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Sodium lauryl sulfate (SLS) is a widely used anionic surfactant characterized by a 12-carbon hydrophobic tail and a sulfate polar head.
It is used globally in detergents, personal care products, industrial cleaning formulations, laboratory reagents (notably SDS for protein denaturation and electrophoresis), and certain food and pharmaceutical applications under regulated limits.
Its physicochemical properties (critical micelle concentration, surface tension lowering, foaming) make it highly effective as a wetting and emulsifying agent.
Preferred name: Sodium lauryl sulfate (IUPAC: sodium dodecyl sulfate)
CAS Registry Number: 151-21-3
Chemistry and molecular structure
1.1 Chemical class and amphiphilicity
SLS is an anionic organosulfate surfactant: a hydrophobic alkyl chain (C12) attached to a hydrophilic sulfate head (–OSO₃⁻) with sodium as counterion.
This amphiphilic structure gives it strong surface-active properties: it reduces surface and interfacial tension, promotes micelle formation above a characteristic concentration (CMC), and acts as a detergent, emulsifier, and foaming agent.
Structure and isomers
The classical “SLS” molecule is sodium dodecyl sulfate whose chain can be linear (n-dodecyl). Commercial SLS derived from fats/oils may contain a distribution of chain lengths (C10–C14), branching impurities, and residual alcohols; such mixtures are often marketed as sodium coco sulfate (SCS) when obtained from coconut-derived fatty alcohols.
The sulfate head is covalently bonded to the alkyl oxy group (alkyl sulfate, not alkyl sulfonate).
Physicochemical constants (typical)
Molecular weight: ~288.4 g·mol⁻¹.
Critical micelle concentration (CMC): ~8 mM at 25 °C (value depends on purity, counterion, ionic strength, and temperature).
Solubility: Highly soluble in water (forms clear to slightly hazy solutions depending on concentration and purity); poorly soluble in nonpolar organic solvents.
Melting point / decomposition: Technical grades have varying melting/softening ranges; pure SDS decomposes/char at elevated temperatures; typical solid appearance is waxy/crumbly.
Surface tension reduction: SLS rapidly decreases water surface tension (relative performance varies with concentration vs. other surfactants).
Industrial production routes
Sulfation of lauryl (dodecyl) alcohol
The predominant industrial method is sulfation of fatty alcohol (lauryl alcohol or mixed C10–C14 alcohols) using chlorosulfonic acid or sulfur trioxide (SO₃) (or oleum-based sulfating reagents) to give the alkyl sulfate half-ester, followed by neutralization with sodium hydroxide to produce the sodium salt.
When SO₃ is used in controlled gas-phase or complexing processes, yields and byproducts vary; neutralization must be controlled to avoid over-salting and to manage heat.
The method yields alkyl sulfates that may then be diluted, dried, or formulated.
Other routes and mixture products
Sulfonation routes (less common for pure alkyl sulfate).
Manufacture from natural feedstocks: lauryl alcohol is derived from coconut oil or palm kernel oil fractions; when mixed fatty alcohol feedstock is used the finished product is a mixture (sodium coco sulfate) rather than pure SDS, affecting properties.
Industrial forms & grades
Technical solid (powder/flakes): commonly used in detergents and laboratories.
Liquid concentrates (25–70% w/w): easier handling for liquid detergents and emulsions.
Food/Pharmacopoeial grades (FCC, NF, Ph. Eur. specifications) for defined food/processing uses.
Analytical methods and quality control
Typical assays and specification tests
Titration for active matter (%) (acid-base titration after hydrolysis).
Ion chromatography for residual sulfate, counterion analysis.
Gas chromatography (GC) (after appropriate derivatization) or HPLC for chain-length distribution and impurities.
FT-IR and NMR for structural confirmation.
Mass spectrometry (MS) for exact mass/confirmation.
Surface tension and foaming tests; CMC determination for functional performance.
Producers and QC laboratories use certificate of analysis outputs to report active matter, moisture, pH, and sulfur content.
Impurity profiling
Impurities include unreacted alcohol, sulfation byproducts, residual inorganic salts, shorter/longer alkyl homologues, and traces of chlorinated species (if chlorosulfonic acid was used).
Commercial suppliers supply COAs and MSDS specifying permitted impurity ranges.
Physicochemical behavior and mechanisms
Micellization and solution behavior
Above the CMC, SLS molecules self-assemble into micelles; micellization is influenced by ionic strength, temperature, and presence of cosolvents.
SLS forms spherical or oblate micelles at low concentrations, and with increasing concentration and ionic strength may form rodlike or more complex structures.
Counterion binding (Na⁺) and addition of electrolytes reduce the CMC and change micelle morphology.
Interactions with proteins and lipids
SLS strongly interacts with proteins: it binds to polypeptide chains (roughly 1 SDS per 2 amino acid residues) and denatures proteins by disrupting noncovalent interactions and imparting a uniform negative charge—this property underpins SDS-PAGE electrophoresis for molecular mass separation. It also solubilizes membrane lipids and disrupts lipid bilayers at sufficient concentrations, which explains efficacy as a detergent and its potential to irritate biological membranes.
Surface activity: wetting, foaming, emulsification
SLS lowers surface tension and increases wettability; its foaming ability is high (beneficial for certain formulations but not all), and it helps form oil-in-water emulsions when combined with co-surfactants and appropriate formulation stabilizers.
Applications
Personal care and household products
Toothpastes, shampoos, body washes, soaps, and liquid cleansers: SLS is used for foaming, cleansing, and emulsifying.
Concentrations in rinse-off products typically range from ~0.5% to several percent depending on product type.
Shaving creams and bubble baths: leveraged for foaming and lubrication.
Cosmetic formulations: used with mildness enhancers or replaced by milder surfactants where irritation is a concern.
Industrial cleaning and textiles
Used in degreasers, floor cleaners, and textile processing for wetting and soil removal.
Laboratory and biochemical uses
Biochemistry: SDS (SLS) is fundamental to protein extraction, solubilization, SDS-PAGE electrophoresis (denaturing gels), and nucleic acid purifications (lysis buffers).
At laboratory grade (>95%) it’s sold specifically as SDS for research.
Pharmaceutical and food uses (regulated)
Pharmacopeial and food uses: Certain grades permitted in food contact or processing under strict limits (e.g., limited uses such as egg white processing; see USP/FCC/Ph. Eur. monographs for details). Use and maximum concentrations are regulated.
Niche applications
Nanomaterial dispersions: widely used to disperse carbon nanotubes and other hydrophobic particulates in aqueous media.
Microbicidal research: in vitro evidence of virus inactivation (membrane disruption), though use as microbicide in humans is constrained by safety and formulation issues.
SAFETY INFORMATION ABOUT SODIUM LAURYL SULPHATE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
