Mobile phase— Prepare a suitable filtered and degassed 0.01Nsulfuric acid in water solution.

Standard preparation— Using Mobile phaseas a solvent,prepare a solution containing accurately known concentrations of about 0.005mg of USP Fumaric Acid RSper mLand about 0.002mg of USP Maleic Acid RSper mL.

Test preparation— Transfer about 100mg,accurately weighed,of Malic Acid to a 100-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Resolution solution— Using Mobile phaseas a solvent,prepare a solution containing about 1mg of Malic Acid per mL,about 10µg of USP Fumaric Acid RSper mL,and about 4µg of USP Maleic Acid RSper mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 210-nm detector and a 6.5-mm ×30-cm column that contains packing L17.Maintain the temperature of the column at 37±1.The flow rate is about 0.6mLper minute.Chromatograph the Resolution solution,and record the peak responses:the resolution,R,of the maleic acid and malic acid peaks is not less than 2.5,the resolution,R,of the malic acid and fumaric acid peaks is not less than 7.0,and the relative standard deviation of the maleic acid peak for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Test preparationinto the chromatograph,record the chromatograms,and measure the peak responses.The relative retention times are about 0.6for maleic acid,1.0for malic acid,and about 1.5for fumaric acid.Calculate the quantities,in mg,of maleic acid and of fumaric acid in the portion of Malic Acid taken by the formula: in which Cis the concentration,in mg per mL,of the corresponding reference standard in the Standard preparation;and rUand rSare the responses of the corresponding peaks from the Test preparationand the Standard preparation,respectively.Not more than 1.0%of fumaric acid and not more than 0.05%of maleic acid are found.