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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
05-May-2010 to 23-Sep-2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Media:
other: not applicable
Radiolabelling:
no
Test temperature:
Room temperature (21.1 °C)
Details on study design: HPLC method:
HPLC-Conditions
Apparatus: Merck-Hitachi autosampler L-7200
Merck-Hitachi pump L-6200
Merck-Hitachi L-7400
Column: LiChrospher 100 CN, particle size 5 µm, 250 x 4.6 mm
HPLC Eluent: Water / methanol (45:55; v/v); pH 6.3
Detection: Test item: 210 nm
Reference items: 210 nm
Sodium nitrate: 210 nm
Temperature: Room temperature (21.1 °C)
Injection Volume: 20 µL
Flow: 1.0 mL/min
Run Time: 15 minutes
Retention Times: See Table 1


Analytical monitoring:
not required
Type:
Koc
Value:
1 009.48 L/kg
Temp.:
21.1 °C
Remarks on result:
other: % Org Carbon not reported
Type:
log Koc
Value:
3 dimensionless
Temp.:
21.1 °C
Remarks on result:
other: % Org Carbon not reported
Details on results (HPLC method):
Due to the nature and tabular content of this information it would be rendered less comprehensible by splitting this information between sections. Therefore please see section “Any other information on materials and results incl tables”
Transformation products:
not measured

The test item solution was injected three times and the combined reference solution was injected six times. In the present study the reference items covered the range of log KOC1.25 to log KOC 5.63.

 

Three peaks were observed. The first two were not evaluated because their retention times correlate to known substances; the first one relates to tert-butanol and the second one relates to tert-butylhydroxyperoxide. The 3rdpeak obtained by HPLC was assigned todi-tert-butyl peroxide (CAS# 110-05-4) and therefore the KOCvalue of this peak is calculated as given inTable3.The assignment of the peaks was performed without GLP compliance.The test item was analyzed byNMRspectroscopy (study C95970) and found to be pure. Therefore, it can be concluded that the test item degraded on the column and not during storage.

 

The log KOCof the test item were calculated using a regression curve (log k' vs. log KOC) and was found to be 3.0, which is equal to a KOCvalue of 1009.48 (see Table 3). This value indicates that the mobility of di-tert-butyl peroxide (CAS# 110-05-4) is low.

 

The tabulated values represent rounded mean results, which were obtained by calculation using the exact raw data.

 

A typical HPLC chromatogram of the reference standard mixture is shown in the attached Figure 1. An HPLC chromatogram of the test item is shown in the attached Figure 2. A typical chromatogram of the determination of the dead-time is given in the attached Figure 3. The chromatography of the test item resulted inresulted in three peakswith well-defined and reproducible retention times. The HPLC method was therefore considered to be suitable for the purpose of the study.

 

The retention times of the individual measurements of the reference items, test item and the dead time are given in Table 1.The capacity factor (k’) was calculated for each reference item using the retention times. Log KOCwas plotted versus log k’ for each component to obtain a regression curve (Table 2 and Figure 4). The values given represent rounded values using the exact raw data.

 

Table 1       Retention Times in Minutes of the Reference Items and the Test Item

 

1strun

2ndrun

3rdrun

4thrun

5thrun

6thrun

Sodium nitrate

(= dead time)

1.625

1.558

1.625

1.575

-

-

Reference Items:

Acetanilide

3.425

3.742

3.425

3.425

3.417

3.417

Isoproturon

3.983

4.308

3.975

3.983

3.975

3.983

Linuron

4.600

4.933

4.592

4.608

4.592

4.608

Pyrazophos

5.733

6.092

5.725

5.767

5.717

5.758

Diclofop-methyl

6.375

6.742

6.358

6.417

6.358

6.408

2,4-DDT

9.108

9.525

9.092

9.642

9.083

9.175

di-tert-butyl peroxide (CAS# 110-05-4):

 

 

 

1stPeak*

(related to tert-Butanol)

2.717

2.717

2.717

 

 

 

2ndPeak*

(related to tert-Butyl-hydroxyperoxide)

3.600

3.600

3.600

 

 

 

3rdPeak

(related to di-tert-butyl-peroxide

(CAS#110-05-4))

5.000

5.000

4.967

 

 

 

* not evaluated

 

Table 2       Results of Linear Regression of Log k’ vs. Log KOC

 

Number
of
analysis

Mean retention time
[min]

k'

log k'

log KOC

Sodium nitrate (= dead time)

4

1.60

-

-

 

Reference Items:

Acetanilide

6

3.48

1.18

0.07

1.25

Isoproturon

6

4.03

1.53

0.18

1.86

Linuron

6

4.66

1.92

0.28

2.59

Pyrazophos

6

5.80

2.63

0.42

3.65

Diclofop-methyl

6

6.44

3.04

0.48

4.20

2,4-DDT

6

9.27

4.81

0.68

5.63

 

slope =

 

 

 

0.136

Linear Regression:

y-axis intercept =

-0.081

 

coefficient of regression (r) =

0.999

 

The tabulated values represent rounded results, which were obtained by calculation using the exact raw data.

