Phenyl diamidophosphate

Water solubility

Description of key information

The water solubility of PPDA was determined according to OECD Guideline 105 as 5.60 ± 0.07 g/L at 20.0 ± 0.5 °C.

Key value for chemical safety assessment

Water solubility:

5.6 g/L

at the temperature of:

20 °C

Additional information

The solubility of the test item PPDA in water was determined by HPLC measurement according to OECD Guideline 105.

Based on the results of a preliminary test (solubility lies in the rangeof 1 – 10 g/L), the flask method was used for the determination of the solubility of the test item in accordance with the guideline.

In the main study, 50 – 100 g/L test item in water were used for the test, in order to determine a dependency of the water solubility on the amount of the test item added. Eight individual flasks (numbered 1A - 1C and 2 – 6) were prepared. Six vessels (flasks 1C (for the sampling point 72 h) and 2 – 6) and a blank were set onto the shaking apparatus immediately. After 24 ± 2 hours, flask 1B (for the sampling point 48 h) and after further 24 ± 2 hours, flask 1A (for the sampling point 24 h) were set on the shaker and all flasks were shaken for further 24 ± 2 hours at room temperature (20.0 ± 0.5 °C). Then, flasks 1A - 1C were taken from the shaker and stored at 20.0 ± 0.5 °C for equilibration. Samples were taken, membrane filtrated and analysed via HPLC. No differences above 15 % and no rising tendency in the concentration of the solutions were determined between sampling dates 1 day (flask 1A), 2 days (flask 1B) and 3 days (flask 1C), indicating that the maximum concentration of the test item had been reached on day 1. Therefore on day 3, flasks 2 –6 were sampled and analysed in the same fashion.

Samples were filtrated using Nylon filters 0.45 µm in method validation and in the pre-test for temperature dependency. In the main test, Nylon filters 0.2 µm were used, because after filtration with 0.45 µm filters, samples had been still turbid: a Tyndall effect (i.e. a laser beam was scattered when transmitted through the liquid). No Tyndall effect could be observed in the filtrates indicating that no colloidal dispersed particles were present after filtration through 0.2 µm.

Dependency of solubility on amount of the test item (nominal load) was not perceived. As equilibration was assumed to be complete on day 1, all measured concentrations of flasks 1A – 1C and 2 – 6 were used for calculation of the water solubility.

At the plateau, the concentration of PPDA in water had reached 5.60 ± 0.07 g/L at 20.0±0.5 °C.