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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:
22 April 2010 and 02 June 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
in compliance with UK GLP standards (Schedule 1, Good Laboratory Practice Regulations 1999 (SI 1999/3106 as amended by SI 2004/0994))
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
gas chromatography
Key result
Type:
Pow
Partition coefficient:
163
Temp.:
23 °C
pH:
3.2
Key result
Type:
log Pow
Partition coefficient:
2.21
Temp.:
23 °C
pH:
3.2
Details on results:
- Preliminary estimate:
Partition coefficient: 234
Log10 Pow: 2.37

- Definitive test:
Samples 1 to 6 only used in overall mean calculations (Organic:Aqueous Volume Ratios 1:4, 1:2 and 1:1 respectively, all performed in duplicate)
Mean Pow : 163
log10 Pow : 2.21
Pow standard deviation : 61.4

Table 3: mean peak areas obtained for the standard, stock and sample solutions– Organic Phase

Solution

Mean Peak Area

Standard 322 mg/L

1.447 x 105

Standard 305 mg/L

1.126 x 105

Organic phase matrix blank

0

Sample 1

7.861 x 104

Sample 2

1.445 x 105

Sample 3

1.104 x 105

Sample 4

1.207 x 105

Sample 5

1.024 x 105

Sample 6

1.546 x 105

Standard 322 mg/L

1.428 x 105

Standard 305 mg/L

1.318 x 105

Stock solution A

1.609 x 105

Stock solution B

1.464 x 105

Standard 298 mg/L

1.219 x 105

Standard 304 mg/L

1.464 x 105

Organic phase matrix blank

0

Sample 7

1.056 x 105

Sample 8

1.277 x 105

Stock solution A

1.416 x 105

Stock solution B

1.344 x 105

Table 4: mean peak areas obtained for the standard, stock and sample solutions–Aqueous Phase

Solution

Mean Peak Area

Standard 145 mg/L

2.845 x 105

Standard 152 mg/L

3.368 x 105

Aqueous phase matrix blank

0

Sample 1

3.270 x 105

Sample 2

2.768 x 105

Sample 3

3.024 x 105

Sample 4

1.750 x 105

Sample 5

2.650 x 105

Sample 6

2.288 x 105

Standard 156 mg/L

2.885 x 105

Standard 155 mg/L

2.843 x 105

Aqueous phase matrix blank

0

Sample 7

3.266 x 105

Sample 8

3.448 x 105

Table 5: total weights (mg) and analysed concentration (mg/l)

Sample Number

Total Weight (mg)*

Organic Phase

Aqueous Phase

Analysed Concentration (mg/L)

Weight (mg)†

Analysed Concentration (mg/L)

Weight (mg)†

pH

1

263

1.92 x 103

144

23.5

7.05

3.2

2

263

3.53 x 103

265

19.9

5.97

3.2

3

351

2.97 x 103

270

21.7

4.35

3.2

4

351

2.95 x 103

295

12.6

2.52

3.2

5

561

2.50 x 103

400

19.1

3.05

3.1

6

561

3.78 x 103

604

16.4

2.63

3.1

7

233

2.37 x 103

178

26.6

7.99

3.2

8

233

2.87 x 103

215

28.1

8.44

3.2

* From analysis of the stock solution

From analysis of the respective phase

pH of n-octanol saturated water:       5.2
Temperature:
                          23.0 ± 0.5 °C

(Data from repeated test not used since the temperature of the test was outside limits specified in the guidelines)

Table 6: The partition coefficient determined for each sample

Sample Number

Organic:Aqueous Volume Ratio

Partition Coefficient

Log10Pow

Mean Partition Coefficient

1

1:4

81.6

1.91

129

2

177

2.25

3

1:2

124

2.09

179

4

234

2.37

5

1:1

131

2.12

180

6

230

2.36

7

1:4

89.1

1.95

95.6

8

102

2.00

Conclusions:
The partition coefficient of the test material has been determined to be 163, log10 Pow 2.21 at 23.0 ± 0.5 °C.
Executive summary:

The partition coefficient of the test material was determined in a GLP compliant study performed to EU Method A.8. The partition coefficient of the test material was determined to be 163, log10 Pow 2.21 at 23.0 ± 0.5 °C.

Description of key information

The partition coefficient of test material was determined in a GLP compliant study performed to EU Method A.8. The partition coefficient of the the test material was determined to be 163, log10 Pow 2.21 at 23.0 ± 0.5 °C.

Key value for chemical safety assessment

Log Kow (Log Pow):
2.21
at the temperature of:
23 °C

Additional information

Butler RE and White DF (2010) was selected as the key study for the partition coefficient of the test material as the study was performed to a current accepted guideline, in compliance with GLP. As such, the study was deemed to be of a high reliability, and adequate as a stand-alone data source. A reliability rating of 1 was assigned to this study, according to the criteria of Klimisch, 1997.

In the ASTDR (2005) report a partition coefficient of approximately 2,180 at 20 °C was calculated by Maguire et al. (1985) to estimate the adsorption of tributyltin ions by lake sediments. A reliability rating of 4 was assigned to this study, according to the criteria of Klimisch, 1997 as this information is from a secondary source.

In the ATSDR (2005) report, the Kow of the test material at pH 6 was reported to be approximately 1,585 by Maguire et al. (1983).

A reliability rating of 4 was assigned to this study, according to the criteria of Klimisch, 1997 as this information is from a secondary source.

In the Canadian Environmental Protection Act (1993) report, the logarithms of the n-octanol-water partition coefficients (log Kow) for the test material is 2.2, (Tsuda et al., 1988). A reliability rating of 4 was assigned to this study, according to the criteria of Klimisch, 1997 as this information is from a secondary source and no methodology was reported.

In the Tsuda et al (1990) study, the Pow of the test material was reported to be between 1608 - 12,195 at at temperature of 25 °C and a a pH of between 5.8 - 8. The study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of the relevant results therefore a reliability rating of 2 was assigned to this study, according to the criteria of Klimisch, 1997.

In the Tsuda et al (1986) study, the Log Pow was calculated to be approximately 2.07 ± 0.014.

A reliability rating of 3 was assigned to this study, according to the criteria of Klimisch, 1997 due to the following restrctions:

The method of analysis involved derivatisation. This method only measures the amount of the alkyltin moiety, DBT, present and does not identify the other ligands attached to the tin. The low solubility and hydrolysis chemistry of these compounds present significant challenges to measuring the organotins in aqueous solution. None of the current analytical methods (e.g., alkyl or hydride derivatization) are acceptable for quantifying the resulting products of hydrolysis, as the parent compound, soluble impurities, and hydrolysis products will be derivatized to the same final tetraalkyltin or alkyltin hydride compound and there can be no differentiation between starting material and hydrolysis products. Therefore, the reported value may be influenced by the presence of more water-soluble impurities or hydrolysis products. The influence of impurities is not sufficiently documented.