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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:
Testing was conducted between 15 June 2011 and 20 December 2011.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions.
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 determination was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22
Deviations:
no
Qualifier:
equivalent or similar 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:
The determination was carried out using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of method:
other: HPLC Screening Method
Media:
other: test item and reference standards prepared in methanol
Radiolabelling:
no
Test temperature:
30ºC (column temperature in HPLC)
Details on study design: HPLC method:
Procedure:
Preparation of sample solution:
Test item (0.2316 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 99.99%, 756 mg/l solution in mobile phase)
.
Preparation of reference standard solutions:
Solutions of reference standards (see following table) were prepared in methanol.


Standard Purity (%) Concentration (mg/l)
Acetanilide 99+ 116
Phenol 99+ 113
Atrazine 97.2 103
Isoproturon 99.9 114
Triadimenol 98.4 119
Linuron 99.7 113
Naphthalene 99+ 105
Endosulfan-diol 99.9 150
Fenthion 98.3 126
α-Endosulfan 99.6 133
Phenanthrene 97 120
Diclofop-methyl 99.2 129
DDT 98 160

Determination of retention time:
The sample, dead time and reference standard solutions were injected in duplicate using the following HPLC parameters:
HPLC System : Agilent Technologies 1100, incorporating autosampler and workstation
Column : Luna CN 5 µm (150 x 4.6 mm id)
Column temperature: 30ºC
Mobile phase : methanol:water (55:45 v/v) adjusted to pH 7.2 with 0.1M sodium hydroxide
pH of mobile phase: 7.2
Flow-rate : 1.0 ml/min
Injection volume: 25 µl
UV detector wavelength : 210 nm


Construction of calibration curve:
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions (Figure 12.1 - see attached background material). The capacity factors (k) for the reference standards were calculated using Equation 12.1 (see any other information on methods and materials section).


Adsorption coefficient of sample
The capacity factor was calculated using Equation 12.1 and the log10 Koc value determined using Equation 12.2 (see any other information on methods and materials section) with reference to the calibration curve (Figure 12.1 - attached background material).

Please see attached background material for Typical Chromatography.














Key result
Type:
Koc
Value:
< 17.8 L/kg
Temp.:
30 °C
Key result
Type:
log Koc
Value:
< 1.25 dimensionless
Temp.:
30 °C
Details on results (HPLC method):
See any other information on results incl. tables section.
Transformation products:
not measured
Details on results (Batch equilibrium method):
In this case Not applicable.

Calibration

The retention times of formamide and the retention times, capacity factors (k) and log10Kocvalues for the reference standards are shown in the two following tables:

Dead Time

Retention Time (mins)

Mean Retention Time (mins)

Injection 1

Injection 2

Formamide

2.037

2.037

2.037

Standard

Retention Time (mins)

Mean Retention Time (mins)

Capacity Factor (k)

Log10k

Log10Koc

Injection 1

Injection 2

Acetanilide

2.409

2.408

2.408

0.183

-0.739

1.25

Phenol

2.368

2.368

2.368

0.163

-0.789

1.32

Atrazine

2.636

2.635

2.635

0.294

-0.532

1.81

Isoproturon

2.824

2.825

2.824

0.387

-0.412

1.86

Triadimenol

2.971

2.971

2.971

0.459

-0.339

2.40

Linuron

3.242

3.242

3.242

0.592

-0.228

2.59

Naphthalene

3.923

3.923

3.923

0.926

-3.332 x 10-2

2.75

Endosulfan-diol

3.239

3.239

3.239

0.59

-0.229

3.02

Fenthion

4.535

4.535

4.535

1.227

8.881 x 10-2

3.31

a-Endosulfan

5.287

5.287

5.287

1.596

0.203

4.09

Phenanthrene

5.974

5.97

5.972

1.932

0.286

4.09

Diclofop-methyl

5.516

5.518

5.517

1.709

0.233

4.20

DDT

12.27

12.263

12.266

5.023

0.701

5.63

 

Adsorption coefficient of sample

The retention times, capacity factors and log10Kocvalues determined for the sample are shown in the following table:

Injection

Retention Time (mins)

Capacity Factor (k)

Log10k

Log10Koc

1

1.437

-0.291

<-0.739

<1.25

2

1.452

-0.291

<-0.739

<1.25

Log10Koc:                            <1.25
Adsorption coefficient:        <17.8


Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 (log10 Koc <1.25).
Executive summary:

The adsorption coefficient determination was carried outusing the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

The method guideline states that the measurement of adsorption coefficient should be carried out on substances in their ionised and unionised forms. However, the dissociation constants of the functional groups found in the test item made it impossible to satisfy this criterion. The test item contained both basic and acidic functional groups. The acidic functional groups also contained strong acids, such that a pH of at least 0 would be required to obtain an unionised form. However acidification of the mobile phase, even to address the weaker acidic groups, would promote ionisation of the amine group to give a zwitterion. In addition, such a mobile phase pH is both significantly outside the environmentally relevant pH range for this test and also experimentally impractical. Therefore testing was carried out at an approximately neutral pH, with the acidic functional groups either ionised or partially ionised and the amine functional group also partially ionised.

The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 (log Koc <1.25).

Description of key information

In a single key study conducted in accordance with OECD 107 (HPLC SCREENING), THE adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 L/kg (log Koc = <1.25).

Key value for chemical safety assessment

Koc at 20 °C:
17.8

Additional information

The adsorption coefficient was determined to be < 17.8 L/kg (log Koc <1.25) using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

The method guideline states that the measurement of adsorption coefficient should be carried out on substances in their ionised and unionised forms. However, the dissociation constants of the functional groups found in the test item made it impossible to satisfy this criterion. The test item contained both basic and acidic functional groups. The acidic functional groups also contained strong acids, such that a pH of at least 0 would be required to obtain an unionised form. However acidification of the mobile phase, even to address the weaker acidic groups, would promote ionisation of the amine group to give a zwitterion. In addition, such a mobile phase pH is both significantly outside the environmentally relevant pH range for this test and also experimentally impractical. Therefore testing was carried out at an approximately neutral pH, with the acidic functional groups either ionised or partially ionised and the amine functional group also partially ionised.

[LogKoc: 1.25]

[LogKoc: 1.25]