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Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 November 2015 to 9 September 2016
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
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
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Radiolabelling:
no
Test temperature:
The test temperature was 25 °C
Details on study design: HPLC method:
HPLC EQUIPMENT AND EXPERIMENTAL CONDITIONS
Column: Zorbax CN 250 × 4.6 mm with the corresponding guard column
Mobile Phase: Methanol (55 %) and water (45 %), isocratic
Temperature: 25 °C
Flowrate: 1 mL/min
Injection volume: 25 µL
Detection: 210 nm
Run time: 10 minutes (formamide and acetanilide) to 60 minutes (test substance, DDT and mixed standard)

Three standards; formamide (for void volume), acetanilide (the lowest standard, log Koc of 1.25) and DDT (the highest standard, log Koc of 5.63) were used. Two identical runs were performed.

Due to the characteristics of the test substance a value for the adsorption coefficient could not be determined by experimental means.
Key result
Type:
log Koc
Value:
>= 3.007 - <= 4.46 dimensionless
Remarks on result:
other: Calculated estimation of the adsorption Coefficient
Remarks:
(KOCWINMCI method)
Key result
Type:
log Koc
Value:
>= 1.976 - <= 3.524 dimensionless
Remarks on result:
other: Calculated estimation of the adsorption Coefficient
Remarks:
(LKOW method)
Details on results (HPLC method):
ESTIMATION OF THE ADSORPTION COEFFICIENT
Experimental Procedures
Consideration of the chemical structure and physical properties of the test material would lead to difficulties in determining a reliable adsorption coefficient.

A feasibility study was conducted to assess whether or not the HPLC simulation method could be used, as the test material exhibited a strong UV absorbance, albeit at 210 nm. A weak broad peak was observed either between that of formamide (the void marker) and acetanilide or before the formamide peak. This was not thought to be representative of the test material as it is a mixture and a quoted purity of 70 %. The representative chemical structure of the test material provided by the sponsor also indicate low UV chromophore group further supporting that HPLC-UV may not be suitable.

To confirm if the test substance was bound to the column, or not retained, the column was cleaned by first flushing with methanol for 1 hour followed by THF for 1 hour and then water for 1 hour. The system was then left equilibrating overnight with the mobile phase (55 % methanol:45 % water). With the initial methanol wash there was a large amount of contamination driven off. Nothing was recorded for the THF or water washes.

The initial peaks before 3 minutes were present as before but no further peaks were seen.

Under these conditions it can be assumed that the test material was not retained on the column.

It was concluded that on this basis the adsorption coefficient could not be estimated practically. Based on this it was decided calculate adsorption coefficient values using the Estimation Program Interface EPI ver. 4.1.


Calculated values
Calculated values for the log Koc were determined for each of the specified constituents of the test substance stated in information provided by the Sponsor.
The EPI ver 4.1 software used two different methods for calculating the adsorption coefficient, the KOCWIN-MCI and LKOW methods. The calculated values for log Koc from these two methods were as follows:

- KOCWIN-MCI calculated values ranged from 3.0072 for (E)-2-(nonenyl)butane-1,4-dioic acid to 4.4604 for (E)-2-(pentadecenyl)butane-1,4-dioic acid.
- The LKOW calculated values ranged from 1.9755 for (E)-2-(nonenyl)butane-1,4-dioic acid to 3.5243 for (E)-2-(pentadecenyl)butane-1,4-dioic acid.

