LINEAR ALKYLBENZENE SULFONATE (LAS) - UNEP Chemicals

OECD SIDS LINEAR ALKYLBENZENE SULFONATE (LAS)
vessels sealed with a rubber septum, the solution purged with argon and a
fixed volume of oxygen injected. Spectrophotometric analysis was
performed at regular intervals.
GLP: Yes [ ] No [ ] ? [X]
Test substance: LAS (CAS #25155-30-0)
Remarks: The reaction involves fast decomposition of the aromatic ring followed by
slower oxidation of the aliphatic chain.
Reference: Hidaka, H., Kubata, H., Gratzel, M., Serpone, N. and Pelizzetti, E. 1985.
Photodegradation of surfactants. I. Degradation of sodium dodecyl sulfonate
in aqueous semiconductor dispersions. Nouveau J. Chemie 9:67-69.
Reliability: 2 Valid with restrictions
(c)
Type: Air [ ]; Water [X]; Soil [ ]; Other [ ]
Light source: Sunlight [ ]; Xenon lamp [ ]; Other [X] Mercury lamp
Light spectrum: 400-580 nm
Spectrum: 223 nm
Concentration: 100 mg/L H20
Temperature: 20°C
Indirect Photolysis:
Type of sensitizer: Humic substances
Results: Photodegradation of LAS was reduced by humic substances by a factor of 2
or more. The aliphatic side chains are degraded first, followed by aromatic
ring cleavages. Degradation follows first order kinetics both with and
without the presence of humics.
Method: The effects of humics on the photolytic degradation of LAS was studied.
Soil humic substances were extracted by a cationic exchange resin/water
suspension from a humic podzol. Water-soluble synthetic humic substances
were prepared by autoxidation of pyrogallol in alkaline solution. Aqueous
solutions of 15 mg/L humic substance and 100 mg/L LAS were irradiated
with a mercury lamp. Photometric measurements were performed with a
spectrophotometer for recording the changes caused by photolysis at definite
times at 223 nm for LAS.
GLP: Yes [ ] No [ ] ? [X]
Test substance: LAS (CAS #25155-30-0)
Remarks: The presence of humic substances delays photodegradation of LAS,
primarily because they act as UV-absorbers. The reaction between humics
and LAS is dominated by electrostatic repulsion because of the negatively
charged components at the given pH. The hydrophobic interaction between
humics and LAS is relatively weak compared to the electrostatic repulsion.
Possibly the sulfonic groups from LAS may be bound by metal bridges to
humic surfaces. The study used humic substance with a relatively high
proportion of aromatic carbon; whereas a lower proportion is more typical in
natural environments. Therefore, the difference in photolysis rate is likely to
be less pronounced.
Reference: Hermann, R., Gerke, J. and Ziechmann, W. 1997. Photodegradation of the
surfactants LAS and dodecylpyridinium-chloride as affected by humic
substances. Water, Air, and Soil Pollution 98:45-55.
Reliability: 2 Valid with restrictions
3.1.2 STABILITY IN WATER
Type: Abiotic (hydrolysis) [X] ; biotic (sediment)[ ]
Results: LAS is stable in water.
GLP: Yes [ ] No [X] ? [ ]
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