A: Proceed with Ophthalmic Solution as directed under Identification—Organic Nitrogenous Bases á181ñ.The specified results are obtained.

B: It responds to the tests for Bromide á191ñ.

Standard preparation— Accurately weigh about 50mg of USP Homatropine Hydrobromide RS,dissolve in water,and dilute with water in a volumetric flask to 100mL.Dilute 10.0mLof this solution with water to 50.0mLto obtain a solution having a known concentration of about 100µg per mL.Prepare this solution fresh.

Assay preparation— Transfer a portion of Ophthalmic Solution,equivalent to 50mg of homatropine hydrobromide,to a 100-mLvolumetric flask,and dilute with water to volume.Dilute 10.0mLof this solution with water to 50.0mL.

Procedure— Transfer duplicate 2-mLportions of the Standard preparationand of the Assay preparationto separate glass-stoppered,40-mLcentrifuge tubes.To one set of two tubes add 3mLof water and 1mLof sodium hydroxide solution (1in 100).Heat these tubes in a boiling water bath for 20minutes,and allow to cool to room temperature.To the remaining set of tubes,which serve as blanks for the Standard preparationand the Assay preparation,respectively,add 4mLof water.To each tube,add 2mLof approximately 0.2Mceric sulfate in diluted sulfuric acid (prepared by dissolving 12.6g of ceric ammonium sulfate in 50mLof water and 3mLof sulfuric acid,and diluting with water to 100mL)and 20.0mLof isooctane.Shake by mechanical means for 15minutes,allow the layers to separate,and remove the isooctane from each tube.Concomitantly determine the absorbances of the isooctane solutions from the hydrolyzed aliquots in 1-cm cells at the wavelength of maximum absorbance at about 242nm,with a suitable spectrophotometer,against the respective blanks.Calculate the quantity,in mg,of C16H21NO3·HBr in the portion of Ophthalmic Solution taken by the formula: in which Cis the concentration,in µg per mL,of USP Homatropine Hydrobromide RSin the Standard preparation;and AUand ASare the absorbances of the solutions from the Assay preparationand the Standard preparation,respectively.