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Partition coefficient

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Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2014-02-24 to 2014-03-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
shake-flask method to: flask method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
5
Temp.:
25 °C
Remarks on result:
other: pH value not stated in the report
Details on results:
The concentration of test substance in the 1-octanol and water phase was analysed after 24 hours. The Log Pow values of the replicates were calculated using the final concentrations. The average Log Pow value for tert-butyl peroxyneodecanoate was calculated to be 5.0. The observed partition coefficient showed that the test substance dissolved well in 1-octanol and only poorly in water.

Results of definitive test

Replicate

Octanol phase

Water phase

Pow

log Pow

meas.

conc.

mg/L

dilution factor

final conc.

µg/L

meas.

conc.

mg/L

dilution factor

final conc.

µg/L

1

172.6

15

2588496

25.5

1

25.5

1.0.E+05

5.0

2

174.9

15

2624142

25.9

1

25.9

1.0.E+05

5.0

3

172.0

15

2579322

26.8

1

26.8

9.6.E+04

5.0

Calibration curves

Date

Matrix

Calibration curve

R2

Accuracy

17-03-2014

water

y = -1.34E-06x2 + 0.010x + 0.034

0.9999

96.2 – 102.8 %

octanol

y = -7.97E-06x2 + 0.034x – 0.026

0.9985

90.9 – 110.3 %

18-03-2014

water

y = 1.27E-07x2 + 0.009x + 0.070

0.9999

95.0 – 109.8 %

octanol

y = -1.23E-05x2 + 0.032x – 0.003

0.9992

94.5 – 107.4 %

19-03-2014

water

y = 1.88E-06x2 + 0.008x + 0.096

0.9998

95.6 – 104.7 %

octanol

y = 4.60E-06x2 + 0.027x + 0.283

0.9997

90.7 – 112.4 %

20-03-2014

water

y = -2.16E-06x2 + 0.011x + 0.055

0.9997

95.1 – 104.9 %

octanol

y = 1.35E-06x2 + 0.033x – 0.003

0.9985

91.0 – 110.5 %

25-03-2014

water

y = -2.39E-07x2 + 0.010x + 0.068

0.9999

92.7 – 101.7 %

octanol

y = -1.05E-05x2 + 0.036x – 0.089

0.9991

92.8 – 114.7 %

Conclusions:
Using the slow stirring method the log Pow was determined to be 5.00 at 25 °C.
Executive summary:

A study was conducted according to OECD TG 123 slow stirring method to determine the partition coefficient of the test substance. In a preliminary test the length of the equilibration period was assessed. Therefore one reaction vessel was prepared according to the test procedure. At time points 6, 24, 48 and 72 hours after adding the test substance, the concentration of the test substance was determined in both the 1-octanol and water phase. The Log Pow calculated using the final concentrations of the test substance at four consecutive time points, showed no significant difference over the several time points. Thus, for practical reasons, an equilibration period of 24 hours was chosen to be used during the definitive test. In the main test 3 reaction vessels were prepared following the test protocol. The test was performed in the dark and at a temperature of 25 ± 1°C. At 24 hours after adding the test substance, stirring was stopped and samples were taken from the octanol as well as the water phase. The samples were analysed using HPLC method with UV detection. Two different method were used for the determination of octanol and water samples. For the determination of the aqueous samples a Solid Phase extraction was conducted. The octanol samples were directly measured. The concentrations of the test substance in the samples were calculated from the relation between concentration of standards and peak area obtained with quadratic regression analysis. The average Log Pow value for tert-butyl peroxyneodecanoate was calculated to be 5.0. All validation criteria were fulfilled. No observations were made which have cause doubts concerning the validity of the study outcome.

