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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:
Report date: 2012-11-13
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented study performed according to relevant guidelines.
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))
Deviations:
no
GLP compliance:
no
Type of method:
HPLC estimation method
Media:
soil/sewage sludge
Test temperature:
Column temperature: 40 deg C
Details on study design: HPLC method:
Principle of the method:
HPLC is performed on analytical columns packed with commercially available cyanopropyl solid phase containing lipophilic and polar moieties. A moderately polar stationary phase based on silica matrix is used. While passing through the HPLC column along with the mobile phase the test substance interacts with the stationary phase. As a result of partitioning between mobile and stationary phases the test substance is retarded.

Procedure
The distribution coefficient was estimated by the HPLC method using isocratic elution. The HPLC system was calibrated for log k' versus log Koc using reference substances of known log Koc. Test substance was dissolved in tetrahydrofurane. Calibration solutions were prepared in acetonitrile.
Test substance solution: 10.7 mg in 3 ml tetrahydrofurane, filtered through 0.45 μm PTFE membrane filter.
Calibration solutions: approx. 2-13 µg/ml in acetonitrile
Dead time marker: sodium nitrate

Instrumental conditions
HPLC instrument: Agilent 1100
Injection volume: 2 μl test substance solution; 2 µl calibration solution; reference substances see table under "any other informations on materials and methods inc. tables"
Detector: UV, 220 nm
Column: μBondapak CN, 150 mm x 3.1 mm, 10 μm
Mobile phase: water/methanol = 45/55 (v/v)
Flow rate: 0.8 ml/min
Column temperature: 40 deg C

Evaluation of results performed according to the guideline.
Key result
Type:
log Koc
Value:
5.3
Temp.:
40 °C
Remarks on result:
other: Determined by HPLC method, Column temperture 40 deg C
Details on results (HPLC method):
Calibration line and evaluation:
From the calibration line log K' versus log Koc the following equation was calculated:
Y = 0.133x-0.0791, with R^2 = 0.9902

For the test substance, k' was determined as 4.28, log k' = 0.63

From this, the log Koc of the test substance was estimated as follows:

log Koc = (log(k') - b)/a = [0.63 - (-0.0791)]/0.1330 = 5.3

Analytical data:

Substance

log Koc
value

Inj. 1
t
R[min]

Inj. 2
t
R[min]

k'

log k'

mass on
column
[ng]

Sodium nitrate

---

1.007

1.008

---

---

20

Acetanilide

1.25

2.239

2.237

1.22

0.09

20

Phenol

1.32

2.235

2.234

1.22

0.09

16

Methylbenzoate

1.8

2.432

2.43

1.41

0.15

20

Carbendazim

2.35

2.883

2.9

1.87

0.27

*

Naphthalene

2.75

3.009

3.006

1.99

0.3

4

1,2,3-Trichlorobenzene

3.16

3.07

3.071

2.05

0.31

26

Phenanthrene

4.09

3.966

3.963

2.93

0.47

8

4,4'-DDT solution

(100 ng/μl)

5.63

5.721

5.704

4.67

0.67

10

Test substance

---

5.32

5.324

4.28

0.63

*

*: cannot be calculated due to undissolved parts of test substance

Validity criteria fulfilled:
yes
Conclusions:
In a reliable study using the HPLC-method according to OECD 121 for estimating the adsorption coefficient Koc on soil and sewage sludge, for the test item a log Koc of 5.3 was determined. The calculated log Koc value of the test substance is within the calibrated range. 4,4'-DDT was the reference substance with highest log Koc value (5.63).
Executive summary:

The sorption behaviour (log Koc) of the test substance on soil and on sewage sludge was estimated using high performance liquid chromatography (HPLC) according to the OECD Guideline for the Testing of Chemicals 121 (2001; reliability category 1). 8 compounds with log Koc-values between 1.25 and 5.63 were used for calibration. From the capacity factor k' of 4.28 for the test item and the calibration curve a log Koc of 5.3 was determined. The calculated log Koc value of the test substance is within the calibrated range. 4,4'-DDT was the reference substance with highest log Koc value (5.63).

Description of key information

In a study using the HPLC-method according to OECD 121 for estimating the adsorption coefficient Koc on soil and sewage sludge, for the test item a log Koc of 5.3 was determined. The calculated log Koc value of the test substance is within the calibrated range. 4,4'-DDT was the reference substance with highest log Koc value (5.63).

Key value for chemical safety assessment

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