 

The retention time of the first peak of the test item peak in all runs is shorter than the retention time of acetanilide, the first reference item on the list of the guideline with a log KOC value of 1.25.

 

Table 3       Result of di-tert-butyl peroxide (CAS# 110-05-4) Analyses

Number
of
analyses

Retention time
[min]

k'

log k'

log KOC

Mean
log KOC

KOC

Mean
KOC

Test Item Peak

1

5.00

2.13

0.3290566

3.0

3.0

1033.288

1009.4814

2

5.00

2.13

0.3290566

3.0

1033.288

3

4.97

2.11

0.3248261

3.0

961.8676

 

 

The tabulated values represent rounded results, which were obtained by calculation using the exact raw data.

 

 

Validity criteria fulfilled:
yes
Conclusions:
The log of the adsorption coefficient (KOC) of di-tert-butyl peroxide (CAS# 110-05-4) was calculated to be log KOC = 3.0 which is equal to a KOC value of 1009.48 using the HPLC method. Three peaks were identified in the chromatograms; they corresponded to tert-butanol, tert-butyl hydroperoxide and di-tert-butyl peroxide. The test material was analyzed for purity and composition by 1H and 13C NMR and found to be composed entirely of di-tert-butyl peroxide, proving that the parent compound was still intact but that it partially decomposed during the preparation of the test solutions and analysis.

The Koc of tert-butanol was calculated to be <18 (log Koc <1.25); the Koc of tert-butyl hydroperoxide was determined to be 21 (log Koc 1.3). The Koc of di-tert-butyl peroxide was calculated to be 1009; the log Koc of di-tert-butyl peroxide was calculated to be 3.0. This value indicates the di-tert-butyl peroxide is not expected to be highly mobile in the environment, but the appearance of breakdown products suggests that the molecule may decompose under certain conditions to more mobile products.

Executive summary:

The adsorption coefficient is defined as the ratio between the concentration of the substance in the soil/sludge and the concentration of the substance in the aqueous phase at adsorption equilibrium. The adsorption coefficient normalized to the organic carbon content of the soil KOCis a useful indicator of the binding capacity of a chemical on organic matter of soil and sewage sludge and allows comparisons to be made between different chemicals.

 

The experimental method uses HPLC for the estimation of the adsorption coefficient KOCin soil and sewage sludge.

The determination of the adsorption coefficient (KOC) of di-tert-butyl peroxide (CAS# 110-05-4) was performed according to the OECD Guideline for the Testing of Chemicals, No. 121, Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge using High Performance Liquid Chromatography (HPLC), January, 2001, the EC Directive 2001/59, C.19 (August 2001) and Council Regulation (EC) No. 440/2008, 30 May 2008, Part C, Methods for the determination of physico-chemical properties, C.19.

The log of the adsorption coefficient (KOC) of di-tert-butyl peroxide (CAS# 110-05-4) was estimated to be in the range:

 

Three peaks were identified in the chromatograms; they corresponded to tert-butanol, tert-butyl hydroperoxide and di-tert-butyl peroxide. The test material was analyzed for purity and composition by 1H and 13CNMRand found to be composed entirely of di-tert-butyl peroxide, proving that the parent compound was still intact but that it partially decomposed during the preparation of the test solutions and analysis.

 

The Koc of tert-butanol was calculated to be <18 (log Koc <1.25); the Koc of tert-butyl hydroperoxide was determined to be 21 (log Koc 1.3). The Koc of di-tert-butyl peroxide was calculated to be 1009; the log Koc of di-tert-butyl peroxide was calculated to be 3.0. This value indicates the di-tert-butyl peroxide is not expected to be highly mobile in the environment, but the appearance of breakdown products suggests that the molecule may decompose under certain conditions to more mobile products.

Description of key information

The Koc of the substance was calculated as 1009.48 using OECD 121.
The Log Koc of the test substance was therefore approximately 3.

Key value for chemical safety assessment

Koc at 20 °C:
1 009

Additional information

The adsorption coefficient of the substance in soil and sludge using an HPLC method was estimated in a reliable GLP study following OECD 121. On chromatograms, three peaks were observed when injecting the substance. The two first peaks were identified to be tert-butanol and ter-butyl hydroxyperoxide which were thought to be impurities or degradation products of the ter-butyl peroxide. Based on three measurements of the substance, and by comparison with six reference substances, the Koc of the substance was calculated as 1009.48 at 21.1°C.

The Log Koc of the test substance was therefore approximately 3.