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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study conducted to GLP and in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not effect the quality of the relevant results.
Qualifier:
equivalent or similar 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:
The preocedure used was that specified in the OECD Draft document (December 1998): Estimation of the adsorption coefficient (Koc) on soil and sewage sludge using high performance lliquid chromatography.
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
HPLC estimation method
Radiolabelling:
no
Test temperature:
HPLC Column temperature: 30ºC
Details on study design: HPLC method:
Performance of the Test:
Preparation of sample solution:
Test item (0.0212 g) was diluted to 100 mL with mobile phase.

Preparation of dead time solution:
The dead time was determined by measuring the retention time of formamide (purity 99.5%) at 695 mg/L solution in methanol.

Preparation of reference standard solutions:
Solutions of reference standards (see table 9.1 within the any other information on materials and methods incl. tables section below) were prepared in methanol.

Determination of retention time:
The sample, formamide and reference standard solutions were injected in duplicate using the following HPLC parameters:

HPLC System: Hewlett Packard 1050, incorporating autosampler and workstation
Column: Luna 5 µ CN (250 x 4.6 mm id)
Column temperature: 30ºC
Mobile phase: Methanol:water (55:45 v/v)
pH of mobile phase: 8.1 adjusted with 1 M sodium hydroxide
Flow-rate: 1.0 mL/min
UV detector wavelength : 210 nm
Injection volume: 10 µL



Type:
log Koc
Value:
3.23 dimensionless
Temp.:
30 °C
Type:
Koc
Value:
1 690 L/kg
Temp.:
30 °C
Transformation products:
not measured

Calibration

The retention times of formamide and the reference standards are shown in the tables below

Dead Time

Retention Time (mins)

Mean Retention Time (mins)

Injection 1

Injection 2

Formamide

3.169

3.174

3.172

Reference standards

Standard

Retention Time (mins)

Mean Retention Time (mins)

Capacity Factor (k)

Log10 k

Log10 Koc

Injection 1

Injection 2

Acetanilide

3.922

3.919

3.921

0.236

-0.627

1.25

Phenol

3.948

3.951

3.950

0.245

-0.610

1.32

Atrazine

4.290

4.297

4.294

0.354

-0.451

1.81

Aniline

4.019

4.018

4.019

0.267

-0.573

2.07

Triadimenol

5.351

5.346

5.349

0.686

-0.163

2.40

Linuron

5.824

5.824

5.824

0.836

-7.761x10 -2

2.59

Naphthalene

6.507

6.518

6.513

1.053

2.261x10 -2

2.75

 

Fenthion

8.409

8.421

8.415

1.653

0.218

3.31

Alpha endosulfan

9.214

9.196

9.205

1.902

0.279

4.09

 

Phenanthrene

9.536

9.525

9.531

2.005

0.302

4.09

 

Diclofop-methyl

9.291

9.274

9.283

1.927

0.285

4.20

DDT

17.275

17.259

17.267

4.444

0.648

5.63

Adsorption coefficient of sample

The retention times, capacity factors and log10 Koc values determined are shown in the table below

Injection

Retention Time (mins)

Capacity Factor (k)

Log10k

Log10Koc

1

6.487

1..045

1.928 x 10 -2

3.224

2

6.502

1.050

2.124 x 10 -2

3.230

Mean Log10 Koc : 3.23

Adsorption coefficient : 1690

Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient (Koc) of the test item has been determined to be 1690 (log Koc = 3.23).
Executive summary:

Method

The determination was carried out using the HPLC screening method. The procedure used was that specified in the OECD draft document (December 1998): Estimation of the Adsorption Coefficient (Koc) on soil and sewage sludge using High Performance liquid chromatography.

Discussion

The pH of the mobile phase was adjusted to 8.1 to ensure the test material was analysed in its non-ionised form.

The test material has 3 pKa's one of which was estimated to be 6.1.In this circumstance the test guideline states that the adsorption coefficient should be measured on the ionised and non ionised forms. Accordingly HPLC analysis was also carried out with the eluent pH adjusted to 4.2; under these conditions eluting test material was not detected (using UV and refractive index detection). It is likley that the ionised functional group caused the test material to interact with the cyanopropyl column in a manner other than the partitioning between stationary and mobile phases. Consequently, the adsorption coefficient could only be estimated for the non ionised form of the test material, however, this is the form that would be predominant under environmentally relevent conditions.

Conclusion

The adsorption coefficient (Koc) of the test item has been determined to be 1690 L/kg (log Koc = 3.23).

Description of key information

The adsorption coefficient (Koc) of the test item has been determined to be 1690 (log Koc 3.23).

Key value for chemical safety assessment

Koc at 20 °C:
1 690

Additional information

Method

The determination was carried out using the HPLC screening method. The procedure used was that specified in the OECD draft document (December 1998): Estimation of the Adsorption Coefficient (Koc) on soil and sewage sludge using High Performance liquid chromatography.

Discussion

The pH of the mobile phase was adjusted to 8.1 to ensure the test material was analysed in its non-ionised form.

The test material has 3 pKa's one of which was estimated to be 6.1.In this circumstance the test guideline states that the adsorption coefficient should be measured on the ionised and non ionised forms. Accordingly HPLC analysis was also carried out with the eluent pH adjusted to 4.2; under these conditions eluting test material was not detected (using UV and refractive index detection). It is likley that the ionised functional group caused the test material to interact with the cyanopropyl column in a manner other than the partitioning between stationary and mobile phases. Consequently, the adsorption coefficient could only be estimated for the non ionised form of the test material, however, this is the form that would be predominant under environmentally relevent conditions.

Conclusion

The adsorption coefficient (Koc) of the test item has been determined to be 1690 L/kg (log Koc 3.23).