Tyrosine
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This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
C9H11NO3 181.19
L-Tyrosine CAS RN: 60-18-4; UNII: 42HK56048U.
1 DEFINITION
Tyrosine contains NLT 98.5% and NMT 101.5% of l-tyrosine (C9H11NO3), calculated on the dried basis.
2 IDENTIFICATION
A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K
3 ASSAY
Procedure
Sample: 180 mg of Tyrosine
Blank: Mix 6 mL of formic acid and 50 mL of glacial acetic acid.
Titrimetric system
(See Titrimetry 〈541〉.)
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
4 IMPURITIES
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%
Change to read:
A IRON (241), Procedures, Procedure 1A (CN 1-JUN-2023): NMT 30 ppm. [NOTE-If necessary, use 2 mL of hydrochloric acid to dissolve the Sample.]
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
(See Chromatography (621), Thin-Layer Chromatography.)
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.
Analysis
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%
5 SPECIFIC TESTS
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.
6 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in well-closed containers.
USP Reference Standards 〈11〉
USP l-Phenylalanine RS
USP l-Tyrosine RS
