α-(2,4-dichlorophenyl)-1H-imidazole-1-ethanol

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-04-23 to 2008-06-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.1220 (Sediment and Soil Adsorption / Desorption Isotherm)

Qualifier:

equivalent or similar to guideline

Guideline:

other: Commission Directive 95/36/EC; July 14, 1995; amending Council Directive 91/414/EEC concerning plant protection products. Annex II, Part A: Chemical Substances, Section 7.1.2; Adsorption and Desorption, 1991.

Qualifier:

equivalent or similar to guideline

Guideline:

other: SETAC (Europe): Procedures for assessing the enviornmental fate and ecotoxicity of pesticides Part 1, Section 4, March 1995.

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 00512242
- Expiration date of the lot/batch: 27 June 2013
- Purity: 100.3%

Radiolabelling:

no

Test temperature:

All experiments were performed at a constant temperature of 20 ± 2°C.

Analytical monitoring:

yes

Details on sampling:

Samples of supernatant were taken after 48 hours.

Matrix no.:

#1

Matrix type:

loam

% Org. carbon:

3.79

pH:

7.08

CEC:

14.34 other: mmol/100 g soil

Matrix no.:

#2

Matrix type:

silt loam

% Org. carbon:

4.482

pH:

6.7

CEC:

14.2 other: mmol/100 g soil

Matrix no.:

#3

Matrix type:

sandy loam

% Org. carbon:

0.89

pH:

7.58

CEC:

7.77 other: mmol/100 g soil

Details on matrix:

COLLECTION AND STORAGE
Soil 1 (Gartenacker) was sampled within 2 cm and max. 20 cm ground depth from a field in Vouvry (Valais , Switzerland; latitude 46° 20' N, longitude 6° 53' E) in February 2008.
Soil 2 (Fislis) was sampled from the top 20 cm layer from an agricultural area in Fislis (Alsace, France; latitude 47° 30' N, longitude 7° 21' E) in April 2007.
Soil 3 (Pappelacker) was sampled from the top 20 cm layer from an agricultural area in Vouvry (Valais , Switzerland; latitude 46° 20' N, longitude 6° 53' E) in January 2008.
None of the soils had been fertilized or treated with pesticides for at least 12 months prior to sampling. All soils were sieved to 2 mm by RCC Ltd before use.

Details on test conditions:

- Soil:solution ratios = 1:1 m/v (10 g soil and 9 mL solution), 1:5 m/v (5 g soil and 22.5 mL solution),1:25 m/v (1 g soil and 22.5 mL solution)
- Spiking rates: 2.01, 0.5, 0.1, 0.05 and 0.02 mg/L

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Kads, Foc

Value:

1 383 L/kg

pH:

7.08

Matrix:

Soil I

% Org. carbon:

2.2

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Kdes,Foc

Value:

1 850 L/kg

pH:

7.08

Matrix:

Soil I

% Org. carbon:

2.2

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Kads,Foc

Value:

757 L/kg

pH:

6.7

Matrix:

Soil II

% Org. carbon:

2.6

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Kdes,Foc

Value:

916 L/kg

pH:

6.7

Matrix:

Soil II

% Org. carbon:

2.6

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Kads,Foc

Value:

1 663 L/kg

pH:

7.58

Matrix:

Soil III

% Org. carbon:

0.89

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Kdes,Foc

Value:

1 907 L/kg

pH:

7.58

Matrix:

Soil III

% Org. carbon:

0.89

Validity criteria fulfilled:

yes

Conclusions:

In this study, adsorption of the test substance was determined on 3 soils using the Batch equilibrium method. The calculated Kads,Foc values indicated a high sorption onto soil. The calculated Kdes,Foc values were in the same range indicating a reversible adsorption process and a high sorption to soil. The average of the available 3 Kads,Foc values with a soil/solution ratio of 1/25 was 1267 L/kg. The average of the available 3 Kdes,Foc values with a soil/solution ratio of 1/25 was 1558 L/kg.

