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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 11 June, 2012 to 14 Sep, 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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))
Version / remarks:
(2008)
Deviations:
no
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))
Version / remarks:
(2001)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
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): pKa acidic: none; pKa basic: none.

HPLC METHOD CONDITIONS
Based on the pKa calculations, the mobile phase was not buffered.

Instrument: Alliance Separation Module 2695 (Waters, USA)
Detector: Dual λ Absorbance Detector 2487 (Waters)
Column: Hypersil-BDS-CN, 150 mm x 4.6 mm i.d., dp= 5 µm (Thermo Fisher Scientific, USA)
Column temperature:  35°C ± 1°C
Mobile phase:  55/45 (v/v) methanol/water
Flow: 1 mL/min
Injection volume: 10 µL
UV detection: 210 nm

REFERENCE SUBSTANCES
Log Koc values based on soil adsorption data (OECD 121):
-Acetanilide, > 99.9%, CAS 103-84-4, log Koc 1.26
-Atrazine, 97.5%, CAS 1912-24-9, log Koc 1.81
-Monuron, 99.9%, CAS 150-68-5, log Koc 1.99
-2,5-Dichloroaniline, 99.8%, CAS 95-82-9, log Koc 2.55
-Benzoic acid phenylester, 99.9%, CAS 93-99-2, log Koc 2.87
-Fenthion, 96.2%, CAS 55-38-9, log Koc 3.31
-Phenanthrene, 98.1%, CAS 85-01-8, log Koc 4.09
-4,4’-DDT, 98.2%, CAS 50-29-3, log Koc 5.63

PREPARATION OF 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 55/45 (v/v) methanol/water.

A 1104 mg/L stock solution of the test substance was prepared in methanol. The stock solution was diluted to obtain a final concentration of 607.2 mg/L. End solution: 55/45 (v/v) methanol/water. All solutions containing the test substance were protected from light

A 5.61 g/L stock solution of the unretained compound formamide (99.8%) in methanol was used. The stock solution was diluted to obtain an end solution of 55/45 (v/v) methanol/water.

PERFORMANCE OF THE STUDY
The reference substance and test substance solutions were injected in duplicate. Blank solution (55/45 (v/v) methanol/water) was analysed by single injection. 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 (least squares method). The log Koc value for the test substance was calculated by substituting its mean log k’ in the calibration curve: log k’ = 0.284 x log Koc– 1.10 (r=0.974, n=16). The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.
Key result
Type:
log Koc
Value:
5.63 dimensionless
Remarks on result:
other: Peak area: 10%. Koc = 4.3E5
Key result
Type:
log Koc
Value:
ca. 2.5 dimensionless
Remarks on result:
other: Peak area: 17.4%. Koc= 3.1E2.
Key result
Type:
log Koc
Value:
ca. 3.33 dimensionless
Remarks on result:
other: Peak area: 26.1%. Koc= 2.1E3.
Details on results (HPLC method):
In the HPLC chromatogram of the test solution, two major peaks and several smaller peaks were observed. Measurements and results are summarized in the table below.

Remark: The major components have been assigned based on relative peak area and might not correspond with the major components mentioned in Confidential details on test material.

Chromatogram and calibration curve: see attachment.

Table: Measurements and results for the Koc determination of the test substance:

Substance

tr,1
[min]

tr,2
[min]

mean tr
(n=2)

log Koc

Koc

Area
%

 

 

 

 

 

 

 

Formamide (t0)

1.965

1.965

1.965

 

 

 

 

 

 

 

 

 

 

Acetanilide

2.245

2.245

 

1.26

 

 

Atrazine

2.452

2.454

 

1.81

 

 

Monuron

2.521

2.520

 

1.99

 

 

2,5-Dichloroaniline

2.846

2.843

 

2.55

 

 

Benzoic acid phenylester

3.104

3.104

 

2.87

 

 

Fenthion

4.092

4.089

 

3.31

 

 

Phenanthrene

4.094

4.094

 

4.09

 

 

4,4’-DDT

7.038

7.035

 

5.63

 

 

 

 

 

 

 

 

 

Peak 1

0.784

0.782

0.783

< 1.26

<1.8E1

0.3

Peak 2

0.997

0.994

0.996

< 1.26

<1.8E1

0.1

Peak 3

1.255

1.255

1.255

< 1.26

<1.8E1

0.1

Peak 4

1.717

1.718

1.718

< 1.26

<1.8E1

1.4

Peak 5

1.972

1.973

1.973

< 1.26

<1.8E1

2.2

Peak 6

2.223

2.222

2.223

< 1.26

<1.8E1

1.6

Peak 7

2.428

2.424

2.426

1.65

4.5E1

6.7

Peak 8

2.625

2.623

2.624

2.20

1.6E2

2.2

Peak 9 (major component 1)

