A: Infrared Absorption á197Kñ.

B: It responds to the tests for Chloride á191ñ.

Phosphate buffer— Transfer 6.8mLof phosphoric acid to a 2000-mLvolumetric flask,add about 1900mLof water,and mix.Adjust with sodium hydroxide solution (1in 2)to a pHof 3.0,dilute with water to volume,and mix.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile,Phosphate buffer,and methanol (56:40:4).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Prepare a solution in Mobile phasecontaining about 0.8mg of USP Apraclonidine Hydrochloride RSper mL.

Test solution— Transfer about 20mg of Apraclonidine Hydrochloride,accurately weighed,to a 25-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 220-nm detector and an 8-mm ×100-mm column that contains packing L7.The flow rate is about 3mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the tailing factor for the apraclonidine peak is not more than 2.2,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject about 20µLof the Test solutioninto the chromatograph,record the chromatogram,and measure the areas for the major peaks.[NOTE—Allow about five times the elution time of apraclonidine before making the next injection.]Calculate the percentage of each peak,other than the solvent peak and the apraclonidine peak,in the specimen of Apraclonidine Hydrochloride taken by the same formula: in which riis the response of each peak other than the principal peak,and rtis the sum of the responses of all of the peaks,excluding that of the solvent peak:not more than 1.0%for any individual impurity and not more than 2.0%total impurities are found.