4-acetyl-2-methylbenzoic acid

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2019

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

4-acetyl-2-methylbenzoic acid

EC Number:

856-079-4

Cas Number:

55860-35-0

Molecular formula:

C10H10O3

IUPAC Name:

4-acetyl-2-methylbenzoic acid

Test material form:

solid: particulate/powder

Study design

Analytical method:

high-performance liquid chromatography

Results and discussion

Partition coefficient

Partition coefficient 1

Key result

Type:

log Pow

Partition coefficient:

0.14

Temp.:

20 °C

pH:

5

Partition coefficient 2

Key result

Type:

log Pow

Partition coefficient:

-1.6

Temp.:

20 °C

pH:

6.8

Partition coefficient 3

Key result

Type:

log Pow

Partition coefficient:

-2.5

Temp.:

20 °C

pH:

8.9

Details on results:

Experiment at pH 5.0: The equilibration concentrations of the test item in either of the two, clear, separated phases were all less than 1.782 g/L, i.e. less than 0.01 molar. In the experiment using the citrate buffer solution, the individual log Pow values of the six samples varied between 0.12 and 0.15, clearly falling within the requirement of ±0.3 log units.
Experiments at pH 7.0 and 9.0: In the experiment using the phosphate buffer solution, the individual log Pow values of the six samples varied between -1.56 and -1.57, clearly falling within the requirement of ±0.3 log units. In the experiment using the borax buffer solution, the individual log Pow values of the six samples varied between -2.52 and -2.54, clearly falling within the requirement of ±0.3 log units.

Applicant's summary and conclusion

Conclusions:

The octanol-water partition of the acidic test substance was found to be dependent on the pH value. The average values determined with the shake flask method were log Kow = 0.14 at pH 5.0, log Kow = -1.6 at pH 6.8 and log Kow = -2.5 at pH 8.9

Executive summary:

The octanol-water partition coefficient of the substance was studied under GLP to OECD TG 107 (1995), using the shake flask method. Octanol of high purity ≥99.5% was used in the experiments. As the test substance is an acidic compound, the octanol / water partition coefficient is pH dependent, and was determined at three different pH values by using appropriate buffer solutions. Prior to use, both the 1-octanol and the respective buffer solutions had been mutually saturated with each other and then allowed to stand for sufficient time to allow phase separation. Three octanol / buffer solution volume ratios were investigated: the second having twice the ratio of the first and the third half the ratio of the first. Each of the three volume ratios was prepared in duplicate. At each tested pH value, an accurate volume of octanol was first filled into centrifuge tubes. The pH of the respective buffer solution was determined, and after the addition of the appropriate volume of buffer solution, the centrifuge tubes were sealed and rotated through 180 degrees about their transverse axis hundred times. The contents of the tubes were then equilibrated by continuous, gentle shaking for about twenty-four hours at 20.0 °C (± 0.5 °C) in a thermostatically controlled water bath. The tubes were then centrifuged for forty minutes at 48000 G in a centrifuge thermostated at 20 °C. Subsequently, an aliquot from each of the clear, separated, octanol and aqueous phases was removed by pipette from each centrifuge tube and analysed by a suitable analytical method (HPLC with external standard), for which accuracy (with regards to linearity, recovery, specificity and precision) was demonstrated. Additionally, the pH of each of the aqueous phases was also determined.