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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From November 16, 2017 to November 29, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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)
Key result
Sample No.:
#1
Type:
log Koc
Value:
< 1.32 dimensionless
Temp.:
25 °C

Results:

Referencesubstances:

Measurement data: Retention times (RT) reference substances

Compound

RT1

RT2

RT3

RT4

RT5

RT6

 

min.

min.

min.

min.

min.

min.

Sodium nitrate

1.015

1.017

1.017

1.053

1.040

1.042

Phenole

2.879

2.879

2.877

2.877

2.877

2.877

Methylbenzoate

3.247

3.245

3.242

3.240

3.242

3.240

Naphthaline

5.075

5.070

5.060

5.060

5.064

5.064

1,2,3-Trichlorbenzene

6.194

6.184

6.167

6.165

6.169

6.169

Phenanthrene

9.130

9.107

9.085

9.090

9.102

9.107

4,4’-DDT

24.185

24.035

23.955

23.978

24.042

24.069

 

Calculated values: The capacity factors k’ were calculated from the retention times using the equatio. The values are given in the following table.

Mean retention times (RT), capacity factors reference substances

Compound

RT
Mean

RT
Standard
Deviation

RT
Relative Standard
Deviation

k’

 

min.

min.

%

 

Sodium nitrate

1.031

0.016

1.598

0.0000

Phenole

2.877

0.001

0.032

1.7917

Methylbenzoate

3.243

0.003

0.086

2.1461

Naphthaline

5.065

0.006

0.120

3.9147

1,2,3-Trichlorbenzene

6.174

0.012

0.187

4.9906

Phenanthrene

9.103

0.016

0.174

7.8326

4,4’-DDT

24.044

0.081

0.337

22.3286

 

  

log KOC/ log k’

The log KOCvalues of the reference substances were taken from the guideline. The values for log k’ and log KOCof the reference substances are presented in the following table:

Log k’ and log KOCof reference substances

Compound

log k’

log KOC

Phenole

0.2533

1.32

Methylbenzoate

0.3317

1.80

Naphthaline

0.5927

2.75

1,2,3-Trichlorbenzene

0.6981

3.16

Phenanthrene

0.8939

4.09

4,4’-DDT

1.3489

5.63

 

Correlation results

Dead time is 1.031 ± 0.016 minutes, with a RSD of 1.598%.

The RSD of the retention times of the reference substances lay all below 1% except for sodium nitrate (RSD of retention times 1.598%).

Equation of the regression:

log k’ = 0.2546 * logKOC– 0.1091
with a coefficient of determination r2
 = 0.9962

 

Test substance

Measurement data: Retention times (RT) test substance

Measurement

RT 1

RT 2

RT 3

 

min.

min.

min.

Measurement 1

1.715

1.805

2.097

Measurement 2

1.737

1.827

2.100

Measurement 3

1.767

1.922

2.097

Mean

1.740

1.851

2.098

Standard Deviation

0.026

0.062

0.002

 

 

Peak areas test substance

Measurement

Area

Peak 1

Relative Area
Peak 1

Area

Peak 2

Relative Area
Peak 2

 

mAU*min

%

mAU*min

%

Measurement 1

0.5345 

85.53

0.0616 

9.86

Measurement 2

0.6010 

88.60

0.0520 

7.67

Measurement 3

0.6211 

90.97

0.0369 

5.41

Mean

0.586 

88.37 

0.050 

7.64 

Relative Standard Deviation

7.7%

3.1%

24.8%

29.1%

Measurement

Area

Peak 3

Relative Area
Peak 3

 

 

mAU*min

%

 

Measurement 1

0.0288 

4.61

 

Measurement 2

0.0253 

3.73

 

Measurement 3

0.0248 

3.63

 

Mean

0.026 

3.99 

 

Relative Standard Deviation

8.3%

13.5%

 

As peak 3 showed a relative area < 5%, this peak was considered as minor peak.

 

Calculated values:The calculated values are presented in the following table:

Capacity Factor, log capacity factor, log KOCtest substance

Peak 1 Test Substance

k’

log k’

log KOC

Measurement 1

0.6640

-0.1779

-0.270

Measurement 2

0.6852

-0.1642

-0.216

Measurement 3

0.7143

-0.1461

-0.145

Mean

 

 

-0.210

Standard deviation

 

 

0.062

 

 

Peak 2 Test Substance

k’

log k’

log KOC

Measurement 1

0.7513

-0.1242

-0.059

Measurement 2

0.7725

-0.1121

-0.012

Measurement 3

0.8647

-0.0632

0.181

Mean

 

 

0.037

Standard deviation

 

 

0.127

 

Peak 3 Test Substance

k’

log k’

log KOC

Measurement 1

1.0343

0.0146

0.486

Measurement 2

1.0377

0.0161

0.492

Measurement 3

1.0344

0.0147

0.487

Mean

 

 

0.488

Standard deviation

 

 

0.003

log KOCwas calculated from the capacity factor as follows:

log KOC= (log k’ + 0.1091) / 0.2546

 

Result and validity:

As peak 3 showed a relative area < 5 %, this peak was considered as minor peak. Although area is not necessarily correlated to absolute concentration if a UV detector is used, it is assumed that the test substance consists mainly of the peaks 1 and 2. All peaks of the test substance solution lay after sodium nitrate, used for the determination of the dead time, and before the first reference substance phenol. Using the correlation log k’ / log KOC, the log KOCof the peaks of the test substance was calculated as -0.210 – 0.037 (peak 1 and 2). Due to the fact that the calculated log KOCof the test substance lay outside the calibrated range (1.32 – 5.63), the log KOCof the test substance is stated as < 1.32.

