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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
27-May-2010 to 31-Aug-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
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
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. QA statement)
Remarks:
Date of Certificate: November 12, 2008
Type of method:
HPLC estimation method
Media:
other: not applicable
Radiolabelling:
no
Test temperature:
25 °C
Details on study design: HPLC method:
HPLC-Conditions

Methanol was found to be not suitable to elute Dilauroyl peroxide (CAS# 105-74-8). Referring to this, tetrahydrofuran was used as organic solvent.

Apparatus: Varian autosampler 9095
Varian pump 9012
Varian UV/VIS detector ProStar 310
Croco-Cil column oven LCSOF 55
Column: LiChrospher 100 CN, particle size 5 µm, 250 mm x 4 mm
HPLC Eluent: Water / tetrahydrofuran (45:55; v/v); pH 5.90
Detection: Test item: 210 nm
Reference item: 210 nm
Sodium nitrate: 210 nm
Temperature: 25 °C
Injection Volume: 20 µL
Flow: 1.0 mL/min
Run Time: 20 minutes
Retention Times: See Table 1

Analytical monitoring:
not required
Type:
Koc
Value:
> 426 580
Temp.:
25 °C
Remarks on result:
other: determined by HPLC method
Type:
log Koc
Value:
> 5.63
Temp.:
25 °C
Remarks on result:
other: determined by HPLC method
Type:
log Koc
Value:
> 7.81
Temp.:
25 °C
Remarks on result:
other: calculated by QSAR
Type:
log Koc
Value:
ca. 8.3
Temp.:
25 °C
Remarks on result:
other: calculated by extrapolation for experimental results
Transformation products:
not measured

In a preliminary test, the stability of the test item was observed. The retention times of the injected test item solution did not differ after 4 hours of alteration compared to the test item solution injected immediately after preparation. Thus, the test item solution was found to be stable during testing.

 

The test item solution of the main test was injected three times and the reference mix solution was injected six times.In the present study the reference items covered the range from log KOC 1.25 to log KOC 5.63.The retention time of the test item is higher than the retention time of the reference item (2,4‑DDT) with the highest log KOC(5.63, which is equal to a KOCvalue of 426580).Therefore, the log KOCof the test item is> 5.63, which is equal to a KOCvalue of> 426580 using the HPLC method. This value indicates that Dilauroyl peroxide (# 105-74-8) is immobile and will be adsorbed by organic carbon in soil.

The Log KOCcan be extrapolated from the regression curve to be 8.3.

 

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 in one peak with a well-defined and reproducible retention time. 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 log k’ was plotted versus KOCfor each component to obtain a regression curve (Table 2 and attached 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)

1.344

1.338

1.344

 

 

 

Reference Items:

Acetanilide

2.921

2.931

2.932

2.923

2.921

2.920

Isoproturon

3.303

3.314

3.315

3.307

3.305

3.303

Linuron

3.572

3.582

3.583

3.576

3.572

3.571

Pyrazophos

4.335

4.344

4.347

4.338

4.335

4.338

Diclofop-methyl

4.911

4.916

4.921

4.914

4.905

4.913

2,4-DDT

5.523

5.523

5.532

5.524

5.512

5.524

Dilauroyl peroxide (CAS# 105-74-8):

 

 

 

TestItemPeak

9.636

9.691

9.667

 

 

 

 

The retention time of the test item peak in all runs is longer than the retention time of 2,4-DDT, the last reference item on the list of the guideline with a log KOCvalue of 5.63.

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)

3

1.34

-

-

 

Reference Items:

Acetanilide

6

2.92

1.18

0.07

1.25

Isoproturon

6

3.31

1.46

0.17

1.86

Linuron

6

3.58

1.66

0.22

2.59

Pyrazophos

6

4.34

2.23

0.35

3.65

Diclofop-methyl

6

4.91

2.66

0.43

4.20

2,4-DDT

6

5.52

3.12

0.49

5.63

 

slope =

 

 

 

0.099

Linear Regression:

y-axis intercept =

-0.028

 

coefficient of regression (r) =

0.986

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
The log of the adsorption coefficient (KOC) of Dilauroyl peroxide (CAS# 105-74-8) was estimated to be log KOC > 5.63 which is equal to a KOC value of > 426580 using the HPLC method. The Log KOC can be extrapolated from the regression curve to be 8.3. The experimentally determined result was confirmed by a model calculation, which results in a value of log KOC > 7.81. The data indicates that Dilauroyl peroxide (CAS# 105-74-8) will be adsorbed by organic carbon in soil. Dilauroyl peroxide (CAS# 105-74-8) is immobile.

Executive summary:

PURPOSE

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 KOC is 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 KOC in soil and sewage sludge.

The log of the adsorption coefficient (KOC) of Dilauroyl peroxide (# 105-74-8) was estimated to be

 

log KOC> 5.63 which is equal to a KOCvalue of >426580

 

using the HPLC method. The retention times after immediately injection and injection after 4 hours did not show significant differences. Thus, the test item solution was found to be stable during testing. The Log KOCcan be extrapolated from the regression curve to be 8.3.

 

The experimentally determined result was confirmed by a model calculation, which results in a value of log KOC > 7.81.

 

The data indicates that Dilauroyl peroxide (# 105-74-8) will be adsorbed by organic carbon in soil. Dilauroyl peroxide (# 105-74-8) can be classified to be immobile according these study results.

Description of key information

The log Koc based on extrapolation of retention times derived experimentally was 8.3. However, this is significantly above the highest reference substance and should be used in the absence of a more accurate value, with caution.

Key value for chemical safety assessment

Koc at 20 °C:
199 526 231

Additional information

An adsorption study was performed using the HPLC method. Using the standard reference values the log Kow was found to be higher than that of the highest reference substance. However various methods were used in complement in order to provide a value. The only method that successfully calculated a value was the use of extrapolated retention times. The log Koc based on this was 8.3 and should be used with caution.

[LogKoc: 8.3]