A: Thin-Layer Chromatographic Identification Test á201ñ—

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Diluent,Mobile phase,System suitability solution,Standard preparation,Column treatment,and Chromatographic system— Proceed as directed in the Assay.

Test preparation— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Test preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg per mL,of fenoldopam related compound B(C16H16NO3·CH4SO3)in the volume of Injection taken by the formula: in which WSis the weight,in mg,of USP Fenoldopam Related Compound B RStaken;Sis the conversion factor from the fenoldopam related compound Bto the free base (i.e.,0.77026);DSand DUare the dilution factors for the Standard preparationand the Test preparation,respectively (i.e.,0.0001and 0.02);and rUand rSare the average peak responses for fenoldopam related compound Bobtained from the Test preparationand the Standard preparation,respectively:not more than 0.6%is found.

Diluent— Dissolve about 1.38g of monobasic sodium phosphate monohydrate in 1Lof water,adjust with a phosphoric acid solution (1in 9)to a pHof 2.5,and mix.

Mobile phase— Dissolve about 1.38g of monobasic sodium phosphate monohydrate and 1.88g of sodium hexanesulfonate in 1liter of water,adjust with a phosphoric acid solution (1in 9)to a pHof 2.5,and mix.Prepare a filtered and degassed mixture of this solution and methanol (67:33).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Transfer about 2.74mg of USP Fenoldopam Related Compound B RS,accurately weighed,to a 100-mLvolumetric flask.Dissolve in and dilute with Diluentto volume,and mix.

Standard preparation— Transfer about 26.3mg of USP Fenoldopam Mesylate RS,accurately weighed,to a 100-mLvolumetric flask,and dissolve in about 75mLof Diluent.Add,by pipetting,1.0mLof the System suitability solution,dilute with Diluentto volume,and mix.

Assay preparation— Accurately pipet about 0.5mLof Injection into a 25-mLvolumetric flask,dilute with Diluentto volume,and mix.

Column treatment— [NOTE—This treatment is required for new columns only.]Pump a solution of cyclam (1in 1000)through the new column for about 3hours at a flow rate of about 1mLper minute,and then pump Mobile phasefor at least 2hours at the same flow rate.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.0mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the capacity factor,k¢,is between 1and 3;the column efficiency is not less than 1800theoretical plates;and the tailing factor is not more than 2.5.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the capacity factor,k¢,is between 4and 6;the column efficiency is not less than 1800theoretical plates;the tailing factor is not more than 2.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg per mL,of fenoldopam mesylate (C16H16ClNO3·CH4SO3)in the volume of Injection taken by the formula: in which WSis the weight,in mg,of USP Fenoldopam Mesylate RStaken;Sis the conversion factor from the fenoldopam mesylate to the free base (i.e.,0.7610);DSand DUare the dilution factors for the Standard preparationand the Assay preparation,respectively (i.e.,0.01and 0.02);and rUand rSare the fenoldopam peak responses obtained from the Assay preparationand the Standard preparation,respectively.