Reagent A— Dissolve 8.5g of tetrabutylammonium hydrogen sulfate in 80mLof water.Add 3.4mLof phosphoric acid,and adjust with 10Nsodium hydroxide to a pHof 7.55.

Mobile phase— Add 20mLof Reagent Ato a mixture of 880mLof water and 100mLof acetonitrile,mix,filter,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of 1,1-cyclobutanedicarboxylic acid in Mobile phaseto obtain a solution having a known concentration of about 0.5mg per mL.Transfer 2.0mLof this solution to a 200-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

System suitability solution— Mix 1.0mLof the Standard solutionwith 1.0mLof Standard preparation,prepared as directed in the Assay.

Test solution— Transfer about 50mg of Carboplatin,accurately weighed,to a 50-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 a 4.0-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph replicate injections (about 100µL)of the System suitability solution,record the chromatograms,and measure the peak responses:the relative retention times are about 0.65for carboplatin and 1.0for 1,1-cyclobutanedicarboxylic acid;the column efficiency,determined from the 1,1-cyclobutanedicarboxylic acid peak,is not less than 1500theoretical plates;the resolution,R,between carboplatin and 1,1-cyclobutanedicarboxylic acid peaks is not less than 2.5;and the relative standard deviation for replicate injections is not more than 10%.

Procedure— Separately inject equal volumes (about 100µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses for the 1,1-cyclobutanedicarboxylic acid peaks.Calculate the percentage of 1,1-cyclobutanedicarboxylic acid in the portion of Carboplatin taken by the formula: in which Cis the concentration,in µg per mL,of 1,1-cyclobutanedicarboxylic acid in the Standard solution,Wis the weight,in mg,of Carboplatin taken to prepare the Test solution,and rUand rSare the peak responses for 1,1-cyclobutanedicarboxylic acid obtained from the Test solutionand the Standard solution,respectively:not more than 0.5%is found.

Mobile phase,Chromatographic system,and Procedure— Proceed as directed in the Assay.

Standard solution— Quantitatively dilute a volume of the Standard preparation,prepared as directed in the Assay,with water to obtain a solution having a known concentration of about 2.5µg of USP Carboplatin RSper mL.

Test solution— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.The sum of the peak responses,excluding the carboplatin and 1,1-cyclobutanedicarboxylic acid responses,from the Test solution,is not more than 2times the carboplatin response from the Standard solution,and no single peak response is greater than that of the carboplatin peak from the Standard solution:not more than 0.25%of any individual impurity is found,and the sum of all impurities is not more than 0.5%.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and water (87:13).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Carboplatin RSin water,and quantitatively dilute with water to obtain a solution having a known concentration of about 1mg per mL.[NOTE—Use this solution within 2hours.]

Assay preparation— Transfer about 50mg of Carboplatin,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.[NOTE—Use this solution within 2hours.]

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 230-nm detector and a 4.0-mm ×30-cm column that contains packing L8.The flow rate is about 2.0mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the capacity factor,k¢,is not less than 3.0,the column efficiency is not less than 2500theoretical plates,the tailing factor is not more than 2.5,and the relative standard deviation for replicate injections is not more than 1.2%.

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,of C6H12N2O4Pt in the portion of Carboplatin taken by the formula: in which Cis the concentration,in mg per mL,of USP Carboplatin RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.