Packaging and storage— Preserve in well-closed containers,preferably at controlled room temperature.

USP Reference standards á11ñ— USP Neomycin Sulfate RS.

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

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— Proceed as directed under Antibiotics—Microbial Assays á81ñ,using an accurately weighed portion of Ointment,equivalent to about 3.5mg of neomycin,shaken in a separator with about 50mLof ether,and extracted with four 20-mLportions of Buffer No.3.Combine the aqueous extracts,and dilute with Buffer No.3to an appropriate volume to obtain a stock solution of convenient concentration.Dilute this stock solution quantitatively and stepwise with Buffer No.3to obtain a Test Dilutionhaving a concentration assumed to be equal to the median dose level of the Standard.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 1343

Phone Number:1-301-816-8335