A: 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.

B: Transfer 2mLof Injection to a test tube,add 5mLof 1Nhydrochloric acid and a few drops of ammonium reineckate TS:a red-violet precipitate is produced.

0.05M Phosphate buffer— Dissolve 6.805g of monobasic potassium phosphate in 1000mLof water.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and 0.05M Phosphate buffer(65:35).Adjust with phosphoric acid to a pHof 4.7,and mix.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Levocarnitine RSin water to obtain a solution having a known concentration of about 10mg per mL.

System suitability solution— Dissolve accurately weighed quantities of USP Levocarnitine RSand USP Levocarnitine Related Compound A RSin water to obtain a solution having concentrations of about 5.0mg per mLand 0.024mg per mL,respectively.

Assay preparation— Pool the contents of ten containers,and dilute an accurately measured volume of Injection quantitatively with water to obtain a solution having a concentration of about 10mg of levocarnitine per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 205-nm detector and a 3.9-mm ×30-cm column that contains packing L8.The flow rate is maintained at about 1mLper minute.The system is programmed to provide variable mixtures of acetonitrile,Mobile phase,and water.Initially elute 50mLof acetonitrile,then change the composition linearly over the next 20minutes to a mixture of 65%acetonitrile and 35%water.Elute 100mLof this mixture,then change the composition linearly over the following 20minutes to 100%Mobile phase,and allow the chromatograph to proceed for about 3hours.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the resolution,R,between levocarnitine related compound Aand levocarnitine is not less than 1.0;and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 5µL)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 levocarnitine (C7H15NO3)in the portion of Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Levocarnitine RSin the Standard preparation;Lis the labeled quantity,in mg,of levocarnitine in each container;Dis the concentration,in mg per mL,of levocarnitine in the Assay preparation,based on the labeled quantity per container and the extent of dilution;and rUand rSare the levocarnitine peak responses obtained from the Assay preparationand the Standard preparation,respectively.