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Partition coefficient

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Reference
Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1988-08-16 to 1988-08-18
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 107 (Partition Coefficient (n-octanol / water), Shake Flask Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
photometric method
Key result
Type:
log Pow
Partition coefficient:
-0.92
Temp.:
20 °C
pH:
7.4
Type:
Pow
Partition coefficient:
0.12
Temp.:
20 °C
pH:
7.4
Details on results:
- Preliminary test: a partition coefficient of 6.0E-02 was calculated (the absorption at 235 nm and 242 nm for the diluted n-octanol and water samples, respectively, was used)
- Significant differences were measured comparing the absorbance of a freshly prepared solution of the test substance in buffer (concentration: 5.2 µg/ml) and n-octanol (concentration: 4.6 µg/ml) and the same solutions after 4.5 hours (12 % and 13 % decrease, respectively).
- No conclusion can be made regarding the stability of the test substance in buffer and n-octanol.

Table 3: Individual measurements of the partition coefficient (n-octanol/water). Temperature of measurement 20+/-1°C.

Volume [ml]

Concentration after equilibrium

Total amount after equilibrium

Calculated partition coefficient

Mean partition coefficient

Octanol stock solution*

Octanol

Buffer

Octanol

[µg/ml]

Buffer

[µg/ml]

n-Octanol

[µg]

Buffer

[µg]

2

2

8

13.7

120.9

55

967

0.113

0.113

2

2

8

12.5

111.5

50

892

0.112

 

2

4

6

18.4

146.6

110

880

0.126

0.125

2

4

6

18

145.8

108

875

0.123

 

2

6

4

22.2

189.3

178

757

0.117

0.124

2

6

4

24.9

192.2

199

769

0.130

 

Mean value:

0.12

 

Relative standard deviation:

6%

 

* concentration of the test substance in n-octanol stock solution: 802.6 µg/ml (after UV analysis)

Conclusions:
The partition coefficient (n-octanol/water) of thiourea was determined to be 0.12 (log Pow: -0.92) at 20 +/-1°C.
Executive summary:

The partition coefficient (n-octanol/water) for thiourea was determined according to the OECD guideline for testing of chemicals number 107 (May 1981) and the EC method A.8, EEC Directive 84/449, Part L251 (September 1984) with the shake flask method. The measurements were conducted at 20°C +/- 1°C and resulted in a partition coefficient of 0.12 (log Pow: -0.92).

The study was performed in compliance with good laboratory practice (GLP).

Description of key information

There are three literature sources available. All results indicate that the partition coefficient is low.

In the key study the partition coefficient (n-octanol/water) of thiourea was determined to be 0.12 (log Pow: -0.92) at 20 ± 1 °C.

Key value for chemical safety assessment

Log Kow (Log Pow):
-0.92
at the temperature of:
20 °C

Additional information

Three literature sources are available reporting the partition coefficient of thiourea.

In a guideline study the partition-coefficient was determined according OECD guideline 107 with the shake flask method. The measurements were conducted at 20°C ± 1 °C and resulted in a partition coefficient of 0.12 (log Pow: –0.92) (Cardinaals, J.M., 1988).

According to the HSDB (hazardous substances databank), citing Govers et al. (1986) the partition coefficient of thiourea is –1.08 (log Kow).

According to the study report of Kotzias in "Überprüfung der Durchführbarkeit von Prüfungsvorschriften und der Aussagekraft der Grundprüfung des E. Chem. G. - Verteilungskoeffizient" the partition coefficient log Pow of thiourea is -1.61 (Korte and Greim, 1981).

The most reliable result, the determination of the partition coefficient according to OECD 107 was chosen as key value. Therefore the partition coefficient of thiourea is: logPow = –0.92 at 20°C ± 1 °C.

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