2.768

2.766

2.767

2.50

3.1E2

17.4

Peak 10

2.905

2.902

2.904

2.74

5.4E2

6.6

Peak 11 (major component 2)

3.349

3.347

3.348

3.33

2.1E3

26.1

Peak 12

3.566

3.564

3.565

3.55

3.6E3

7.4

Peak 13

3.841

3.839

3.840

3.79

6.2E3

2.0

Peak 14

4.001

3.998

4.000

3.92

8.3E3

2.6

Peak 15

4.284

4.279

4.282

4.12

1.3E4

1.6

Peak 16

4.526

4.523

4.525

4.27

1.9E4

0.5

Peak 17

4.726

4.722

4.724

4.38

2.4E4

0.6

Peak 18

5.074

5.072

5.073

4.57

3.7E4

5.1

Peak 19

5.509

5.506

5.508

4.77

5.8E4

2.6

Peak 20

5.959

5.956

5.958

4.95

8.9E4

1.2

Peak 21

6.396

6.393

6.395

5.11

1.3E5

0.8

Peak 22

6.897

6.894

6.896

5.27

1.9E5

4.0

Peak 23

7.576

7.574

7.575

> 5.63

> 4.3E5

2.2

Peak 24

8.385

8.383

8.384

> 5.63

> 4.3E5

1.8

Peak 25

9.254

9.250

9.252

> 5.63

> 4.3E5

1.4

Peak 26

12.218

12.217

12.218

> 5.63

> 4.3E5

1.0

Peak 27

13.611

13.600

13.606

> 5.63

> 4.3E5

0.5

Conclusions:
Under the study conditions: (a) At neutral pH, the log Koc values for the two major peaks were 2.50 and 3.33 (Koc: 3.1E+2 and 2.1E+3), respectively (b) At neutral pH, the log Koc values for the 25 minor peaks (<10%) ranged from < 1.26 to > 5.63 (Koc ranges from < 18 to > 4.3E+5).
Executive summary:

A study was conducted to determine the adsorption/desorption coefficient of the test substance, DPHA, according to OECD Guideline 121 and EU Method C.9, using the HPLC method at neutral pH, in compliance with GLP. According to the guidelines, the determination of the Koc for test substances that are ionized for at least 10% within pH 5.5 to 7.5 should be performed with both the ionized and non-ionized form. Therefore, the pKa values of the test substance were calculated using the Perrin calculation method. Based on the calculations, the HPLC analysis was performed at neutral pH. 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. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units. No pKa values were calculated in the logarithm range of 1 – 14 for acidic and basic groups in the molecular structure of both main components of the test substance using the Perrin calculation method. In the chromatogram of the test solution, several test substance peaks were observed. Under the study conditions: (a) At neutral pH, the log Koc values for the two major peaks were 2.50 and 3.33 (Koc: 3.1E+2 and 2.1E+3), respectively (b)  At neutral pH, the log Koc values for the 25 minor peaks (<10%) ranged from < 1.26 to > 5.63 (Koc ranges from < 18 to > 4.3E+5) (Lammers, 2012).

Description of key information

Based on the study results: (a) At neutral pH, the log Koc values for the two major peaks were 2.50 and 3.33 (Koc: 3.1E+2 and 2.1E+3), respectively (b)  At neutral pH, the log Koc values for the 25 minor peaks (<10%) ranged from < 1.26 to > 5.63 (Koc ranges from < 18 to > 4.3E+5).

Key value for chemical safety assessment

Koc at 20 °C:
430 000

Additional information

A study was conducted to determine the adsorption/desorption coefficient of the test substance, DPHA, according to OECD Guideline 121 and EU Method C.9, using the HPLC method at neutral pH, in compliance with GLP. According to the guidelines, the determination of the Koc for test substances that are ionized for at least 10% within pH 5.5 to 7.5 should be performed with both the ionized and non-ionized form. Therefore, the pKa values of the test substance were calculated using the Perrin calculation method. Based on the calculations, the HPLC analysis was performed at neutral pH. 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. The value of log Koc obtained from duplicate measurements was within ± 0.25 log units. No pKa values were calculated in the logarithm range of 1 – 14 for acidic and basic groups in the molecular structure of both main components of the test substance using the Perrin calculation method. In the chromatogram of the test solution, several test substance peaks were observed. Under the study conditions: (a) At neutral pH, the log Koc values for the two major peaks were 2.50 and 3.33 (Koc: 3.1E+2 and 2.1E+3), respectively (b)  At neutral pH, the log Koc values for the 25 minor peaks (<10%) ranged from < 1.26 to > 5.63 (Koc ranges from < 18 to > 4.3E+5) (Lammers, 2012).