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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 02 February 2017 to 14 March 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
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
Test material information:
Composition 1
Radiolabelling:
no
Test temperature:
Column temperature: 35°C ± 1°C
Details on study design: HPLC method:
PKA CALCULATION
pKa acidic: 13.5; pKa basic: none (Perrin calculation method for the logarithm range of 1 - 14, pKalc 5.0, module in Pallas 3.0, CompuDrug International, USA).

HPLC CONDITIONS
- Apparatus: Acquity UPLC system (Waters, USA)
- Detector: Acquity UPLC PDA (Waters)
- Column: Acquity UPLC HSS Cyano, 100 mm x 2.1 mm i.d., dp = 1.8 µm (Waters)
- UV detection: 210 nm
- Injection volume: 5 μL

MOBILE PHASE
- Type: unbuffered mobile phase
- Composition: 55/45 (v/v) methanol/water
- Flow: 0.4 mL/min

DETERMINATION OF DEAD TIME
- Method: by inert substance which is not retained by the column
- A solution of formamide was prepared in 55/45 (v/v) methanol/water from a stock solution in methanol.

REFERENCE SUBSTANCES
- Identity: Acetanilide, Monuron, 2,5-Dichloroaniline, Naphthalene, Benzoic acid phenylester, Fenthion, Phenanthrene and 4,4’-DDT
- Solutions of the reference substances were prepared in 55/45 (v/v) methanol/water from stock solutions in methanol.

TEST ITEM
- A 10 mg/L test solution in 55/45 (v/v) methanol/water was prepared from a stock solution in methanol.
- All solutions containing the substance were protected from light.

DETERMINATION OF RETENTION TIMES
- Duplicate injections of the unretained substance, reference substances and test item solutions.
- Single injection of the blank solution (55/45 (v/v) methanol/water).

DATA HANDLING
- Dead time (t0) = mean retention time of the unretained substance
- Calculation of capacity factor k' of each compound from its retention time : k' = (tr-t0)/t0
- Log k’ values (references substances) were plotted against their known log Koc values using linear regression analysis (least squares method).
- Log Koc of the substance was calculated by substituting its mean log k’ in the regression line (log k' vs log Koc).
Key result
Type:
log Koc
Value:
4.07 dimensionless
Temp.:
20 °C
Remarks on result:
other: non-buffered mobile phase
Details on results (HPLC method):
- Retention times of reference substances used for calibration: see table below
- Details of fitted regression line (log k' vs. log Koc): log k’ = 0.330 log Koc– 0.791 (r=0.98, n=16)
- Graph of regression line attached
- The chromatogram of the test substance showed one substance peak.
- Average retention data for test substance: see table below
- The value of log Koc obtained from duplicate measurements was within ± 0.25 log units.

Table: Results Adsorption coefficient (HPLC estimation method)

Substance

RT1[min]

RT2[min]

Mean RT [min]

log Koc#

Koc

 

 

 

 

 

 

Formamide (t0)

0.670

0.671

0.671

 

 

 

 

 

 

 

 

Acetanilide

0.909

0.911

 

1.26

 

Monuron

1.141

1.145

 

1.99

 

2,5-Dichloroaniline

1.328

1.323

 

2.55

 

Naphthalene

1.559

1.554

 

2.75

 

Benzoic acid phenylester

1.858

1.858

 

2.87

 

Fenthion

2.572

2.559

 

3.31

 

Phenanthrene

2.852

2.845

 

4.09

 

4,4’-DDT

7.502

7.454

 

5.63

 

 

 

 

 

 

 

Test item

3.056

3.033

3.045

4.07

1.2 E04

# log Koc values of the reference substances according to OECD 121 (based on soil adsorption data).

Validity criteria fulfilled:
yes
Remarks:
Test has been performed according to the guideline
Conclusions:
The log Koc of the substance was estimated to be 4.07 (Koc= 1.2E04).


Executive summary:

The HPLC estimation method based on soil-adsorption reference data was used for the determination of the adsorption coefficient (Koc) of the substance. The study was performed in accordance with OECD 121 and in compliance with GLP. The mobile phase was 55/45 (v/v) methanol/water and the wavelength of detection 210 nm. The stationary phase contained cyanopropyl chains chemically bonded to silica. Formamide was used as unretained substance. Duplicate injections of reference substances and test substance. The chromatogram of the test substance showed one test substance peak. The corresponding log Koc value was calculated from the regression line to be 4.07 (Koc= 1.2E04).

Description of key information

The HPLC estimation method based on soil-adsorption reference data was used for the determination of the adsorption coefficient (Koc) of the substance. The study was performed in accordance with OECD 121 and in compliance with GLP. The mobile phase was 55/45 (v/v) methanol/water and the wavelength of detection 210 nm. The stationary phase contained cyanopropyl chains chemically bonded to silica. Formamide was used as unretained substance. Duplicate injections of reference substances and test substance. The chromatogram of the test substance showed one test substance peak. The corresponding log Koc value was calculated from the regression line to be 4.07 (Koc= 1.2E04).

Key value for chemical safety assessment

Koc at 20 °C:
12 000

Additional information