Standard solutions— Dissolve an accurately weighed quantity of manganese (II)chloride tetrahydrate in water,and quantitatively dilute with water to obtain solutions having known concentrations of 0.9mM,2.7mM,and 4.5mM.

Test stock solution— Transfer 5.0mLof the Injection to a 50-mLvolumetric flask,dilute with water to volume,and mix.

Test solutions— Transfer 1.0,2.0,4.0,and 6.0mLofTest stock solution to individual 100-mLvolumetric flasks,dilute each with water to volume,and mix.These solutions have concentrations of 0.504mM,1.008mM,2.016mM,and 3.024mM,respectively,based on the label claim.

Apparatus— Use a mini-NMRspectrometer with suitable sensitivity (seeApparatus underNuclear Magnetic Resonance á761ñ).

System suitability— Place a portion of each of theStandard solutions into a separate 10-mm specimen tube.Warm to 40for not less than 10minutes,and measure the resonance frequency (T1),at 20MHz.The average T1for replicate measurements must be within 5%of 156ms for the 0.9mMStandard solution,52ms for the 2.7mMStandard solution,and 32ms for the 4.5mMStandard solution.

Procedure— Place an accurately measured portion of eachTest solution into a 10-mm specimen tube.Warm to 40for not less than 10minutes,and measure the resonance frequency (T1)of eachTest solution.Plot 1/T1versus the molarities of theTest solutions,and perform a regression analysis.The slope of the plotted line is the relaxivity.The relaxivity is between 4.0and 5.0sec–1mM–1.

Solution A— Proceed as directed forMobile phase in the test forRelated compounds underGadoversetamide.

Solution B— Prepare a filtered and degassed mixture ofSolution Aand acetonitrile (475:25).

Mobile phase— Use variable mixtures ofSolution AandSolution Bas directed forChromatographic system.Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Standard solutions— Prepare aqueous solutions of USP Gadoversetamide Related Compound A RShaving known concentrations of about 30µg per mL,150µg per mL,and 360µg per mL.

Test solution— Transfer 5.0mLof the Injection to a 50-mLvolumetric flask,dilute with water to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— Proceed as directed in the test forRelated compounds underGadoversetamide.The chromatograph is programmed as follows. Plot the concentration,in µg per mL,of eachStandard solution versus its peak area,and perform a regression analysis to obtain a slope and intercept for the Standard response line.The relative standard deviation for replicate injections of the 360µg per mLStandard solution is not more than 5%;and the correlation coefficient,r,of the regression analysis is not less than 0.995.

Procedure— Separately inject equal volumes (about 50µL)of the Test Solution,theStandard solutions,and water (blank)into the chromatograph,record the chromatograms,and measure the peak responses.Allow about 1hour between injections to remove slow-eluting impurities from the column.Calculate the percentage of gadoversetamide related compound Arelative to the amount of gadoversetamide (C20H34GdN5O10)in the portion of Injection taken,based on the label claim,by the formula: in whichCis the concentration of gadoversetamide related compound Ain theTest solution,in µg per mL,obtained from the Standard response line:not more than 1.0%(w/w)of gadoversetamide related compound Ais found.

Mobile phase,Standard preparations,and Chromatographic system— Proceed as directed in theAssay underGadoversetamide.

Assay preparation— Transfer about 3.0mLof the Injection,accurately measured,to a 1000-mLvolumetric flask,dilute withMobile phase to volume,and mix.

Procedure— Proceed as directed in theAssay underGadoversetamide.Calculate the quantity,in mg per mL,of gadoversetamide (C20H34GdN5O10)in the volume of Injection taken by the formula: in which Cis the concentration,in mg per mL,of gadoversetamide in theAssay preparation,obtained from the Standard response line;and Vis the volume,in mL,of Injection taken.