(Official January 1, 2007)

Mobile phase— Dissolve 1.1 g of sodium 1-heptanesulfonate in about 400 mL of water. Add 250 mL of acetonitrile and 10 mL of glacial acetic acid, dilute with water to 1000 mL, and mix. Sonicate for 10 minutes, filter, and degas to obtain a solution having a pH of about 3.5. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

Assay preparation— Pipet a volume of Nasal Solution, equivalent to about 25 mg of naphazoline hydrochloride, into a 100-mL volumetric flask, dilute with water to volume, and mix.

Chromatographic system (see Chromatography 621)—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 2 mL per 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 15 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C14H14N2·HCl in each mL of the Nasal Solution taken by the formula: in which C is the concentration, in µg per mL, of USP Naphazoline Hydrochloride RS in the Standard preparation, V is the volume, in mL, of Nasal Solution taken, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.