A: Infrared Absorption 197M.

B: Ultraviolet Absorption 197U—

Solution: 10 µg per mL.

Medium: alcohol.

Test solution: 30 mg per mL, in methanol.

(Official January 1, 2007)

Mobile phase— Dissolve 990 mg of sodium 1-heptanesulfonate in 890 mL of water, add 10 mL of glacial acetic acid and 1100 mL of methanol, mix, pass through a suitable filter having a 1-µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)—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 1.5 mL per 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 1000 theoretical plates; the capacity factor, k¢, for levobunolol is between 1.0 and 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 20 µL) of the Standard preparation and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Levobunolol Hydrochloride RS in the Standard preparation; and rU and rS are the peak area responses obtained from the Assay preparation and the Standard preparation, respectively.