Methyl (R)-2-(4-hydroxyphenoxy)propionate

Partition coefficient

Description of key information

Campbell et al. (1993): Under the conditions of this study, the log Pow was determined to be 1.29 at 22 °C when tested at pH 4, 7 and 9.

Caesar (1991): Under the conditions of this study, the partition coefficient of the test material at 25 °C was determined to be 25.2 and the log Pow was determined to be 1.40.

Key value for chemical safety assessment

Log Kow (Log Pow):

1.29

at the temperature of:

22 °C

Additional information

Two studies are available to address this endpoint and both are considered to be key as the data are equally reliable. The studies were assigned a reliability score of 1 in accordance with the criteria for assessing data quality set forth by Klimisch et al. (1997).

Campbell et al. (1993)

The partition coefficient of the test material was investigated in a study which was performed in accordance with the standardised guidelines OECD 107 and EU method A.8 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Investigation of the octanol:buffer partition coefficient was carried out at 22 ± 0.5 °C using the flask method. Aliquots from each layer were analysed along with standard and quality control samples. The test was performed using buffered aqueous phases at pH 4, 7 and 9. An approximately 1 mg/mL solution of test material in pre-saturated octanol was accurately prepared for each of the aqueous phases under investigation.

Screw capped tubes were prepared containing 3, 5 and 6 mL of stock solution with 6, 5 and 3 mL of the relevant aqueous phase, respectively. Samples were prepared in duplicate. The tubes were then manually inverted 100 times prior to centrifugation at 3000 rpm for 15 min to separate the layers. Aliquots were then taken from each phase for analysis.

The mean values for the partition coefficient at pH 4.0, 7.0 and 9.0 were 19.40, 19.44 and 19.48, respectively. Log Pow values were 1.29, 1.29 and 1.29, respectively.

Under the conditions of this study, the log Pow was determined to be 1.29 at 22 °C when tested at pH 4, 7 and 9.

Caesar (1991)

The partition coefficient of the test material was investigated in accordance with the standardised guideline EU Method A.8 under GLP conditions using the flask method.

Known amounts of the test material were weighed into 25.0 mL of 1-octanol, 25 mL of water was added and the mixture was allowed to come to equilibrium. After the phases had separated the aqueous phase was removed, centrifuged at about 3000 rpm for about 30 minutes, and the lower aqueous phase was removed.

The latter was extracted with chloroform and the concentration of the test material in the chloroform extract was determined through gas chromatography using an external standard.

The values obtained were recalculated for the aqueous phase from which the extractions had been carried out. All measurements were done at ambient temperature (25 °C).

Under the conditions of this study, the partition coefficient of the test material at 25 °C was determined to be 25.2 and the log Pow was determined to be 1.40.