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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Study period:
September 3rd to 4th 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, carried out according to recognised guideline
Reason / purpose:
reference to same 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)
Type of method:
HPLC estimation method
Media:
other: HPLC Media
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable.
Radiolabelling:
no
Details on study design: HPLC method:
REAGENTS AND MATERIALS

Methanol: for HPLC, Carlo Erba, Batch No.: V9M706099M
Ultra pure water (ASTM Type I): prepared by Direct-Q 3 system, Millipore

PRINCIPLE OF THE TEST
The method uses HPLC for estimation of the adsorption coefficient, Koc.
The dual composition of the stationary phase having polar and non-polar sites allows for interaction of polar and non-polar groups of a molecule in a similar way, as in the case for organic matter in soil or sewage sludge matrices. This enables the relationship between the retention time on the column and the adsorption coefficient on organic matter to be established.

APPARATUS

Stationary Phase: LiChrospher 100 CN 250 x 4 mm, 5µm HPLC Column

HPLC system:
Merck-Hitachi LaChrom HPLC system:
D-7000 Interface, No.: 1126-175
L-7100 HPLC Pump, No. : 1388-056
L-7200 Autosampler, No.: 1380-033
L-7400 UV Detector, No.: 1374-025
L-7360 Column Oven, No.: 00118060
L-7614 Degasser, No.: 144116A0094
Ultrasonic bath: Elmasonic S300H, ELMA, No.: 010890105
Balance: BP221S Sartorius, No.: 11809117
Water purification system: MILLIPORE, DIRECT Q3, FOMNO 7334I


HPLC Conditions:

Detector: UV at 210 nm
Column: LiChrospher 100 CN 250 x 4 mm, 5µm No.: 540779-1
Mobil Phase: Methanol : Water = 55 : 45
Flow: 1 ml/min.
Injection volume: 10 *l
Temperature: 25 °C

REFERENCE SUBSTANCES

Seven chemicals for which log Koc has been reported were used to calibrate the elution time in units of log Koc.

Dead time, t0 was determined by the injection of sodium nitrate solution. Reference substances used for calibration are detailed in table 1 below:



PERFORMANCE OF THE TEST


Preparation of the Test Solutions:

Reference substances were dissolved in methanol. Concentration of these stock solutions was about 1 mg/ml. These stock solutions were diluted with the mobile phase resulting in about 10 µg/ml solutions.
In case of Sodium nitrate and DDT the stock solutions were diluted with the mobile phase resulting in about 100 ¿g/ml solutions.
¿-Endosulfan was dissolved in eluent and this solution (1 mg/ml) was analysed.
Kronitex TXP was also dissolved in methanol. The concentration of this solution was 1 mg/ml. This stock solution was diluted with mobile phase resulting in about 10 ¿g/ml solutions.

Determination of the retention times:

Three series of the above reference solutions and the test item solution were measured alternately, with two replicate injections.
For the determination of t0 (t0 = retention time of the unretarded component) sodium nitrate solution was injected.
The retention times were determined.

EVALUATION

The capacity factors, k’ were calculated from the retention times (tR) of the selected reference substances and the dead time (t0):

k’= (tR-t0) / t0

A calibration plot of log k' versus log Koc was prepared. The calibration equation was determined by linear regression using the least squares method.
Repeatability is the difference of maximum and minimum values of log Koc derived from individual measurements.
Accuracy is the difference between the estimated log Koc and the log Koc value determined by the batch equilibrium method.

Analytical monitoring:
no
Details on sampling:
Not applicable.
Details on matrix:
Not applicable.
Details on test conditions:
Not applicable.
Computational methods:
Not applicable.
Key result
Type:
log Koc
Value:
5.08 dimensionless
Key result
Type:
Koc
Value:
119 941 dimensionless
Details on results (HPLC method):
The three calibration series and three test item series were measured alternately. The adsorption coefficient Koc was determined based on a calibration curve using 7 reference items.
The capacity factors k’ were calculated from the dead time and retention times of the reference substances. The log k’ data of the reference substances were plotted against their log Koc values. The resulting calibration curve and the respective data are given in Figure 1 (attached) and Table 1 (below), respectively. The equation of the curve fitted to the calibration points is as follows:
log k' = 0.202 * log Koc - 0.231 (Rsq = 0.983)

The capacity factors k’ and log Koc for Kronitex TXP were calculated based on the calibration data obtained with the reference substances.
The estimated log Koc 5.08
The estimated Koc 119941
Adsorption and desorption constants:
Not applicable.
Recovery of test material:
Not applicable.
Concentration of test substance at end of adsorption equilibration period:
Not applicable.
Concentration of test substance at end of desorption equilibration period:
Not applicable.
Details on results (Batch equilibrium method):
Not applicable.
Statistics:
Not applicable.

