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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
no
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:
yes (incl. QA statement)
Type of method:
HPLC estimation method
Details on study design: HPLC method:
Performance of the Test
Preparation of dead time solution
The dead time was determined by measuring the retention time of formamide (purity* 99.6%) at 646 mg/L solution in methanol.
Preparation of reference standard solutions
Solutions of reference standards (see following table) were prepared in methanol.
Standard Purity (%)* Concentration (mg/L)
Acetanilide 99+ 103
Atrazine 99.1 103
Triadimenol 98.0 100
Linuron 99.7 101
Naphthalene 99.0 110
Endosulfan-diol 99.9 104
Fenthion 97.5 112
Endosulfan 99.6 107
Phenanthrene ≥99.5 107
Diclofop-methyl 99.1 115
DDT 98.7 104


Preparation of sample solution
Test item (0.1997g) was diluted to 20 mL with tetrahydrofuran and further diluted by a factor of 10 to give a concentration of 0.999 g/L.

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 1200, incorporating workstation and autosampler
Detectors : Agilent variable wavelength detector (VWD)
evaporative light scattering (ELS)
Column : Waters XSelect HSS CN 5µm (150 x 4.6 mm id)
Column temperature : 30 °C
Mobile phase : methanol:water (55:45 v/v)
pH of mobile phase : 3.0, adjusted with trifluoroacetic acid
Flow-rate : 1.0 mL/min
Injection volume : 5 µL
VWD wavelength : 210 nm (dead time and reference standards)
ELSD parameters : nebuliser temperature: 40 °C
evaporator temperature: 80 °C
gas flow: 1.0 L/min

The mobile phase was ramped to 100% tetrahydrofuran shortly after the elution of the last reference standard in order to elute any highly retained test item components. This was carried out for the sample and sample blank injections only.

Key result
Type:
log Koc
Value:
>= 5.04 dimensionless
pH:
3
Remarks on result:
other: the adsorption coefficient of the test substance was determined to be in the range 1.10 x 10E5 to >4.27 x 10E5, log10 Koc of 5.04 to > 5.63

Results

The retention times of the dead time and the retention times, capacity factors (k') and log10 Koc values for the reference standards are shown in the following table:

Table 8

Standard

Retention Time (min)

Mean Retention Time (min)

Capacity Factor (k')

Log10k'

Log10Koc

Injection 1

Injection 2

Formamide (dead time)

1.914

1.910

1.912

-

-

-

Acetanilide

2.629

2.629

2.629

0.375

-0.426

1.25

Atrazine

3.620

3.615

3.618

0.892

-4.96 x 10-2

1.81

Triadimenol

5.214

5.214

5.214

1.727

0.237

2.40

Linuron

5.369

5.369

5.369

1.808

0.257

2.59

Naphthalene

4.636

4.636

4.636

1.424

0.154

2.75

Endosulfan-diol

6.710

6.710

6.710

2.510

0.400

3.02

Fenthion

7.935

7.940

7.937

3.151

0.498

3.31

a-Endosulfan

11.341

11.346

11.344

4.933

0.693

4.09

Diclofop-methyl

12.187

12.191

12.189

5.375

0.730

4.20

Phenanthrene

8.683

8.683

8.683

3.541

0.549

4.09

DDT

24.057

24.062

24.06

11.583

1.06

5.63

The calibration curve from which the sample results were taken from is shown as Figure 3 - attached to this Summary.

Adsorption Coefficient

The retention times, capacity factor and log10Kocvalue determined for the sample are shown in the following table:

Table 9

Peak

Injection

Retention Time (min)

Capacity Factor (k')

Log10k'

Log10Koc

Mean
Log10Koc

1

1

19.252

9.07

0.958

5.04

5.04

2

19.341

9.12

0.960

5.04

2

1

24.477

>11.6

>1.06

>5.63

>5.63

2

24.539

>11.6

>1.06

>5.63

3 to 6

1

≥34.100

>11.6

>1.06

>5.63

>5.63

2

≥34.106

>11.6

>1.06

>5.63

Overall log10Koc: 5.04 to > 5.63
Overall adsorption coefficient: 1.10 x 105 to >4.27 x 105

Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the adsorption coefficient of the test substance has been determined to be in the range of 1.10+E5 to >4.27+E5, log10 Koc of 5.04 to >5.63. This result classifies the test substance as immobile.
Executive summary:

A study was conducted to determine adsorption/desorption coefficient of the test substance. The determination was carried out using the HPLC screening method, designed to be compatible with OECD Guideline 121 and EU Method C.19. The test system utilized a high performance liquid chromatograph (HPLC). A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used. Under the study conditions, the adsorption coefficient of the test substance wasdetermined to be in the range of 1.10+E5 to >4.27+E5, log10 Koc of 5.04 to > 5.63. This result classifies the test substance as immobile (Envigo, 2018).

Description of key information

Key value for chemical safety assessment

Koc at 20 °C:
5.04

Additional information

A study was conducted to determine adsorption/desorption coefficient of the test substance. The determination was carried out using the HPLC screening method, designed to be compatible with OECD Guideline 121 and EU Method C.19. The test system utilized a high performance liquid chromatograph (HPLC). A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used. Under the study conditions, the adsorption coefficient of the test substance was determined to be in the range of 1.10+E5 to >4.27+E5, log10 Koc of 5.04 to > 5.63. This result classifies the test substance as immobile (Envigo, 2018).

[LogKoc: 0.702]

[LogKoc: 0.702]