A: Infrared Absorption á197Mñ.

B: Ultraviolet Absorption á197Uñ—

Solution :100µg per mL.

Medium: water.

C: To a solution of about 50mg in 3mLof water add 1mLof 6Nammonium hydroxide,filter,and acidify the filtrate with nitric acid:the filtrate responds to the tests for Chloride á191ñ.

Mobile phase— Prepare a suitable degassed solution of water,methanol,1Msodium acetate,and glacial acetic acid (46:40:10:4).

Standard preparation— Prepare a solution in Mobile phaseof USP Oxymetazoline Hydrochloride RShaving a known concentration of about 0.5mg per mL.

Assay preparation— Transfer about 25mg of Oxymetazoline Hydrochloride,accurately weighed,to a 50-mLvolumetric flask,dissolve in Mobile phase,dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×0.25-m column that contains packing L9.The flow rate is about 1mLper minute.Chromatograph five replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor is not more than 2.0and the relative standard deviation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the response for the major peak.Calculate the quantity,in mg,of C16H24N2O·HCl in the portion of Oxymetazoline Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Oxymetazoline RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.