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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
November 27th, 2012 - April 7th, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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))
Version / remarks:
(2008)
Deviations:
no
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))
Version / remarks:
(2001)
Deviations:
no
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil
Radiolabelling:
no
Details on study design: HPLC method:
CALCULATION OF pKa:
The following pKa values in the pH range of 1 - 14 were calculated using the Perrin calculation method (pKalc 5.0, module in Pallas 3.0, CompuDrug International San Francisco, USA):

2,2’-[(4-methylphenyl)imino]-diethanol: acidic (none); basic: RARN(R1R2): pKa 4.02
2-{[2-(2-hydroxyethoxy)ethyl](4-methylphenyl)amino}ethanol: acidic (none); basic: RARN(R1R2): pKa 3.94

HPLC METHOD CONDITIONS:
Instrument: Acquity UPLC system (Waters, Milford, MA, USA)
Detector: Acquity UPLC TUV detector (Waters)
Column: Acquity UPLC HSS, 50 mm x 2.1 mm i.d., dp = 1.8 µm (Waters)
Column temperature: 35°C ± 1°C
Mobile phase: 30/70 (v/v) methanol/water
Flow : 0.4 mL/min
Injection volume: 5 μL
UV detection: 210 nm

REFERENCE SUBSTANCES: acetanilide; Monuron; 2,5-dichloroaniline; benzoic acid phenylester and Fenthion
Unretained compound: Formamide
 
PREPARATION OF SOLUTIONS:
Solution of the unretained compound
A 5.22 g/L stock solution of formamide in methanol was used. The stock solution was diluted to obtain an end solution of 30/70 (v/v) methanol/water. The formamide blank solution was 30/70 (v/v) methanol/water.

Reference substance solutions
Stock solutions of the reference substances at concentrations of approximately 1 g/L in methanol were used. The stock solutions were diluted to obtain an end solution of 30/70 (v/v) methanol/water. The blank solution for the reference substance solutions was 30/70 (v/v) methanol/water.

Test solution
A 2180 mg/L stock solution of the test substance was prepared in methanol. The stock solution was diluted to obtain an end solution of 30/70 (v/v) methanol/water. The final concentration of the test substance solution was 9.98 mg/L. The test substance blank solution was 30/70 (v/v) methanol/water.

The reference substance and test substance solutions were injected in duplicate. Blank solutions were analysed by single injection.

PERFORMANCE OF THE STUDY
Solutions of reference substances with known log Koc values based on soil adsorption data and the test substance were analysed. The capacity factor (k') of each compound was calculated from its retention time. The log k’ values of the references substances were plotted against the known log Koc values. A linear regression program was used to calculate the calibration curve. Linear regression analysis was performed using the least squares method. The coefficient of correlation (r) was calculated. The log Koc value for the test substance was calculated by substituting its mean log k’ in the calibration curve: log k’ = 0.709 x log Koc – 0.978 (r = 0.94, n = 12). The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.
Analytical monitoring:
yes
Type:
log Koc
Value:
2.22 dimensionless
Temp.:
35 °C
Remarks on result:
other: Peak area 52%
Type:
log Koc
Value:
2.44 dimensionless
Temp.:
35 °C
Remarks on result:
other: Peak area 38%
Type:
log Koc
Value:
2.51 dimensionless
Temp.:
35 °C
Remarks on result:
other: Peak area 4.9%
Type:
log Koc
Value:
2.67 dimensionless
Temp.:
35 °C
Remarks on result:
other: Peak area 2.4%
Key result
Type:
log Koc
Value:
2.33 dimensionless
Temp.:
20 °C
Remarks on result:
other: weight-averaged value based on four main components covering 97.3% (by area-%) of the whole substance (Koc = 214)
Details on results (HPLC method):
In the HPLC chromatogram of the test substance, a total number of 18 peaks have been identified from which four peaks with retention times of 3.47 min. (52% peak area), 4.65 min. (38% peak area), 5.17 min. (4.9% peak area) and 6.46 min. (2.4% peak area) were observed. Under the same conditions, the retention time of benzoic acid phenylester (log Koc 2.87) was 10.55 - 10.53 minutes.
Transformation products:
not measured

Table: Measurements and results for the Koc determination:

Substance

mean tr
(n=2)

log Koc

Koc

Area
%

 

 

 

 

 

Formamide (t0)

0.703

 

 

 

 

 

 

 

 

Acetanilide

 

1.26

 

 

Monuron

 

1.99

 

 

2,5-Dichloroaniline

 

2.55

 

 

Naphthalene

 

2.75

 

 

Benzoic acid phenylester

 

2.87

 

 

Fenthion

 

3.31

 

 

 

 

 

 

 

peak 1

1.316

1.30

2.0´101

0.032

peak 2

1.571

1.51

3.2´101

0.30

peak 3

1.836

1.67

4.7´101

0.85

peak 4

2.237

1.86

7.2´101

0.44

peak 5

2.366

1.91

8.1´101

0.060

peak 6

2.614

1.99

9.8´101

0.012

peak 7

2.781

2.04

1.1´102

0.021

peak 8

3.285

2.18

1.5´102

0.0054

peak 9

3.469

2.22

1.7´102

52

peak 10

4.647

2.44

2.7´102

38

peak 11

5.174

2.51

3.2´102

4.9

peak 12

6.035

2.62

4.2´102

0.058

peak 13

6.271

2.65

4.4´102

0.046

peak 14

6.464

2.67

4.6´102

2.4

peak 15

7.104

2.73

5.4´102

0.36

peak 16

9.456

2.92

8.4´102

0.024

peak 17

9.583

2.93

8.6´102

0.084

peak 18

9.926

2.96

9.0´102

0.058

 

 

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
The HPLC method (in accordance with EC C.19 and OECD 121 and in compliance with GLP) was performed to determine the adsorption coefficient (soil) of the test substance. The HPLC chromatogram of the test solution showed four major peaks (with peak areas of 52%, 38%, 4.9% and 2.4%). The log Koc for the major peaks were 2.22, 2.44, 2.51 and 2.67, respectively. The weight-averaged logKoc value considering the four main components has been derived to be 2.33 (= log 214). HPLC column temperature: 35°C ± 1°C, but the log Koc of reference substances have been determined at 20 °C, thus the 2.33 value is determined as well for 20 °C.

Description of key information

The weight-averaged logKoc value considering the four main components has been derived to be 2.33 (= log 214).

Key value for chemical safety assessment

Koc at 20 °C:
214

Additional information

The HPLC method (in accordance with EC C.19 and OECD 121 and in compliance with GLP) was performed to determine the adsorption coefficient (soil) of the test substance. The HPLC chromatogram of the test solution showed four major peaks (with peak areas of 52%, 38%, 4.9% and 2.4%). The log Koc for the major peaks were 2.22, 2.44, 2.51 and 2.67, respectively.

The weight-averaged logKoc value considering the four main components has been derived to be 2.33 (= log 214). HPLC column temperature: 35°C ± 1°C, while it is considered that the Koc values of the reference substances, as reported in the OECD 121, have been determined at 20 °C.

[LogKoc: 2.33]