A: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

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

Medium: water; 900 mL.

Apparatus 2: 75 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C7H15NO3 dissolved, employing the procedure set forth in the Assay, making any necessary modifications.

Tolerances— Not less than 75% (Q) of the labeled amount of C7H15NO3 is dissolved in 30 minutes.

pH 4.5 Phosphate buffer (0.05 M)—Dissolve 6.805 g of monobasic potassium phosphate in 1000 mL of water.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and pH 4.5 Phosphate buffer (0.05 M) (65:35). Adjust with phosphoric acid to a pH of 4.7, and mix. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Levocarnitine RS in water to obtain a solution having a known concentration of about 3 mg per mL.

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

Assay preparation— Transfer 10 Tablets, accurately weighed, to a 500-mL volumetric 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 3 mg of levocarnitine per mL.

Chromatographic system (see Chromatography 621)—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 1 mL per minute. The chromatograph is programmed as follows. Initially elute 50 mL of acetonitrile, then change the composition linearly over the next 20 minutes to a mixture of 65% acetonitrile and 35% water. Elute 100 mL of this mixture, then change the composition linearly over the following 20 minutes to 100% Mobile phase, and allow chromatography to proceed for about 3 hours. 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 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C7H15NO3 in the portion of Tablets taken by the formula: in which L is the labeled amount, in mg, of levocarnitine in each Tablet; D is the concentration, in mg per mL, of levocarnitine in the Assay preparation, based on the labeled quantity per Tablet and the extent of dilution; C is the concentration, in mg per mL, of USP Levocarnitine RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.