCl. Packaging and storage— Preserve in well-closed containers,preferably at controlled room temperature. USP Reference standards á11ñ USP Tetracycline Hydrochloride RS.USP4-Epianhydrotetracycline Hydrochloride RS. Identification— The chromatogram of the Assay preparationobtained as directed in the Assayexhibits a major peak for tetracycline,the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparationobtained as directed in the Assay. Minimum fill á755ñ: meets the requirements. Water,Method Iá921ñ: not more than 1.0%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel. Assay— Diluting solvent ,Mobile phase,Resolution solution,and Chromatographic system—Prepare as directed in the Assayunder Tetracycline Hydrochloride. Assay preparation— Transfer an accurately weighed portion of Ointment,equivalent to about 300mg of tetracycline hydrochloride,to a glass-stoppered conical flask,add 20mLof cyclohexane,and shake.Add 35mLof methanol,and sonicate for about 20minutes.Filter this solution into a 100-mLvolumetric flask,and rinse the sides of the conical flask with 40mLof methanol,filtering the rinsing through the filter into the volumetric flask.Dilute with methanol to volume,and mix.Transfer 2.0mLof this solution to a 50-mLvolumetric flask,dilute with Diluting solventto volume,and mix. Standard preparation— Dissolve an accurately weighed quantity of USP Tetracycline Hydrochloride RSquantitatively in methanol to obtain a solution having a known concentration of about 1mg per mL.Transfer 6.0mLof this solution to a 50-mLvolumetric flask,dilute with Diluting solventto volume,and mix.This solution contains about 0.12mg of USP Tetracycline Hydrochloride RSper mL. Procedure— Proceed as directed in the Assayunder Tetracycline Hydrochloride.Calculate the quantity,in mg,of C22H24N2O8·HCl in the portion of Ointment taken by the formula: 2.5CP(rU/rS), in which the terms are as defined therein. Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow Expert Committee:(PA7)Pharmaceutical Analysis 7 USP28–NF23Page 1887 Phone Number:1-301-816-8335