A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Color of solution— Dissolve 1.0g in 10.0mLof methanol:the color of the solution is not more intense than 10mLof a Standard solution containing 4.8µg per mLof potassium chromate in water,when compared in matched color-comparison tubes (see Visual Comparisonunder Spectrophotometry and Light-Scattering á851ñ).

Turbidity— The test solution prepared as directed under Color of solutionhas no more turbidity than 10mLof methanol,when compared in matched color-comparison tubes (see Visual Comparisonunder Spectrophotometry and Light-Scattering á851ñ).

Solution A— Dissolve 4g of monobasic potassium phosphate in 1000mLwater.Adjust with 1Mphosphoric acid,prepared by diluting 115g of phosphoric acid and diluting with water to 1000mL,to a pHof 4.0.

Solution B— Combine 750mLof acetonitrile with 250mLof Solution A.

Blank— Solution A.

Mobile phase— Use variable mixtures of Solution Aand Solution Bas directed for Chromatographic system(see System Suitabilityunder Chromatography á621ñ).

Acetylclonidine solution— Dissolve about 1mg of USP Clonidine Related Compound A RSin 1mLof acetonitrile,and dilute with Solution Ato 20mL.

System suitability solution— Combine an accurately weighed quantity of USP Clonidine RSand an appropriate volume ofAcetylclonidine solution,and dissolve in and dilute with Solution Ato obtain a solution containing about 0.86mg per mLand 0.86µg per mL,respectively.

Standard solution— Dissolve an accurately weighed quantity of USP Clonidine RSin Solution A,and dilute quantitatively,and stepwise if necessary,with Solution Ato obtain a solution having a known concentration of about 8.6µg per mL.

Test solution— Transfer about 43mg of Clonidine,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with Solution Ato volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with 210-nm detector and a 3.0-mm ×15-cm column that contains 5-µm packing L56.The column temperature is maintained at 40.The flow rate is about 1.5mLper minute.The chromatograph is programmed as follows. Chromatograph the Blankand the System suitability solution,and record the peak responses as directed for Procedure:the resolution factor between clonidine and acetylclonidine is not less than 5;and the tailing factor for clonidine is less than 2.5.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections of the Standard solutionis not more than 5%.

Procedure— Separately inject equal volumes (about 5µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses for all peaks not observed in the Blank.Calculate the percentage of each impurity in the Clonidine taken by the formula: in which Cis the concentration,in µg per mL,of USP Clonidine RSin the Standard solution;Wis the weight,in mg,of Clonidine used to prepare the Test solution;riis the peak response for each impurity in the Test solution;and rSis the peak response of clonidine in the Standard solution:not more than 0.1%of any individual impurity is found;and not more than 0.2%of total impurities is found.