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Surface tension

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Reference
Endpoint:
surface tension
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

To address the endpoint surface tension for the target substance Reaction mass of sodium octane-1-sulfonate and disodium octane 1,2-disulfonate, data on the two main constituents octyl sulfonate and octyl disulfonate are taken combined to draw an overall conclusion on the surface activity of the target substance Reaction mass of sodium octane-1-sulfonate and disodium octane 1,2-disulfonate. The surface-active properties of the constituents with two sulfonic groups differ to a certain degree from their monosulfonate counterparts, because they have a more polar head, while the length of the hydrophobic tail (octyl) is the same. Thus, their water solubility, adsorption and absorption potentials and concentrations for an optimal micelle formation could be different. To account for these differences data on both, octyl sulfonate and octyl disulfonate are regarded.
The target substance contains some impurities. Their influence is discussed in the following:
The impurity ethylhexyl sulfonate has a branched chemical structure, which also fulfils criteria of a surfactant because it has terminal position of the sulfonate group and the hydrophobic ethylhexyl moiety. All other sulfonate containing impurities are isomers either of octyl sulfonate, or octyl disulfonate. Their sulfonate groups are situated at different carbons of the octyl moiety and therefore they possess either weaker surfactant properties, or do not possess them at all.
Sodium sulfate is an impurity due to production process and is contained in all products of the PAS subcategory and ANS category (SIDS, 2007).
Minor amounts of benzoic acid are considered not to impact the prediction, because it is a substance of low intrinsic toxicity (SIDS, 2001; SCCP, 2005). The presence of minor amounts of alcohols is also typical for the members of the PAS subcategory (SIDS, 2007). Benzoic acid and tert-butyl alcohol are reported to be decomposed products of the t-butyl peroxy benzoate that was used as catalyst (Akzo Nobel, 2016). Another impurity is sulfate, which is not expected to influence the surface activity of the target substance Reaction mass of sodium octane-1-sulfonate and disodium octane 1,2-disulfonate.

All in all, based on this information, it is scientifically justified to use data on the two main constituents octyl sulfonate and octyl disulfonate to address the endpoint surface tension for the target substance Reaction mass of sodium octane-1-sulfonate and disodium octane 1,2-disulfonate.


Reason / purpose:
read-across source
Reason / purpose:
read-across source
Key result
Surface tension:
30.5 mN/m
Conc.:
23.14 g/L
Remarks on result:
other: no temperature stated
Key result
Surface tension:
30 mN/m
Conc.:
105.43 g/L
Remarks on result:
other: no temperature stated
Conclusions:
Surface tension of the sample was determined to be 30.5 mN/m for the 1-sulphonate and 30.0 mN/m for the 1,2-sulphonate. This values were determined both at the critical micelle concentration which is different for each sample (1-sulphonate: 23.14 g/L & 1,2-sulphonate: 105.43 g/L).
So for the target-substance surface tension of 30.25 mN/m (arithmetic mean) at the critical micelle concentration is predicted.
Executive summary:

Surface tension of the sample was determined according to ASTM D-1331 using a Cahn RG electrobalance" Cerritos, CA, in conjunction with a Varian model 9176 recorder, Palo Alto, CA, instead of a quartz torsion balance to be 30.5 mN/m for the 1 -sulphonate and 30.0 mN/m for the 1,2 -sulphonate. This values were determined both at the critical micelle concentration which is different for each sample (1-sulphonate: 23.14 g/L & 1,2-sulphonate: 105.43 g/L).

So for the target-substance surface tension of 30.25 mN/m (arithmetic mean) at the critical micelle concentration is predicted.

Description of key information

Surface tension of the sample was determined according to ASTM D-1331 using a Cahn RG electrobalance" Cerritos, CA, in conjunction with a Varian model 9176 recorder, Palo Alto, CA, instead of a quartz torsion balance to be 30.5 mN/m for the 1 -sulphonate and 30.0 mN/m for the 1,2 -sulphonate. This values were determined both at the critical micelle concentration which is different for each sample (1-sulphonate: 23.14 g/L & 1,2-sulphonate: 105.43 g/L).

So for the target-substance surface tension of 30.25 mN/m (arithmetic mean) at the critical micelle concentration is predicted.

Key value for chemical safety assessment

Surface tension:
30.25

Additional information

No temperature was stated, but it could be assumed, that based on the guideline-procedure standard-conditions (20 °C) were used to perfom the surface-tension study.

No concentration stated for CSA because the key value for the sample based on read-across from the two main constituents of this test item. For this the arithmetic mean was calculated because the two values are quite similar and both measured at the critical micelle concentration. Unfortunately this critical micelle concentration is, based on the structure (one sulphate group vs two sulphate groups), different for each constituent. But, nevertheless it is possible to predict the surface tension of the test-item because basis is the critical micelle concentration. So at the critical micelle concentration (which is not known for the sample) the surface tension is 30.25 mN/m based on the results of the two main constituents.