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Description of key information

GLP Study according to EU Method A.5 (Wilhelmy plate).
General Phsysical Chemistry, Schering AG, Berlin, Study report NC58EY10 (APC (85/99), dated 1999-11-24.
Hydroxydrospirenon is considered to be surface active according to the items given in guideline A.5.

Key value for chemical safety assessment

Surface tension:
54.5
in mN/m at 20°C and concentration in mg/L:
86

Additional information

Methods:

A suspension made by dissolving an excess of the test substance in water was equilibrated in a thermostated water bath while stirring at 20 °C for 3 days. After equilibration the suspension was filled in centrifuge tubes for centrifugation (two times for 30 min at 30000 g) for separation of undissolved substance from aqueous solution using a ultracentrifuge with temperature control. The temperature during centrifugation was kept constant at 20 °C by appropriate cooling of the rotor casing.

45 mL samples were taken with a syringe and diluted to 50 mL with water (90 % of the saturated solution).

The concentration of Hydroxydrospirenone in the test solution was determined by HPLC before and after the experiments.

The surface tension of the aqueous solutions containing approx. 86 mg/L Hydroxydrospirenone was measured according to the EC Guideline A.5 and the user manual K122 (Krüss GmbH) using a Wilhelmy plate at 20 °C ± 0.1 °C. The measurements were made over a period of 20s in 2s intervals.

The validity of the procedure was proved by a calibration of the instrument with water bidest.

Results:

-       The mean value of the surface tension at 20°C (with the 95% confidence intervals) from the last 5 measurements of two experiment each (10 measurements) was 54.51± 0.48 mN/m.

-       No time dependence of the surface tension was observed during the experimental time.

-       The stability of the substance in the test solution was checked by HPLC. No change was observed during a period of 8 hours.

-       According to the items given in the EC Guideline A.5, Hydroxydrospirenone is considered to be surface active.