To test whether or not the test material was retained on the column, the following gradient was applied:

Time

(minutes)

Methanol

(%)

Water

(%)

0

55

45

60

55

45

70

100

0

130

100

0

140

55

45

150

55

45

Calculated Values for Adsorption Coefficient

Common name

log Koc

Test material

3.7338 (KOCWIN-MCI)

2.7499 (LKOW)

(nonenyl)succinic acid

3.0072 (KOCWIN-MCI)

1.9755 (LKOW)

(decenyl)succinic acid

3.2876 (KOCWIN-MCI)

2.2466 (LKOW)

(undecenyl)succinic acid

3.5483 (KOCWIN-MCI)

2.5176 (LKOW)

(tridecenyl)succinic acid

4.0142 (KOCWIN-MCI)

3.0209 (LKOW)

(tetradecenyl)succinic acid

4.2749 (KOCWIN-MCI)

3.2920 (LKOW)

(pentadecenyl)succinic acid

4.4604 (KOCWIN-MCI)

3.5243 (LKOW)

Validity criteria fulfilled:
yes
Conclusions:
The calculated estimation of the adsorption coefficient (Log Koc) ranged from 3.0072 to 4.4604 (KOCWIN-MCI method) and 1.9755 to 3.5243 (LKOW method).
Executive summary:

The adsorption coefficient of the test material was investigated in a study which was performed under GLP conditions and in accordance with the standardised guideline OECD 121 (Calculation).

Consideration of the chemical structure and physical properties of the test material would lead to difficulties in determining a reliable adsorption coefficient therefore a feasibility study was conducted to assess whether or not the HPLC simulation method could be used. Due to the characteristics of the test substance a value for the adsorption coefficient could not be determined by experimental means. It was therefore decided that estimated values would be calculated using appropriate software (Estimation Program Interface EPI ver. 4.1.)

The calculated estimation of the adsorption coefficient (Log Koc) ranged from 3.0072 to 4.4604 (KOCWIN-MCI method) and 1.9755 to 3.5243 (LKOW method).

Endpoint:
adsorption / desorption: screening
Remarks:
Further information on adsorption/desorption
Data waiving:
study technically not feasible
Justification for data waiving:
other:

Description of key information

The calculated estimation of the adsorption coefficient (Log Koc) ranged from 3.0072 to 4.4604 (KOCWIN-MCI method) and 1.9755 to 3.5243 (LKOW method).

Key value for chemical safety assessment

Additional information

The adsorption coefficient of the test material was investigated in a study which was performed under GLP conditions and in accordance with the standardised guideline OECD 121 (Calculation). The study was assigned a reliability score of 2 in accordance with the criteria for assessing data quality set forth by Klimisch et al. (1997).

Consideration of the chemical structure and physical properties of the test material would lead to difficulties in determining a reliable adsorption coefficient therefore a feasibility study was conducted to assess whether or not the HPLC simulation method could be used. Due to the characteristics of the test substance a value for the adsorption coefficient could not be determined by experimental means. It was therefore decided that estimated values would be calculated using appropriate software (Estimation Program Interface EPI ver. 4.1.)

The calculated estimation of the adsorption coefficient (Log Koc) ranged from 3.0072 to 4.4604 (KOCWIN-MCI method) and 1.9755 to 3.5243 (LKOW method).

For the chemical safety assessment since all of the constituents are present in variable ranges in the test substance, the log Koc values were normalized to 100% based on the highest values of the percentages ranges for all constituents and based on the log Koc values calculated using theKOCWIN-MCI method (as this method is more robust than the LKOW method).Therefore the resulting weighted average log Koc is 3.79 (see table below).

Constituent common name

Percentage range [%]

Log Koc

Maximum adjusted percentage [%]

Log Koc component

(tetrapropenyl)succinic acid

50-85

3.7338

53.46

2.00

(nonenyl)succinic acid

0-2

3.0072

1.26

0.04

(decenyl)succinic acid

3-7

3.2876

4.40

0.14

(undecenyl)succinic acid

10-25

3.5483

15.72

0.56

(tridecenyl)succinic acid

0-20

4.0142

12.58

0.50

(tetradecenyl)succinic acid

0-15

4.2749

9.43

0.40

(pentadecenyl)succinic acid

0-5

4.4604

3.14

0.14

 

 

 

 

 

Weighted average

 

 

 

3.79

 

[LogKoc: 3.79]