Mobile phase— Dissolve 1.1g of sodium 1-heptanesulfonate in about 400mLof water.Add 250mLof acetonitrile and 10mLof glacial acetic acid,dilute with water to 1000mL,and mix.Sonicate for 10minutes,filter,and degas to obtain a solution having a pHof about 3.5.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Naphazoline Hydrochloride RSin water,and dilute quantitatively,and stepwise if necessary,with water to obtain a solution having a known concentration of about 250µg per mL.

Assay preparation— Pipet a volume of Nasal Solution,equivalent to about 25mg of naphazoline hydrochloride,into 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-mm ×30-cm column that contains packing L11.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed under Procedure:the tailing factor for the naphazoline hydrochloride peak is not more than 2.0,and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 15µL)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 C14H14N2·HCl in each mLof the Nasal Solution taken by the formula: in which Cis the concentration,in µg per mL,of USP Naphazoline Hydrochloride RSin the Standard preparation,Vis the volume,in mL,of Nasal Solution taken,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.