Phenylalanine
C9H11NO2 165.19
l-Phenylalanine
[63-91-2].
(fen'' il al' a neen).
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C9H11NO2 165.19
l-Phenylalanine
[63-91-2].DEFINITION
Phenylalanine contains NLT 98.5% and NMT 101.5% of l-phenylalanine (C9H11NO2), calculated on the dried basis.
IDENTIFICATION
ASSAY
• Procedure
Sample:
160 mg of Phenylalanine
Blank:
Mix 3 mL of formic acid and 50 mL of glacial acetic acid.
Titrimetric system
(See Titrimetry 
541
.)
541.)
Mode:
Direct titration
Titrant:
0.1 N perchloric acid VS
Endpoint detection:
Potentiometric
Analysis:
Dissolve the Sample in 3 mL of formic acid and 50 mL of glacial acetic acid. Titrate with the Titrant. Perform the Blank determination.
Calculate the percentage of phenylalanine (C9H11NO2) in the Sample taken:
Result = {[(VS 
VB) × N × F]/W} × 100
VB) × N × F]/W} × 100| VS | = | = Titrant volume consumed by the Sample (mL) |
| VB | = | = Titrant volume consumed by the Blank (mL) |
| N | = | = actual normality of the Titrant (mEq/mL) |
| F | = | = equivalency factor, 165.2 mg/mEq |
| W | = | = Sample weight (mg) |
Acceptance criteria:
98.5%–101.5% on the dried basis
IMPURITIES
• Residue on Ignition 281:
NMT 0.4%
281:
NMT 0.4%
• Chloride and Sulfate, Chloride 221
221
Standard solution:
0.50 mL of 0.020 N hydrochloric acid
Sample:
0.73 g of Phenylalanine
Acceptance criteria:
NMT 0.05%
• Chloride and Sulfate, Sulfate 221
221
Standard solution:
0.10 mL of 0.020 N sulfuric acid
Sample:
0.33 g of Phenylalanine
Acceptance criteria:
NMT 0.03%
• Iron 241:
NMT 30 ppm
241:
NMT 30 ppm
• Heavy Metals, Method I 231:
NMT 15 ppm
231:
NMT 15 ppm
• Related Compounds
Diluent:
Glacial acetic acid and water (1:1)
Standard solution:
0.05 mg/mL of USP l-Phenylalanine RS in Diluent. [Note—This solution has a concentration equivalent to 0.5% of that of the Sample solution. ]
System suitability solution:
0.4 mg/mL each of USP l-Phenylalanine RS and USP l-Tyrosine RS in Diluent
Sample solution:
10 mg/mL of Phenylalanine in Diluent
Chromatographic system
Mode:
TLC
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture
Application volume:
5 µL
Developing solvent system:
Butyl alcohol, glacial acetic acid, and water (3:1:1)
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:
Standard solution, System suitability solution, and Sample solution
After air-drying the plate, spray with Spray reagent, and heat between 100
and 105 for 15 min. Examine the plate under white light.
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.
Individual impurities:
NMT 0.5%
Total impurities:
NMT 2.0%
SPECIFIC TESTS
• Optical Rotation, Specific Rotation 781S
781S
Sample solution:
20 mg/mL in water
Acceptance criteria:
32.7 to 34.7
32.7 to 34.7
• Loss on Drying 731:
Dry a sample at 105 for 3 h: it loses NMT 0.3% of its weight.
731:
Dry a sample at 105 for 3 h: it loses NMT 0.3% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Huy T. Dinh, M.S.
Scientific Liaison 1-301-816-8594 |
(DS2010) Monographs - Dietary Supplements |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 4296