Table 1:      Measured and calculated data of the reference substances and test item

Chemical name

log KOC

Retention time (min)

log k'

log Koc

Accuracy
log unit

Repeatability
DlogKOC, log unit

from OECD 121

Calculated

Calculated

Sodium nitrate

-

1.48

for determination of dead time

1.48

1.48

1.48

1.47

1.48

Mean

1.48

CV%

0.3

Acetanilide

1.25

3.07

0.032

1.30

0.04

0.01

3.06

0.029

1.29

3.06

0.029

1.29

3.06

0.029

1.29

3.07

0.032

1.30

3.06

0.029

1.29

Mean

3.06

0.030

1.29

CV%

0.2

-

-

Methyl-benzoate

1.80

3.47

0.129

1.78

0.02

0.01

3.46

0.127

1.77

3.47

0.129

1.78

3.47

0.129

1.78

3.46

0.127

1.77

3.47

0.129

1.78

Mean

3.47

0.129

1.78

CV%

0.1

-

-

Atrazine

1.81

3.27

0.083

1.56

0.25

0.01

3.27

0.083

1.56

3.27

0.083

1.56

3.27

0.083

1.56

3.28

0.086

1.57

3.27

0.083

1.56

Mean

3.27

0.084

1.56

CV%

0.1

-

-

Table 1:      Measured and calculated data of the reference substances and test item (continued)

Chemical name

log KOC

Retention time (min)

log k'

log Koc

Accuracy
log unit

Repeatability
DlogKOC, log unit

from OECD 121

Calculated

Calculated

Linuron

2.59

4.95

0.371

2.98

0.39

0.01

4.95

0.371

2.98

4.96

0.372

2.99

4.96

0.372

2.99

4.96

0.372

2.99

4.96

0.372

2.99

Mean

4.96

0.372

2.98

CV%

0.1

-

-

Naphthalene

2.75

4.53

0.315

2.70

0.04

0.01

4.53

0.315

2.70

4.54

0.316

2.71

4.54

0.316

2.71

4.54

0.316

2.71

4.54

0.316

2.71

Mean

4.54

0.316

2.71

CV%

0.1

-

-

a-Endosulfan

4.09

6.89

0.564

3.93

0.15

0.01

6.89

0.564

3.93

6.90

0.564

3.94

6.90

0.564

3.94

6.91

0.565

3.94

6.91

0.565

3.94

Mean

6.90

0.564

3.94

CV%

0.1

-

-

DDT

5.63

13.51

0.911

5.65

0.03

0.01

13.51

0.911

5.65

13.55

0.912

5.66

13.55

0.912

5.66

13.57

0.913

5.66

13.57

0.913

5.66

Mean

13.54

0.912

5.66

CV%

0.2

-

-

Kronitex TXP

-

10.65

0.793

5.07

-

0.02

10.69

0.795

5.08

10.71

0.796

5.08

10.71

0.796

5.08

10.67

0.794

5.07

10.75

0.797

5.09

Mean

10.70

0.795

5.08

CV%

0.3

-

-

Conclusions:
The estimated log Koc 5.08
The estimated Koc 119941
Executive summary:

In the course of this study the estimated adsorption coefficient (Koc) of Kronitex TXP was determined using high performance liquid chromatography.

The estimated log Koc 5.08

The estimated Koc 119941

The estimated Koc indicates a high potential to adsorb to soils and sediments. Such a high potential would indicate that a material would bind tightly to soils and sediments and thus, reduce overall exposure potential.

Description of key information

Potential for soil adsorption.

Key value for chemical safety assessment

Koc at 20 °C:
119 941

Additional information

A screening organic carbon-water partitioning coefficient (Koc) is available for the substance, using a HPLC Estimation method. This resulted on a log Koc value of 5.08 at 25 °C with Koc of 119941. As such, adsorption to soil is deemed to be high, based on this study assessment. Such a high potential indicates that the substance would bind tightly to soils and sediments and thus, reduce overall exposure potential to aqueous organisms

.

[LogKoc: 5.08]