Levocarnitine Oral Solution
Levocarnitine Oral Solution is a solution of levocarnitine in water, and it contains suitable antimicrobial agents. It may contain a suitable flavor. It contains NLT 90.0% and NMT 110.0% of the labeled amount of levocarnitine (C7H15NO3).
•  A. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, both relative to the internal standard, as obtained in the Assay.
•  Procedure
Buffer:  0.05 M phosphate buffer, pH 2.4, prepared by mixing 11.5 mL of phosphoric acid, 1900 mL of water, and about 100 mL of 1 N sodium hydroxide
Mobile phase:  Dissolve 555 mg of sodium 1-heptanesulfonate in 980 mL of Buffer with stirring. Add 20 mL of methanol, and mix.
Internal standard solution:  0.02 mg/mL of p-aminobenzoic acid in water
Standard solution:  Transfer about 10 mg of USP Levocarnitine RS to a 5-mL volumetric flask, add 1.0 mL of the Internal standard solution, and dilute with water to volume.
Sample stock solution:  Equivalent to 10 mg/mL of levocarnitine in water from an accurately measured volume of Oral Solution
Sample solution:  Wash a 10-mm × 4-cm disposable column containing 500 mg of packing L1, in order, with two column volumes of methylene chloride, two column volumes of methanol, and three column volumes of water. Pipet 5.0 mL of the Sample stock solution into the washed disposable column, and rinse the column twice with 6.0-mL portions of water. Collect the filtrate and washings in a 25-mL volumetric flask, add 5.0 mL of the Internal standard solution, and dilute with water to volume.
Chromatographic system 
Mode:  LC
Detector:  UV 225 nm
Column:  3.9-mm × 30-cm; 10-µm packing L1
Flow rate:  1.5 mL/min
Injection size:  40 µL
System suitability 
Sample:  Standard solution
[Note—The relative retention times for levocarnitine and p-aminobenzoic acid are 0.56 and 1.0, respectively. ]
Suitability requirements 
Resolution:  NLT 1.5 between the levocarnitine and internal standard peaks
Relative standard deviation:  NMT 2.0% for levocarnitine
Samples:  Standard solution and Sample solution
Calculate the percentage of the labeled amount of levocarnitine (C7H15NO3) in the portion of Oral Solution taken:
Result = (RU/RS) × (CS/CU) × 100
RU== peak area ratio of levocarnitine to p-aminobenzoic acid from the Sample solution
RS== peak area ratio of levocarnitine to p-aminobenzoic acid from the Standard solution
CS== concentration of USP Levocarnitine RS in the Standard solution (mg/mL)
CU== nominal concentration of levocarnitine in the Sample solution (mg/mL)
Acceptance criteria:  90.0%–110.0%
•  pH 791: 4.0–6.0
•  Packaging and Storage: Preserve in tight containers.
•  USP Reference Standards 11
USP Levocarnitine RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Natalia Davydova
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
Reference Standards RS Technical Services
USP35–NF30 Page 3667