Packaging and storage— Preserve in tight,light-resistant containers.

Identification— The residue obtained by evaporating,on a steam bath,a volume of Topical Solution,equivalent to about 200mg of benzethonium chloride,responds to the Identificationtests under Benzethonium Chloride.

Oxidizing substances— To 5mLadd 0.5mLof potassium iodide TSand a few drops of 3Nhydrochloric acid:the solution does not acquire a yellow color.

Limit of nitrites— To 1drop of Topical Solution on a spot plate add 1drop each of glacial acetic acid,sulfanilic acid in acetic acid (1in 100),and 1-naphthylamine–acetic acid solution (prepared by boiling 30mg of 1-naphthylamine in 70mLof water,decanting the colorless solution from the blue-violet residue,and mixing with 30mLof glacial acetic acid):no red color develops in the resulting solution within 10minutes.

Assay— Transfer a volume of Topical Solution,equivalent to about 200mg of benzethonium chloride,to a glass-stoppered flask,and proceed as directed in the Assayunder Benzethonium Chloride,beginning with “Add 0.4mLof bromophenol blue solution (1in 2000)”.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 227

Phone Number:1-301-816-8394