Acetylcysteine
C5H9NO3S 163.20
l-Cysteine, N-acetyl-;
N-Acetyl-l-cysteine
[616-91-1].
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C5H9NO3S 163.20
l-Cysteine, N-acetyl-;
N-Acetyl-l-cysteine
[616-91-1].DEFINITION
Acetylcysteine contains NLT 98.0% and NMT 102.0% of C5H9NO3S, calculated on the dried basis.
IDENTIFICATION
ASSAY
• Procedure
Mobile phase:
6.8 g/L of monobasic potassium phosphate. Adjust with phosphoric acid to a pH of 3.0.
Sodium metabisulfite solution:
0.5 mg/mL of sodium metabisulfite in water, freshly prepared
Internal standard solution:
5 mg/mL of USP l-Phenylalanine RS in Sodium metabisulfite solution
Standard stock solution:
10 mg/mL of USP Acetylcysteine RS in Sodium metabisulfite solution
Standard solution:
0.5 mg/mL of USP Acetylcysteine RS and 0.25 mg/mL of USP l-Phenylalanine RS in Sodium metabisulfite solution from Standard stock solution and Internal standard solution
Sample stock solution:
10 mg/mL of Acetylcysteine in Sodium metabisulfite solution
Sample solution:
0.5 mg/mL of Acetylcysteine and 0.25 mg/mL of USP l-Phenylalanine RS in Sodium metabisulfite solution from Sample stock solution and Internal standard solution
Chromatographic system
Mode:
LC
Detector:
UV 214 nm
Column:
3.9-mm × 30-cm; packing L1
Flow rate:
1.5 mL/min
Injection size:
5 µL
System suitability
Sample:
Standard solution
[Note—The relative retention times for acetylcysteine and l-phenylalanine are about 0.5 and 1.0, respectively. ]
Suitability requirements
Resolution:
NLT 6 between acetylcysteine and l-phenylalanine
Relative standard deviation:
NMT 2.0%
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of acetylcysteine (C5H9NO3S) in the portion of Acetylcysteine taken:
Result = (RU/RS) × (CS/CU) × 100
| RU | = | = peak response ratio of acetylcysteine to l-phenylalanine from the Sample solution |
| RS | = | = peak response ratio of acetylcysteine to l-phenylalanine from the Standard solution |
| CS | = | = concentration of USP Acetylcysteine RS in the Standard solution (mg/mL) |
| CU | = | = concentration of acetylcysteine in the Sample solution (mg/mL) |
Acceptance criteria:
98.0%–102.0% on the dried basis
IMPURITIES
• Residue on Ignition 
281
:
NMT 0.5%
281:
NMT 0.5%
• Heavy Metals, Method II 231
231
[Caution—Exercise care because explosion may occur.
]
Analysis:
In a dropwise manner, wet the sample with 2 mL of nitric acid, and proceed as directed for the Test preparation.
Acceptance criteria:
NMT 10 ppm
SPECIFIC TESTS
• Optical Rotation, Specific Rotation 781S
781S
Buffer:
Mix 29.5 mL of 1 N sodium hydroxide, 50 mL of 1 M monobasic potassium phosphate, and sufficient water to make 100 mL. Adjust to a pH of 7.0 ± 0.1 by adding more of either solution, as necessary.
Sample solution:
In a 25-mL volumetric flask, mix 1.25 g with 1 mL of edetate disodium solution (1 in 100), add 7.5 mL of sodium hydroxide solution (1 in 25), and mix to dissolve. Dilute with Buffer to volume.
Acceptance criteria:
+21
to +27
to +27
• pH 791:
2.0–2.8 in a solution (1 in 100)
791:
2.0–2.8 in a solution (1 in 100)
• Loss on Drying 731:
Dry a sample at a pressure of about 50 mm of mercury at 70 for 4 h: it loses NMT 1.0% of its weight.
731:
Dry a sample at a pressure of about 50 mm of mercury at 70 for 4 h: it loses NMT 1.0% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers, and store at controlled room temperature.
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Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Clydewyn M. Anthony, Ph.D.
Senior Scientific Liaison 1-301-816-8139 |
(SM22010) Monographs - Small Molecules 2 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 2069
Pharmacopeial Forum: Volume No. 31(3) Page 726