(tye' roe seen).
Click to View Image
Click to View USP ImageClick to View 3D Image

l-Tyrosine    [60-18-4].
Tyrosine contains NLT 98.5% and NMT 101.5% of l-tyrosine (C9H11NO3), calculated on the dried basis.
•  Procedure
Sample: 180 mg of Tyrosine
Blank: Mix 6 mL of formic acid and 50 mL of glacial acetic acid.
Titrimetric system 
Mode: Direct titration
Titrant: 0.1 N perchloric acid VS
Endpoint detection: Potentiometric
Analysis: Dissolve the Sample in 6 mL of formic acid and 50 mL of glacial acetic acid, and titrate with the Titrant. Perform the Blank determination.
Calculate the percentage of tyrosine (C9H11NO3) in the Sample taken:
Result = {[(VS VB) × N × F]/W} × 100
VS== volume of Titrant consumed by the Sample (mL)
VB== volume of Titrant consumed by the Blank (mL)
N== actual normality of the Titrant (mEq/mL)
F== equivalency factor, 181.2 mg/mEq
W== Sample weight (mg)
Acceptance criteria: 98.5%–101.5% on the dried basis
•  Residue on Ignition 281: NMT 0.4%
•  Chloride and Sulfate, Chloride 221
Standard solution: 0.20 mL of 0.020 N hydrochloric acid
Sample: 0.35 g of Tyrosine. [Note—If necessary, dissolve the Sample by heating to near boiling and adding 1 mL of nitric acid. ]
Acceptance criteria: NMT 0.04%
•  Chloride and Sulfate, Sulfate 221
Standard solution: 0.50 mL of 0.020 N sulfuric acid
Sample: 1.2 g of Tyrosine. [Note—If necessary, dissolve the Sample by adding 6 mL of diluted hydrochloric acid. ]
Acceptance criteria: NMT 0.04%
•  Iron 241: NMT 30 ppm. [Note—If necessary, use 2 mL of hydrochloric acid to dissolve the Sample. ]
•  Heavy Metals, Method I 231: NMT 15 ppm
•  Related Compounds
Diluted ammonia solution: Dilute 16 mL of concentrated ammonia with water to 100 mL.
System suitability solution: Dissolve 10 mg of USP l-Tyrosine RS and 10 mg of USP l-Phenylalanine RS in 1 mL of Diluted ammonia solution, and dilute with water to 25.0 mL.
Standard solution: In a suitable flask, dissolve a quantity of USP l-Tyrosine RS in 1 mL of Diluted ammonia solution. Dilute with water to volume to obtain a solution of 0.05 mg/mL. [Note—This solution has a concentration equivalent to 0.5% of that of the Sample solution. ]
Sample solution: Transfer 0.1 g of Tyrosine into a 10-mL volumetric flask, add sufficient Diluted ammonia solution to dissolve, and dilute with water to volume.
Chromatographic system 
Mode: TLC
Adsorbent: 0.25-mm layer of chromatographic silica gel mixture
Application volume: 5 µL
Developing solvent system: Isopropyl alcohol and ammonium hydroxide (7:3)
Spray reagent: 2 mg/mL of ninhydrin in a mixture of butyl alcohol and 2 N acetic acid (95:5)
System suitability 
Suitability requirements: The chromatogram of the System suitability solution exhibits two clearly separated spots.
Samples: System suitability solution, Standard solution, and Sample solution
Dry the plate between 100 and 105 until the ammonia disappears completely. Spray with Spray reagent, and heat between 100 and 105 for 15 min. Examine the plate under white light.
Acceptance criteria: Any secondary spot of the Sample solution is not larger or more intense than the principal spot of the Standard solution.
Any individual impurity: NMT 0.5%
Total impurities: NMT 2.0%
•  Optical Rotation, Specific Rotation 781S
Sample solution: 50 mg/mL in 1 N hydrochloric acid
Acceptance criteria: 9.8 to 11.2
•  Loss on Drying 731: Dry a sample at 105 for 3 h: it loses NMT 0.3% of its weight.
•  Packaging and Storage: Preserve in well-closed containers.
•  USP Reference Standards 11
USP l-Phenylalanine RS Click to View Structure
USP l-Tyrosine RS Click to View Structure
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/QuestionContactExpert Committee
MonographHuy T. Dinh, M.S.
Scientific Liaison
(DS2010) Monographs - Dietary Supplements
Reference StandardsRS Technical Services
USP35–NF30 Page 4976
Pharmacopeial Forum: Volume No. 32(6) Page 1761
Chromatographic Column— 
Chromatographic columns text is not derived from, and not part of, USP 35 or NF 30.