Mobile phase— Prepare 0.01Mof dibasic ammonium phosphate in water,and adjust with phosphoric acid to a pHof 3.0.Prepare a filtered and degassed mixture of this solution and acetonitrile (70:30).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Tetracaine Hydrochloride RSin water to obtain a solution having a known concentration of about 0.1mg per mL.

Assay preparation— Transfer an accurately measured volume of Ophthalmic Solution,equivalent to about 10mg of tetracaine hydrochloride,to a 100-mLvolumetric flask,dilute with water to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×25-cm column containing packing L10.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 500theoretical plates;the tailing factor for the analyte peak is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C15H24N2O2·HCl in each mLof the Ophthalmic Solution taken by the formula: in which Cis the concentration,in mg per mL,of USP Tetracaine Hydrochloride RSin the Standard preparation;Vis the volume,in mL,of Ophthalmic Solution taken;and rUand rSare the tetracaine peak responses obtained from the Assay preparationand the Standard preparation,respectively.