Packaging and storage— Preserve in well-closed containers containing not more than 60g,unless labeled solely for hospital use,preferably at controlled room temperature.

USP Reference standards á11ñ— USP Bacitracin Zinc RS.

Thin-layer chromatographic identification test á201BNPñ: meets the requirements.

Minimum fill á755ñ: meets the requirements.

Water,Method Iá921ñ: not more than 0.5%,20mLof a mixture of toluene and methanol (7:3)being used in place of methanol in the titration vessel.

Assay— Proceed as directed under Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Ointment shaken with about 50mLof ether in a separator,and extracted with four 20-mLportions of Buffer No.1.Combine the buffer extracts,and dilute with Buffer No.1to an appropriate volume to obtain a stock solution.Add sufficient 0.01Nhydrochloric acid to an accurately measured portion of the stock solution so that the amount of hydrochloric acid in the Test Dilutionwill be the same as in the median dose level of the Standard,and quantitatively dilute with Test Dilutionhaving a bacitracin concentration assumed to be equal to the median dose level of the Standard.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 214

Phone Number:1-301-816-8335