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Physical & Chemical properties

Surface tension

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Endpoint:
surface tension
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because surface activity is not a desired property of the material
Endpoint:
surface tension
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source substance is the racemic form of the target substance d-tetramethrin. Tetramethrin does consist of 50% d- and l-form, and both do exist as cis and trans isomers. Hence, the target substance does consist of d-cis-tetramethrin, d-trans-tetramethrin, l-cis-tetramethrin and l-trans-tetramethrin, whereas the target substance only contains the first two (i.e. d-cis-tetramethrin, d-trans-tetramethrin).
Both, the source as well as the target substance, do have a cis/trans ratio of approximately 1/4 and obviously do share same molecular mass and other properties. Thus, the source substance by definition does contain 50% of the d-form and the l-form is not expected to be significantly different with respect to its surface tension, having been determined in a GLP compliant guideline study to be 55.3 mN/m at 20 °C.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The d-tetramethrin with a purity > 80 % does contain its corresponding l-form as an impurity in the range of < 7%, other impurities from the manufacturing process are individually below 1% (w/w) each. The source substance that has been tested was having a purity of approx. 98% as tetramethrin with a cis/trans ratio of 1/4 and a d-form/l-form ratio of ~50/50.
3. ANALOGUE APPROACH JUSTIFICATION
Source and Target substance do share identical structure and molecular weight, only differentiating by the fact that the source substance is a racemic mixture, whereas the target substance represents almost pure d-form. Thus, physico-chemical parameters, not being affected significantly by stereochemistry, are fully comparable, thus justifying using surface tension data on the racemic form for read-across to the d-enantiomer.
4. DATA MATRIX
Composition comparison
D-tetramethrin (target) tetramethrin (source)
D-trans tetramethrin 70 - 80% 40 – 50%
D-cis tetramethrin 10 - 20% 7 – 11 %
L-trans tetramethrin 0 – 5% 35 – 40%
L-cis tetramethrin 0 – 2% 7 – 11%
Surface tension:
55.3 mN/m
Temp.:
20 °C
Conc.:
1.83 mg/L
Conclusions:
Although surface tenison is not a desired property of d-tetramethrin nor of racemic tetramethrin, it has been determined for the racemic form and found being 55.3 mN/m at 20 °C in a sturated solution (1.83 mg/L). The result is considered representative to the d-tetramethrin too, as surface activity is usually not influenced by stereochemical differences.

Description of key information

A study to determine surface tension is not required as surface activity is not a desired property of the material. Furthermore, data from the racemic mixture, tested as saturated solution (1.83 mg/L) are available showing a surface tension of 55.3 mN/m and thus being considered surface active according to interpretation as stated in method A.5 (<60 mN/m). Hence, this value is used for hazard and risk assessment.

Key value for chemical safety assessment

Surface tension:
55.3
in mN/m at 20°C and concentration in mg/L:
1.83

Additional information