Reference 2

Endpoint:

adsorption / desorption, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

7 May to 25 June 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Common name: R014821
- Source and lot/batch No.of test material: PROF_0001_202_2
- Expiration date of the lot/batch: 31 January 2013
- Purity test date: 7 February 2009
- Purity: 99.4%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: room temperature

Radiolabelling:

no

Test temperature:

All experiments were done at laboratory ambient temperature (between 20 and 25°C)

Analytical monitoring:

yes

Details on sampling:

- Concentrations:
*Tier 1 and 1: application solution was 0.32 mg/L
- 3 soil/solution ratios were used (6 experiments):
*50 g soil and 50cm3 aqueous solution of the test substance (ratio 1/1)
*10 g soil and 50cm3 aqueous solution of the test substance (ratio 1/5)
*2 g soil and 50cm3 aqueous solution of the test substance (ratio 1/25)
All experiments, including controls and blanks were performed in duplicates.

- Sampling interval: The sampling times were 48 hrs after application (adsorption) and 2, 5, 24, 48 hours after replacing the 0.01 M CaCl2 solution (desorption)
- Sample storage before analysis: Samples were stored at room temperature in the dark


*Tier 3: Adsorption isotherms estimated at five concentrations: 0.1875, 0.0944, 0.0241, 0.0053 and 0.0019 mg/L.
*Tier 3: Desorption study was performed at a concentration of 0.25 mg/L

Matrix no.:

#1

Matrix type:

sand

% Org. carbon:

0.64

pH:

5.31

CEC:

3.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.454

Details on matrix:

COLLECTION AND STORAGE
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): soil was air dried at ambient temperature (between 20-25 °C). The soils were already delivered sieved to a particle size <= 2. Moisture content of the soil was determined by heating 3 aliquots at 105°C until there was no significant change in weight (approx. 12 hrs).

Determination of the physical-chemical parameters of the soil was done by LUFA Speyer.

PROPERTIES
- Soil series: 1 soil (LUFA 2.1) was used.
- pH: 5.31
- Organic carbon (%): 0.64
- CEC (meq/100 g): 3.6
- Moisture at 1/3 atm (%): 32.4
- Bulk density (g/cm3): 1.454

Details on test conditions:

Air-dry soil samples were equilibrated by shaking with a maximum of 90% of the final volume of 0.01 M CaCl2 overnight (at least 12 hours) before application. The application solution of the test item was added and the final volume was adjusted to 50 cm3. The test was performed by the serial method in 200 mL glass centrifuge tubs with PTEE sealed scew caps. Agitation was performed on a flat bed shaker with a fequency of around 130 rpm to hold the soil dispersed in the aquous volume. At pre-determined sampling times the samples were centrifuged for 10 min with 2900 rpm and aliquots of 100-500 µL were taken form the supernatant of each centrifuge tube and mixed with 100-500 µL acetonitrile during the adsorption study.

Computational methods:

The percentage adsorption A (ti) was calculated at each time point (ti) on the basis of the nominal initial concentration and the measured concentration in the supernatant at the sampling time (ti). Plots of A (ti) versus time were generated in order to estimate the achievement of equilibrium plateau. The Kd value at equilibrium as well as carbon normalized adsorption coefficient Koc (for non-polar organic chemicals), was also calculated. All the applicable equations and principles of plotting are given in the Data and Reporting section.

