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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
Study period:
The study was conducted between 23 October 2014 and 01 July 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline 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
Principles of method if other than guideline:
None
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
other: Not applicable
Specific details on test material used for the study:
None
Radiolabelling:
no
Test temperature:
30 ºC
Details on study design: HPLC method:
The test system utilized a high performance liquid chromatograph. A commercially available cyanopropyl reverse phase HPLC column containing lipophilic and polar moieties was used.


Performance of the Test
Preparation of sample solution
Test item (0.1017 g) was diluted to 100 mL with mobile phase. This solution was further diluted by a factor of 10 using mobile phase.

Preparation of dead time solution
The dead time was determined by measuring the retention time of formamide (purity*: 99.94 %, 604 mg/L solution in mobile phase).
* Value quoted by supplier.

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 Series
Detector type: Variable Wavelength Detector (VWD)
Column: Waters XSelect HSS CYANO 5µm (150 x 4.6 mm id)
Column temperature: 30 ºC
Mobile phase: Acetonitrile: purified water (55:45 v/v)
pH of mobile phase: 6.5
Flow-rate: 1.0 mL/min
Injection volume: 10 µL
VWD wavelength: dead time and reference standards: 210 nm
sample: 590 nm

Calculation
Construction of calibration curve
A calibration curve was constructed from the retention time data of the dead time and reference standard solutions. The capacity factors (k') for the reference standards were calculated using the equation below

Adsorption coefficient of sample
The capacity factor was calculated using the equation below and the log10 Koc value determined using the equation below with reference to the calibration curve.


Capacity factor
The capacity factor was determined using the equation below:

k’ = (tr – t0) / t0

where:
k' = capacity factor
tr = retention time (min)
t0 = dead time (min)

A correlation of log k' versus log Koc of the calibration standards was plotted using linear regression.

Capacity factor
The capacity factor was determined using the equation below:

k’ = (tr – t0) / t0

where:
k' = capacity factor
tr = retention time (min)
t0 = dead time (min)

A correlation of log k' versus log Koc of the calibration standards was plotted using linear regression.


Adsorption Coefficient
The adsorption coefficient was calculated using the equation below:

Log10 Koc = (Log10 k’ – A) / B

where:
Koc = adsorption coefficient
k' = capacity factor
A = intercept of the calibration curve
B = slope of the calibration curve

The mobility classification of the test item was obtained by comparing the calculated Koc value to the mobility classes according to P.J. McCall, R.L. Swann, D.A. Laskowski, S.M. Unger, S.A. Vrona and H.J. Dishburger “Estimation of Chemical Mobility in Soil from Liquid Chromatography Retention Times”; Bull. Environm. Contam. Toxicol. 24, 190-195 (1980).
Analytical monitoring:
no
Sample No.:
#1
Type:
Koc
Value:
< 17.8
Temp.:
30 °C
Key result
Sample No.:
#1
Type:
log Koc
Value:
< 1.25
Temp.:
30 °C
Details on results (HPLC method):
The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8 with log10 Koc less than 1.25.

Calibration

The retention times of the dead time and the retention times, capacity factors (k') and log10 Kocvalues 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

1.827

1.788

1.808

 

Standard

Retention Time (mins)

Mean Retention Time (mins)

Capacity Factor (k')

Log10k'

Log10Koc

Injection 1

Injection 2

Acetanilide

2.357

2.342

2.349

0.300

-0.523

1.25

Phenol

2.449

2.405

2.427

0.343

-0.465

1.32

Atrazine

2.906

2.906

2.906

0.608

-0.216

1.81

Isoproturon

2.993

3.183

3.088

0.708

-0.150

1.86

Triadimenol

3.290

3.236

3.263

0.805

-0.094

2.40

Linuron

3.542

3.518

3.530

0.953

-0.021

2.59

Naphthalene

3.761

3.771

3.766

1.083

0.035

2.75

Endosulfan-Diol

3.562

3.562

3.562

0.970

-0.013

3.02

Fenthion

4.694

4.694

4.694

1.597

0.203

3.31

a-Endosulfan

5.845

5.836

5.841

2.231

0.349

4.09

Diclofop-Methyl

5.666

5.661

5.663

2.133

0.329

4.20

Phenanthrene

4.801

4.801

4.801

1.656

0.219

4.09

DDT

8.367

8.377

8.372

3.632

0.560

5.63

Adsorption coefficient of sample

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

Injection

Retention Time (mins)

Capacity Factor (k')

Log10k'

Log10Koc

Mean Log10Koc

Adsorption Coefficient

1

1.137

< 0.300

< -0.523

< 1.25

< 1.25

< 17.8

2

1.137

< 0.300

< -0.523

< 1.25

 

Validity criteria fulfilled:
yes
Conclusions:
The adsorption coefficient (Koc) of the test item has been determined to be less than 17.8, log10 Koc less than 1.25. These values indicate that the test item will have a very high mobility.
Executive summary:

The adsorption coefficient of the test substance was determined in a study conducted according to OECD Guideline 201 and EU Method C.19. The high performance liquid chromatography (HPLC) method was used for this purpose. Based on the findings of the study, the adsorption coefficient (Koc) of the test item has been determined to be less than 17.8, log10 Koc less than 1.25. These values indicate that the test item will have a very high mobility.

Description of key information

The adsorption coefficient of the test substance was determined to be less than 17.8, and log Koc less than 1.25. These values indicate that the test item will have a very high mobility.

Key value for chemical safety assessment

Koc at 20 °C:
17.8

Additional information

The adsorption coefficient of the test substance was determined in a study conducted according to OECD Guideline 201 and EU Method C.19. The high performance liquid chromatography (HPLC) method was used for this purpose. Based on the findings of the study, the adsorption coefficient (Koc) of the test item has been determined to be less than 17.8, log10 Koc less than 1.25. These values indicate that the test item will have a very high mobility.

[LogKoc: 1.25]