Endpoint:
partition coefficient
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2002-05-14 to 2002-05-16
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study; OECD guideline was followed
Qualifier:
according to
Guideline:
OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)
Version / remarks:
adopted March 30, 1989
Deviations:
no
Qualifier:
according to
Guideline:
EU Method A.8 (Partition Coefficient)
Version / remarks:
December 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC method
Partition coefficient type:
octanol-water
Analytical method:
high-performance liquid chromatography
Key result
Type:
log Pow
Partition coefficient:
>= 5.1 - <= 5.4
Temp.:
20 °C
pH:
5.9
Details on results:
Six common standards, which have known log Pow values in the range of 1.1 to 6.2, were used as reference standards during the main test. The test item solution was injected three times and combined reference item solution was injected six times. The thiourea solution was injected two times. The log Pow was calculated using a regression curve. The test item produces 5 peaks during the HPLC run which correspond to the log Pow beetween 5.1 and 5.4. The chromatography of the test item shwoed five peaks with well-defined and reproducible retention times. The five peaks arise from the different geometric isomers present in the test item. The resultant log Pow was in the range of the estimated value found during the preliminary test. Based on the chromatographic data, the test item was considered to be stable during the test procedure.
Conclusions:
The n-octanol/water partition coefficient of tert-butyl peroxyneodecanoate was determined to be between log Pow = 5.1 to log Pow = 5.4 using the HPLC method.
Executive summary:

The partition coefficient (n-octanol/water) of tert-butyl peroxyneodecanoate was determined using the HPLC method according to EU method A.8 and OECD guideline no. 117. The n-octanol/water partition coefficient of tert-butyl peroxyneodecanoate was determined to be between log Pow = 5.1 to log Pow = 5.4.

Description of key information

The n-octanol/water partition coefficient of tert-butylperoxyneodecanoate was determined to be between logPow= 5.0 using the slow stirring method.

Key value for chemical safety assessment

Log Kow (Log Pow):
5
at the temperature of:
25 °C

Additional information

Summary

Two studies were conducted to determine the partition coefficient octanol water of the test substance.

In a first approach using the HPLC method according to OECD TG 117 the log Pow was determined to be in range from 5.1 to 5.4 at 20 °C. This method was used for screening purpose. According to the guidance on information requirements and chemical safety assessment (IR/CSA) Chapter R.7a Version 2.3 as of December 2013 the slow-stirring method is recommended for substances with an estimated log Pow >5. Thus, a second study according to OECD TG 123 was conducted to refine and verify the former determined logPow. The log Pow was determined as average of three independent experiments. This study was conducted at a temperature of 25 °C which is the recommended value of the IR/CSA guidance. In contrary as the OECD TG 117 gives no further specification this study was conducted at 20 °C. As the log Pow is temperature-dependent the determination at 25 °C was regarded to be most reliable as it is in line with the guidance requirements. Furthermore the calculation of the logPow according to OECD 123 is based on the directly measured concentration of the test substance in each phase. In contrast the HPLC method is based on an indirect determination of the log Pow using the retention time. Taken all aspects into account the log Pow of 5.00 was regarded as most reliable and was therefore chosen as key parameter for risk assessment.

OECD 117 HPLC method (RCC ltd 2002)

The partition coefficient (n-octanol/water) of tert-butyl peroxyneodecanoate was determined using the HPLC method according to EU method A.8 and OECD guideline no. 117. The n-octanol/water partition coefficient of tert-butyl peroxyneodecanoate was determined to be between log Pow = 5.1 to log Pow = 5.4.

OECD TG 123 slow stirring method (Akzo Nobel N.V. 2014)

A study was conducted according to OECD TG 123 slow stirring method to determine the partition coefficient of the test substance. In a preliminary test the length of the equilibration period was assessed. Therefore one reaction vessel was prepared according to the test procedure. At time points 6, 24, 48 and 72 hours after adding the test substance, the concentration of the test substance was determined in both the 1-octanol and water phase. The Log Pow calculated using the final concentrations of the test substance at four consecutive time points, showed no significant difference over the several time points. Thus, for practical reasons, an equilibration period of 24 hours was chosen to be used during the definitive test. In the main test 3 reaction vessels were prepared following the test protocol. The test was performed in the dark and at a temperature of 25 ± 1°C. At 24 hours after adding the test substance, stirring was stopped and samples were taken from the octanol as well as the water phase. The samples were analysed using HPLC method with UV detection. Two different method were used for the determination of octanol and water samples. For the determination of the aqueous samples a Solid Phase extraction was conducted. The octanol samples were directly measured. The concentrations of the test substance in the samples were calculated from the relation between concentration of standards and peak area obtained with quadratic regression analysis. The average Log Pow value for tert-butyl peroxyneodecanoate was calculated to be 5.0. All validation criteria were fulfilled. No observations were made which have cause doubts concerning the validity of the study outcome.