A: Prepare a test solution by diluting a suitable volume of Ophthalmic Solution with water,if necessary,to obtain a solution containing about 1mg of carteolol hydrochloride per mL.Separately apply 10µLof the test solution and 10µLof a Standard solution of USP Carteolol Hydrochloride RSin water containing about 1mg per mLto the starting line of a thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Allow the spots to dry.Line a chromatographic chamber with filter paper,and saturate the paper with a solvent system consisting of a mixture of chloroform,methanol,and ammonium hydroxide (50:20:1).Place the plate in the chamber,and develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the chamber,and allow to air-dry.Examine the plate under short-wavelength UVlight:the RFvalue of the principal spot in the chromatogram obtained from the test solution corresponds to that in the chromatogram obtained from the Standard solution.

B: The retention time of the carteolol peak in the chromatogram of the Assay preparationobtained as directed in the Assaycorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

pH6.0buffer ,Mobile phase,Diluent,Standard preparation,Resolution solution,and Chromatographic system—Proceed as directed in the Assayunder Carteolol Hydrochloride.

Assay preparation— Transfer an accurately measured volume of Ophthalmic Solution,equivalent to about 10mg of carteolol hydrochloride,to a 100-mLvolumetric flask,dilute with Diluentto volume,and mix.Filter a portion of this solution through a filter having a porosity of 0.5µm or finer,discarding the first 2mLof the filtrate,and use the filtrate as the Assay preparation.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of C16H24N2O3·HCl in each mLof the Ophthalmic Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Carteolol Hydrochloride RSin the Standard preparation,Vis the volume,in mL,of Ophthalmic Solution taken,and rUand rSare the carteolol peak responses obtained from the Assay preparationand the Standard preparation,respectively.