A: Infrared Absorption á197Mñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 10µg per mL.

Medium: alcohol.

Test solution: 30mg per mL,in methanol.

Mobile phase— Dissolve 990mg of sodium 1-heptanesulfonate in 890mLof water,add 10mLof glacial acetic acid and 1100mLof methanol,mix,pass through a suitable filter having a 1-µm or finer porosity,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Levobunolol Hydrochloride RSin Mobile phaseto obtain a solution having a known concentration of about 1.0mg per mL.

Assay preparation— Transfer about 100mg of Levobunolol Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 1000theoretical plates;the capacity factor,k¢,for levobunolol is between 1.0and 1.4,the tailing factor for the analyte peak is not more than 2.5,and the relative standard deviation for replicate injections is not more than 0.5%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the area responses for the major peaks.Calculate the quantity,in mg,of C17H25NO3·HCl in the portion of Levobunolol Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Levobunolol Hydrochloride RSin the Standard preparation;and rUand rSare the peak area responses obtained from the Assay preparationand the Standard preparation,respectively.