4-hydroxybenzaldehyde

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15. - 20.01.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient - Shake Flask Method)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

no

Type of method:

flask method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

log Pow

Partition coefficient:

1.3

Temp.:

23 °C

pH:

>= 6 - <= 6.7

Preliminary visual estimation of the n-octanol solubility

Defined amounts of the test item were stirred with increasing volumes of n-octanol at room temperature and visually checked for any undissolved parts.

Table 1: Results of the preliminary visual estimation of the n-octanol solubility

Amount of test item / mg	Added volume of n-octanol / mL	Total volume of n-octanol / mL	Stirring time / h	Appearance of mixture
12.1	10	10	1	dissolved
103.4	10	10	0.5	dissolved
197.6	10	10	0.5	dissolved
497.2	5	5	0.5	dissolved
1014.1	5	5	22	not dissolved

According to this preliminary test the solubility of the test item in n-octanol was between 99 g/L and 203 g/L (without correction for the purity).

 

Calculation of the partition coefficient log P_ow from the preliminary test

The partition coefficient P_ow may be estimated from the saturation concentrations in n-octanol and water by the following equation:

P_ow = c_S^n-octanol / c_S^water

c_S = saturation concentration in g/L

The estimated partition coefficient was calculated with the water solubility data (cs = 7.77 g/L (± 0.03 g/L)) and the data obtained for the preliminary solubility in n-octanol. It was calculated to be in the range of: 1.1 < log Pow < 1.4.

Also the program KOWWIN (part of EPI Suite) was used for calculating the log Pow of the test item. The calculated value was: 1.2. Therefore, according to the guidelines the partition coefficient n-octanol/water of the test item at room temperature was determined by the shake flask method.

 

Shake flask method

A specified amount of the test item was dissolved in 100 mL n-octanol (saturated with demin. water). 10 mL of this solution were added to six different flasks (experiment: 1A, 1B. 2A. 2B, 3A, 3B). Subsequently, different amounts of n-octanol (saturated with demin. water) and 20 mL demin. water (saturated with n-octanol) were added to the flasks. All mixtures were shaken for several minutes at ambient temperature (23 °C). After separation of the phases each phase was centrifuged (30 minutes at 23 °C and 15000 rpm) and the pH values of the aqueous phases were measured. For analytics the samples were prepared and subsequently the concentrations of the test item in the different phases were determined by HPLC.

 

Table 2: Test conditions and results of the shake flask method

Experiment	1A	1B	2A	2B	3A	3B
Amount of test item / mg	94.1
Concentration of the stock solution / mg/L	941
Volume of added stock solution / mL	10	10	10	10	10	10
Volume of added n-octanol / mL	0	0	10	10	30	30
Volume of added demin. Water / mL	20	20	20	20	20	20
pH of the aqueous phase at 23 °C	6.7	6.4	6.7	6.4	6.1	6.0
Measured concentration in aqueous phase / mg/L	0.85/0.85	0.90/0.90	0.52/0.52	0.45/0.45	0.23/0.23	0.23/0.23
Mean concentration in aqueous phase / mg/L*	42.5	45.2	26.0	22.5	11.4	11.4
Measured concentration in n-octanol phase / mg/L	6.81/6.81	8.30/8.30	4.22/4.22	4.35/4.37	2.18/2.18	2.26/2.26
Mean concentration in* n-octanol phase / mg/L	681.1	829.9	422.0	436.2	218.1	226.2

* For the mean concentration the sample preparation (dilution) is taken into account.

The following partition coefficients are calculated from the measured and unrounded concentration values and not from the rounded values given in the table above.

 

Table 3: Partition coefficients of the shake flask method

Experiment	Pow	log Pow	Average log Pow
1A	16.01	1 20	1.23
1B	18.35	1.26
2A	16.23	1.21	1 25
2B	19.43	1.29
3A	19 17	1.28	1.29
3B	19.60	1.29
Mean value (experiment 1A to 3B)			1.26
Standard deviation			0.04

The six determined log P_ow values are within a range of ± 0.3 units as requested by the guideline. The partition coefficient P_ow of the test item was determined to be: log P_ow = 1.3

Conclusions:

The partition coefficient of the test item was determined to be 1.3 at 23 °C and pH 6.0 - 6.7.

Executive summary:

A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. A stock solution of the test substance was prepared in n-octanol pre-saturated with water. Test vessels with octanol/water mixture in different ratios were shaken for several minutes. After separation of the phases each phase was centrifuged (30 minutes at 23 °C and 15000 rpm) and the pH values of the aqueous phases were measured. For analytics the samples were prepared and subsequently the concentrations of the test item in the different phases were determined by HPLC. The partition coefficient of the test item was determined to be 1.3 at 23 °C and pH 6.0 - 6.7.

Description of key information

The partition coefficient of the test item was determined to be 1.3 at 23 °C and pH 6.0 - 6.7 (reference 4.7-1).

Key value for chemical safety assessment

Log Kow (Log Pow):

1.3

at the temperature of:

23 °C

Additional information

A study was conducted in accordance with OECD TG 107 and Regulation (EC) No 440/2008 method A.8 to determine the partition coefficient of the test substance using the shake flask method. A stock solution of the test substance was prepared in n-octanol pre-saturated with water. Test vessels with octanol/water mixture in different ratios were shaken for several minutes. After separation of the phases each phase was centrifuged (30 minutes at 23 °C and 15000 rpm) and the pH values of the aqueous phases were measured. For analytics the samples were prepared and subsequently the concentrations of the test item in the different phases were determined by HPLC. The partition coefficient of the test item was determined to be 1.3 at 23 °C and pH 6.0 - 6.7 (reference 4.7-1).