Sodium Lauryl Sulfate
Sulfuric acid monododecyl ester sodium salt;
Sodium monododecyl sulfate
[151-21-3].
(soe' dee um lawr' il sul' fate).
Sulfuric acid monododecyl ester sodium salt;
Sodium monododecyl sulfate
[151-21-3].DEFINITION
Sodium Lauryl Sulfate is a mixture of sodium alkyl sulfates consisting chiefly of sodium lauryl sulfate [CH3(CH2)10CH2OSO3Na]. The combined content of sodium chloride and sodium sulfate is NMT 8.0%.
IDENTIFICATION
• A. Identification Tests—General, Sodium 
191
:
Ignite 500 mg at 800
until the carbon is consumed. The residue dissolved in 10 mL of water meets the requirements.
191:
Ignite 500 mg at 800 until the carbon is consumed. The residue dissolved in 10 mL of water meets the requirements.
• B. Identification Tests—General, Sulfate 191:
A solution (1 in 10), after acidification with hydrochloric acid and gentle boiling for 20 min, meets the requirements.
191:
A solution (1 in 10), after acidification with hydrochloric acid and gentle boiling for 20 min, meets the requirements.
IMPURITIES
Inorganic Impurities
• Heavy Metals, Method II 231:
20 ppm
231:
20 ppm
• Sodium Chloride
Sample solution:
100 mg/mL in water
Analysis:
Neutralize 50 mL of Sample solution with 0.8 N nitric acid, using litmus paper as the indicator. Add 2 mL of potassium chromate TS, and titrate with 0.1 N silver nitrate VS. Each mL of 0.1 N silver nitrate is equivalent to 5.844 mg of NaCl.
SPECIFIC TESTS
• Sodium Sulfate
Lead nitrate solution:
33.1 g/L of lead nitrate in water
Analysis:
Transfer 1 g of Sodium Lauryl Sulfate, weighed, to a 250-mL beaker. Add 35 mL of water, and warm to dissolve. To the warm solution add 2.0 mL of 1 N nitric acid, mix, and add 50 mL of alcohol. Heat the solution to boiling, and slowly add 10 mL of Lead nitrate solution, with stirring. Cover the beaker, simmer for 5 min, and allow to settle. If the supernatant is hazy, allow to stand for 10 min, heat to boiling, and allow to settle. When the solution is almost to the boiling point, decant as much liquid as possible through 9-cm filter paper (Whatman No. 41 or equivalent). Wash four times by decantation, each time using 50 mL of 50% alcohol, and bring the mixture to a boil. Transfer the filter paper to the original beaker, and immediately add 30 mL of water, 20.0 mL of 0.05 M edetate disodium VS, and 1 mL of ammonia–ammonium chloride buffer TS. Warm to dissolve the precipitate, add 0.2 mL of eriochrome black TS, and titrate with 0.05 M zinc sulfate VS. Each mL of 0.05 M edetate disodium is equivalent to 7.102 mg of Na2SO4.
Acceptance criteria:
NMT 8.0% of the combined content of sodium chloride and sodium sulfate
• Alkalinity
Sample solution:
Dissolve 1.0 g in 100 mL of water, add phenol red TS, and titrate with 0.10 N hydrochloric acid.
Acceptance criteria:
NMT 0.60 mL for neutralization
• Total Alcohols:
Transfer 5 g to an 800-mL Kjeldahl flask, and add 150 mL of water, 50 mL of hydrochloric acid, and a few boiling chips. Attach a reflux condenser to the Kjeldahl flask, heat carefully to avoid excessive frothing, and boil for 4 h. Cool the flask, rinse the condenser with ether, collecting the ether in the flask, and transfer the contents to a 500-mL separator, rinsing the flask twice with ether and adding the washings to the separator. Extract the solution with two 75-mL portions of ether, evaporate the combined ether extracts in a tared beaker on a steam bath, dry the residue at 105 for 30 min, cool, and weigh.
for 30 min, cool, and weigh.
Acceptance criteria:
The residue represents the total alcohols and is NLT 59.0% of the weight of Sodium Lauryl Sulfate taken.
• Unsulfated Alcohols
Sample solution:
Dissolve 10 g in 100 mL of water, and add 100 mL of alcohol.
Analysis:
Transfer the solution to a separator, and extract with three 50-mL portions of solvent hexane. If an emulsion forms, sodium chloride may be added to promote separation of the two layers. Wash the combined solvent hexane extracts with three 50-mL portions of water, and dry with anhydrous sodium sulfate. Filter the solvent hexane extract into a tared beaker, evaporate on a steam bath until the odor of solvent hexane no longer is perceptible, dry the residue at 105 for 30 min, cool, and weigh.
for 30 min, cool, and weigh.
Acceptance criteria:
The weight of the residue is NMT 4.0% of the weight of Sodium Lauryl Sulfate taken.
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Robert H. Lafaver, M.S.
Scientific Liaison 1-301-816-8335 |
(EXC2010) Monographs - Excipients |
USP35–NF30 Page 1956