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C9H11NO3 181.19

l-Tyrosine [60-18-4].
» Tyrosine contains not less than 98.5 percent and not more than 101.5 percent of C9H11NO3, as l-tyrosine, calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Specific rotation 781S: between 9.8 and 11.2.
Test solution: 50 mg per mL, in 1 N hydrochloric acid.
Loss on drying 731 Dry it at 105 for 3 hours: it loses not more than 0.3% of its weight.
Residue on ignition 281: not more than 0.4%.
Chloride 221 A solution containing 0.35 g shows no more chloride than corresponds to 0.20 mL of 0.020 N hydrochloric acid (0.04%). [note—If necessary, dissolve the test specimen by heating to near boiling and adding 1 mL of nitric acid.]
Sulfate 221 A solution containing 1.2 g shows no more sulfate than corresponds to 0.50 mL of 0.020 N sulfuric acid (0.04%). [note—If necessary, dissolve the test specimen by adding 6 mL of diluted hydrochloric acid.]
Iron 241: 0.003%. [note—If necessary, use 2 mL of hydrochloric acid to dissolve the test specimen.]
Chromatographic purity—
Adsorbent: 0.25-mm layer of chromatographic silica gel mixture.
Diluted ammonia solution— Transfer 16 mL of concentrated ammonia to a 100-mL volumetric flask, and dilute with water to volume.
Test solution— Transfer about 0.1 g of Tyrosine, accurately weighed, to a 10-mL volumetric flask, dissolve in Diluted ammonia solution, and dilute with water to volume. Apply 5 µL.
Standard solution— In a suitable flask, dissolve an accurately weighed quantity of USP l-Tyrosine RS in 1 mL of Diluted ammonia solution, and dilute with water to volume 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— Dissolve about 10 mg of USP l-Tyrosine RS and about 10 mg of USP l-Phenylalanine RS in 1 mL of Diluted ammonia solution, dilute with water to 25.0 mL, and mix. 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 isopropyl alcohol and ammonium hydroxide (70:30).
Procedure— Proceed as directed for Thin-Layer Chromatography under Chromatography 621. Dry the plate between 100 and 105 until the ammonia disappears completely. 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.
Assay— Transfer about 180 mg of Tyrosine, accurately weighed, to a 125-mL flask, dissolve in 6 mL of formic acid, add 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 18.12 mg of C9H11NO3.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Curtis Phinney

(DSN05) Dietary Supplements - Non-Botanicals
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 3829
Pharmacopeial Forum: Volume No. 32(6) Page 1761
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.