Cysteine Hydrochloride
(sis' te een hye'' droe klor' ide).
C3H7NO2S·HCl 157.62 l-Cysteine hydrochloride monohydrate [7048-04-6]. Anhydrous [52-89-1]. DEFINITION
Cysteine Hydrochloride is l-cysteine hydrochloride monohydrate and contains NLT 98.5% and NMT 101.5% of l-cysteine hydrochloride (C3H7NO2S·HCl), calculated on the dried basis.
IDENTIFICATION
ASSAY
• Procedure
Sample:
250 mg of Cysteine Hydrochloride
Blank:
Proceed as directed in the Analysis without the Sample.
Titrimetric system
(See Titrimetry 541.)
Mode:
Residual titration
Titrant:
0.1 N iodine VS
Back titrant:
0.1 N sodium thiosulfate VS
Endpoint detection:
Visual
Analysis:
Transfer the Sample to an iodine flask. Add 20.0 mL of water and 4 g of potassium iodide, and mix. Cool the solution in an ice bath, and add 5 mL of 3 N hydrochloric acid and 25.0 mL of 0.1 N iodine VS. Insert the stopper, and allow to stand in the dark for 20 min. Titrate the excess iodine with the Back titrant. Add 3 mL of starch TS as the endpoint is approached. Perform the Blank determination. Calculate the percentage of cysteine hydrochloride (C3H7NO2S·HCl) in the Sample taken:
Result = {[(VB VS) × N × F]/W} × 100
Acceptance criteria:
98.5%101.5% on the dried basis
IMPURITIES
• Residue on Ignition 281:
NMT 0.4%
• Chloride and Sulfate, Sulfate 221
Standard solution:
0.10 mL of 0.020 N sulfuric acid
Sample:
0.33 g of Cysteine Hydrochloride
Acceptance criteria:
NMT 0.03%.
• Iron 241:
NMT 30 ppm
• Heavy Metals, Method I 231:
NMT 15 ppm
• Related Compounds
N-Ethylmaleimide solution:
40 mg/mL of N-ethylmaleimide in alcohol
Standard stock solution:
Dissolve 20 mg of USP l-Cysteine Hydrochloride RS in 10.0 mL of water. Add 10.0 mL of N-Ethylmaleimide solution, and mix. Allow the solution to stand for 5 min before using.
Standard solution:
0.05 mg/mL from Standard stock solution in water. [NoteThis solution has a concentration equivalent to 0.5% of that of the Sample solution. ]
System suitability solution:
Transfer 10 mg of USP l-Tyrosine RS and 10 mL of the Standard stock solution to a 25-mL volumetric flask. Dilute with water to volume.
Sample stock solution:
Transfer 0.2 g of Cysteine Hydrochloride to a 10-mL volumetric flask, dissolve, and dilute with water to volume.
Sample solution:
To 5.0 mL of the Sample stock solution add 5.0 mL of N-Ethylmaleimide solution, and mix. Allow the solution to stand for 5 min before using.
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.
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
Sample solution:
80 mg/mL in 6 N hydrochloric acid
Acceptance criteria:
+5.7 to +6.8
• Loss on Drying 731:
Dry a sample at room temperature at a pressure not exceeding 5 mm of mercury for 24 h: it loses 8.0%12.0% of its weight.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
Auxiliary Information
Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 2798
Pharmacopeial Forum: Volume No. 30(5) Page 1598
|