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Threonine
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C4H9NO3 119.12

L-Threonine.
L-Threonine [72-19-5].
» Threonine contains not less than 98.5 percent and not more than 101.5 percent of C4H9NO3, as L-threonine, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
USP Reference standards 11— USP L-Proline RS. USP L-Threonine RS.
Specific rotation 781S: between 26.7 and 29.1.
Test solution: 60 mg per mL, in water.
pH 791: between 5.0 and 6.5 in a solution (1 in 20).
Loss on drying 731— Dry it at 105 for 3 hours: it loses not more than 0.2% of its weight.
Residue on ignition 281: not more than 0.4%.
Chloride 221— A 0.73-g portion shows no more chloride than corresponds to 0.50 mL of 0.020 N hydrochloric acid (0.05%).
Sulfate 221— A 0.33-g portion shows no more sulfate than corresponds to 0.10 mL of 0.020 N sulfuric acid (0.03%).
Iron 241: 0.003%.
Chromatographic purity—
Adsorbent: 0.25-mm layer of chromatographic silica gel mixture.
Diluent— Prepare by mixing 10 mL of hydrochloric acid with sufficient water to make 1000 mL.
Test solution— Dissolve an accurately weighed quantity of Threonine in 2 N hydrochloric acid to obtain a solution having a concentration of 10 mg per mL. Apply 5 µL.
Standard solution— Dissolve an accurately weighed quantity of USP L-Threonine RS in Diluent to obtain a solution having a known concentration of about 0.05 mg per mL. Apply 5 µL. [NOTE—This solution has a concentration equivalent to about 0.5% of that of the Test solution.]
System suitability solution— Prepare a solution in Diluent containing 0.4 mg each of USP L-Threonine RS and USP L-Proline RS per mL. Apply 5 µL.
Spray reagent— Dissolve 0.2 g of ninhydrin in 100 mL of a mixture of butyl alcohol and 2 N acetic acid (95:5).
Developing solvent system— Prepare a mixture of butyl alcohol, glacial acetic acid, and water (60:20:20).
Procedure— Proceed as directed for Thin-Layer Chromatography under Chromatography 621. After air-drying the plate, spray with Spray reagent, and heat between 100 and 105 for about 15 minutes. Examine the plate under white light. The chromatogram obtained from the System suitability solution exhibits two clearly separated spots. Any secondary spot in the chromatogram obtained from the Test solution is not larger or more intense than the principal spot in the chromatogram obtained from the Standard solution: not more than 0.5% of any individual impurity is found; and not more than 2.0% of total impurities is found.
Organic volatile impurities, Method V 467: meets the requirements.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Assay— Transfer about 110 mg of Threonine, accurately weighed, to a 125-mL flask, dissolve in a mixture of 3 mL of formic acid and 50 mL of glacial acetic acid, and titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 11.91 mg of C4H9NO3.
Auxiliary Information— Staff Liaison : Lawrence Evans, III, Ph.D., Scientist
Expert Committee : (DSN05) Dietary Supplements - Non-Botanicals
USP29–NF24 Page 2138
Phone Number : 1-301-816-8389