Butylamine

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Study initiation date: 24 June 2009 Study completion date: 12 October 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Version / remarks:

Adopted: 13 April 2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient)

GLP compliance:

yes

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Key result

Type:

Pow

Partition coefficient:

1

Temp.:

25 °C

pH:

7.5

Key result

Type:

log Pow

Partition coefficient:

0

Temp.:

25 °C

pH:

7.5

Summary of the results of the HPLC measurements of the reference compounds and the test item:

Sample no.^1)	tR1 [min]	tR2 [min]	tR [min]	k‘	log k'(x)	log Pow (y)
0	0.80	0.80	0.80
1	1.54	1.54	1.54	0.925	-0.034	0.3^2)
2	1.64	1.64	1.64	1.050	0.021	0.5^2)
3	2.13	2.13	2.13	1.663	0.221	0.9^2)
4	4.95	4.96	4.96	5.200	0.716	1.7^2)
5	7.38	7.38	7.38	8.225	0.915	1.9^2)
6	10.53	10.53	10.53	12.163	1.085	2.1^2)
7	47.84	47.89	47.87	58.838	1.770	3.4^2)
Test item	1.24			0.550	-0.260	0.014^3)
Test item		1.24		0.550	-0.260	0.014^3)
Mean value						0

1) For the names of the reference compounds see corresponding table in materials and methods section.

2) Results from the OECD guideline for the testing of chemicals No. 117: "Partition Coefficient (n-octanol/water), HPLC method" (13 April 2004).

3) Interpolated from linearized function log Pow = f(log k' ) of the calibration data.

The log Pow-values of the test item fall within a range of ± 0.1 units, thus the test is satisfactory

The following linear regression equation was obtained from the calibration substances:

y = 1.6424 * x + 0.44148,

y being log Pow, and x being log k'.

The linear regression of log k' of the calibration substances against their log Pow has a correlation coefficient of r = 0.9969.

Conclusions:

Partition coefficient n-octanol / water (Pow; OECD 117): Pow = 1 / log Pow = 0 (pH 7.5; 25 °C)

Executive summary:

The partition coefficient n-octanol / water (Pow) of the test item was determined compliant with GLP according to OECD guideline no. 117 [adopted on 13 April 2004] and EU test method A.8 [Directive 92/69/EEC, Official Journal L 383 A 1992] with the HPLC method.

Result:

Partition coefficient n-octanol / water (Pow; OECD 117): Pow = 1 / log Pow = 0 (pH 7.5; 25 °C)

Description of key information

Partition coefficient n-octanol / water (Pow; OECD 117): Pow = 1 / log Pow = 0 (pH 7.5; 25 °C)

Key value for chemical safety assessment

Log Kow (Log Pow):

0

at the temperature of:

25 °C

Additional information

In the key study (AQURA, 2009) the partition coefficient n-octanol / water (Pow) of the test item was determined compliant with GLP according to OECD guideline no. 117 [adopted on 13 April 2004] and EU test method A.8 [Directive 92/69/EEC, Official Journal L 383 A 1992] with the HPLC method.

Result:

Partition coefficient n-octanol / water (Pow; OECD 117): Pow = 1 / log Pow = 0 (pH 7.5; 25 °C).

Due to an experimentally determined pKa of 10.8 for n-butylamine, at pH 7.5 approximately 99.95 % will be dissociated based on the Henderson-Hasselbach equation. As such, the determined Pow may be taken as Dow and is environmentally relevant.

Pow for the non-dissociated state has not been determined in this study.

 

However, supporting data (BASF, 1987) are available for a non-buffered system:

Two replicate experiments were performed at 23 °C using different concentrations of n-butylamine (second conc. ca. factor of 2 higher than first conc.). The Pow was determined from measurement of n-butylamine concentration in the octanol phase and water phase:

Pow (conc. 1): 6.52

Pow (conc. 2): 6.55

Pow (arithmetic mean): 6.54, log Pow 0.815 (23 °C)

pH was not buffered / adjusted and must have been alkaline based on the pKa of 10.8 for n-butylamine. However, pH values for aqueous phase was not reported.

 

Discussion:

Based on BASF (1987), the measured concentrations in water were (1) 0.0192 mol/L and (2) 0.0397 mol/L. Based on a mean concentration of 0.02945 mol/L a pH value in the aqueous phase of approximately 11.6 can be calculated. This corresponds to a neutral fraction of 86 % according to the Henderson-Hasselbach equation.

In consequence, the Pow of 6.54 may be taken as an approximate for the neutral state of n-butylamine at highly alkaline pH, while the value of Pow =1 determined in the key study corresponds to the octanol-water partition coefficient at environmentally relevant pH values (pH 7.5).