  

Validity criteria and Results

Peak

Parameter

Criterion

Found

Assessment

1

Range (Max – Min. log KOC)

< 0.25

0.125

valid

Value within Range of Reference Substances

1.32 - 5.63

-0.210

not valid*

2

Range (Max – Min. log KOC)

< 0.25

0.240

valid

Value within Range of Reference Substances

1.32 - 5.63

0.037

not valid*

3

Range (Max – Min. log KOC)

< 0.25

0.006

valid

Value within Range of Reference Substances

1.32 - 5.63

0.488

not valid*

* The calculated log KOCof the test substance peaks lay outside the calibrated range (1.32 – 5.63), because the peaks eluted in the dead time of the method.

 

 

Validity criteria fulfilled:
yes
Conclusions:
Under study conditions, the log Koc value of the test substance for soil and sewage sluge was determined to be <1.32 at 25 ± 0.5˚C.
Executive summary:

A study was conducted to determine the adsorption coefficient (log Koc) of the substance on soil and on sewage sludge according to OECD Guideline 121, in compliance with GLP. In the study, measured HPLC retention data were obtained for 7 reference substances (i.e., sodium nitrate, phenol, methylbenzoate, naphthalene, 1,2,3-Trichlorobenzene,  phenanthrene and 4,4' DDT). A solvent blank followed by three injections of a solution of the reference substances were analysed with HPLC; then three injections of a solution of the test substance; and finally three injections of the solution with the reference substances, in total ten runs. For each reference substance, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference substance. A calibration function was set up using the literature values for Koc of the reference substances and the mean capacity factor of the six determinations. In the graph log k’ versus log Koc, linear regression was performed, resulting in r2= 0.9962. The chromatogram of the test substance gave 1 large and 2 small peaks after sodium nitrate, used for the determination of the dead time, and before the first reference substance phenol. As peak 3 showed a relative area < 5 %, this peak was considered as minor peak. Although area is not necessarily correlated to absolute concentration if a UV detector is used, it is assumed that the test substance consists mainly of the peaks 1 and 2. Using the correlation log k’ / log Koc, the log Kocof the peaks of the test substance was calculated as -0.210 – 0.037 (peak 1 and 2). Due to the fact that the calculated log Koc of the test substance lay outside the calibrated range ( log Koc :1.32 – 5.63), the log Koc of the test substance was determined to be <1.32. Under study conditions, the log Koc of the test substance, for soil and sewage sludge was determined to be <1.32 at 25 ± 0.5˚C (Brinkmann, 2018).

Description of key information

Key value for chemical safety assessment

Koc at 20 °C:
1.32

Additional information

A study was conducted to determine the adsorption coefficient (log Koc) of the substance on soil and on sewage sludge according to OECD Guideline 121, in compliance with GLP. In the study, measured HPLC retention data were obtained for 7 reference substances (i.e., sodium nitrate, phenol, methylbenzoate, naphthalene, 1,2,3-Trichlorobenzene,  phenanthrene and 4,4' DDT). A solvent blank followed by three injections of a solution of the reference substances were analysed with HPLC; then three injections of a solution of the test substance; and finally three injections of the solution with the reference substances, in total ten runs. For each reference substance, the capacity factor k’ was calculated from the retention time of sodium nitrate and the retention time of the respective reference substance. A calibration function was set up using the literature values for Koc of the reference substances and the mean capacity factor of the six determinations. In the graph log k’ versus log Koc, linear regression was performed, resulting in r2= 0.9962. The chromatogram of the test substance gave 1 large and 2 small peaks after sodium nitrate, used for the determination of the dead time, and before the first reference substance phenol. As peak 3 showed a relative area < 5 %, this peak was considered as minor peak. Although area is not necessarily correlated to absolute concentration if a UV detector is used, it is assumed that the test substance consists mainly of the peaks 1 and 2. Using the correlation log k’ / log Koc, the log Koc of the peaks of the test substance was calculated as -0.210 – 0.037 (peak 1 and 2). Due to the fact that the calculated log Koc of the test substance lay outside the calibrated range ( log Koc :1.32 – 5.63), the log Koc of the test substance was determined to be <1.32. Under study conditions, the log Koc of the test substance, for soil and sewage sludge was determined to be <1.32 at 25 ± 0.5˚C (Brinkmann, 2018).