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: Dissolve 1Tablet in 5mLof water,filter,and add 5mLof 1Nhydrochloric acid.Place 2mLof the filtrate in a test tube and add a few drops of ammonium reineckate TS:a red-violet precipitate is produced.

Medium: water;900mL.

Apparatus 2: 75rpm.

Time: 30minutes.

Procedure— Determine the amount of C7H15NO3dissolved,employing the procedure set forth in the Assay,making any necessary modifications.

Tolerances— Not less than 75%(Q)of the labeled amount of C7H15NO3is dissolved in 30minutes.

pH4.5Phosphate buffer (0.05M)—Dissolve 6.805g of monobasic potassium phosphate in 1000mLof water.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and pH4.5Phosphate buffer(0.05M)(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 3mg per mL.

Resolution solution— Dissolve accurately weighed quantities of USP Levocarnitine RSand USP Levocarnitine Related Compound A RSin water to obtain a solution having concentrations of about 1.5mg and 0.007mg per mL,respectively.

Assay preparation— Transfer 10Tablets,accurately weighed,to a 500-mLvolumetric flask,and add water to volume.Shake until the Tablets have disintegrated completely,and pass through a filter having a 0.45-µm porosity.Dilute the filtrate quantitatively with water to obtain a solution having a known concentration of about 3mg 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 10-µm packing L8.The flow rate is maintained at about 1mLper minute.The chromatograph is programmed as follows.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 chromatography to proceed for about 3hours.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the resolution,R,between crotonoylbetaine (levocarnitine related compound A)and levocarnitine is not less than 1.0.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)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 C7H15NO3in the portion of Tablets taken by the formula: in which Lis the labeled amount,in mg,of levocarnitine in each Tablet;Dis the concentration,in mg per mL,of levocarnitine in the Assay preparation,based on the labeled quantity per Tablet and the extent of dilution;Cis the concentration,in mg per mL,of USP Levocarnitine RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.