Packaging and storage— Preserve in collapsible tubes or in well-closed,light-resistant containers.

USP Reference standards á11ñ— USP Chlortetracycline Hydrochloride RS.

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 quantity of Ointment,equivalent to about 30mg of chlortetracycline hydrochloride,shaken in a separator with about 50mLof ether,and extracted with four 20-mLportions of 0.01Nhydrochloric acid.Combine the aqueous extracts in a 100-mLvolumetric flask,dilute with 0.01Nhydrochloric acid to volume,and mix.Dilute this stock solution quantitatively and stepwise with water to obtain a Test Dilutionhaving a concentration assumed to be equal to the medium dose level of the Standard.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 459

Phone Number:1-301-816-8335