Sample No.:

#1

Type:

Koc

Value:

6 406.3 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/25 soil/solution ratio

Sample No.:

#1

Type:

log Koc

Value:

3.81 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/25 soil/solution ratio

Sample No.:

#1

Type:

Kd

Value:

41 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/25 soil/solution ratio

Sample No.:

#2

Type:

Koc

Value:

4 843.8 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/5 soil/solution ratio

Sample No.:

#2

Type:

log Koc

Value:

3.69 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/5 soil/solution ratio

Key result

Sample No.:

#2

Type:

Kd

Value:

31 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/5 soil/solution ratio

Sample No.:

#3

Type:

Koc

Value:

7 218.8 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/1 soil/solution ratio

Sample No.:

#3

Type:

log Koc

Value:

3.86 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/1 soil/solution ratio

Key result

Sample No.:

#3

Type:

Kd

Value:

46.2 L/kg

% Org. carbon:

0.64

Remarks on result:

other: 1/1 soil/solution ratio

Adsorption and desorption constants:

- Adsorption coefficients (48 hrs) (Tier 1 and 2):
results: see results and discussion section

- Adsorption isotherm results (48 hrs) (Tier 3):
Slope (1/n): 0.7666
Intercept: 0.8894
Freundlich adsorption coefficient: 7.2344
R Squared: 0.9864
% oc: 0.64

- Desorption coefficients (Tier 1 and 2):
D (%): 58.5
Kd: 17.6
Koc: 2750
log Koc: 3.44
% o.c: 0.64

- Desorption isotherm results (48 hrs) (Tier 3):
Slope (1/n): 0.6667
Intercept: 0.8220
Freundlich desorption coefficient: 6.6374
R Squared: 0.9412
% oc: 0.64

Recovery of test material:

Recovery control: sample 1: 103.1%; sample 2: 101.9%
Recovery test material (1/25): sample 1: 90%; sample 2: 96.3%

Concentration of test substance at end of adsorption equilibration period:

Tier 1 and 2 Adsorption:
- soil: LUFA 2.1
- sample concentration: 16 µg test item
- adsorption equilibrium: reached after 24 hrs for all soil/solution ratios
- adsorption: 97.7% at soil solution ratio of 1/1

Tier 3 Adsorption:
- soil solution ratio: 1/25
- experimental procedure: identical to Tier 1and 2
- concentration range: 0.00199 - 0.1875 mg/L in 50 mL CaCl2
- mass balance: indicated that the test item was stable during the time scale of the experiment. Amount of test item bound to the tuve wall was negligible.
- Concentration of R014821 in water phase at adsorption equilibrium after 48 hrs:
*at conc. of 0019 mg/L: 0.0008 mg/L
*at conc. of 0.0053 mg/L: 0.0024 mg/L
*at conc. of 0.0241 mg/L: 0.0138 mg/L
*at conc. of 0.0944 mg/L: 0.0629 mg/L
*at conc. of 0.1875 mg/L: 0.1225 mg/L

- Concentration of R014821 bound to soil:
*at conc. of 0019 mg/L: 0.0283 mg/L
*at conc. of 0.0053 mg/L: 0.0732 mg/L
*at conc. of 0.0241 mg/L: 0.2588 mg/L
*at conc. of 0.0944 mg/L: 0.7888 mg/L
*at conc. of 0.1875 mg/L: 1.6250 mg/L

Concentration of test substance at end of desorption equilibration period:

Tier 1 and 2 Desorption:
- soil: LUFA 2.1
- sample concentration: 12.6 µg test item
- adsorption equilibrium: reached after 24 hrs for all soil/solution ratios
- adsorption: 48.8%

Tier 3 Desorption:
- soil solution ratio: 1/25
- experimental procedure: identical to Tier 1and 2
- concentration range: 0.0012 - 0.0675 mg/L in 50 mL CaCl2
- mass balance: indicated that the test item was stable during the time scale of the experiment. Amount of test item bound to the tuve wall was negligible.
- Concentration of R014821 in water phase at desorption equilibrium bound to soil:
*at conc. of 0012 mg/L: - mg/L
*at conc. of 0.0030 mg/L: 0.0007 mg/L
*at conc. of 0.0107 mg/L: 0.0043 mg/L
*at conc. of 0.0329 mg/L: 0.0182 mg/L
*at conc. of 0.0675 mg/L: 0.0326 mg/L

- Concentration of R014821:
*at conc. of 0012 mg/L: 0.0295 mg/L
*at conc. of 0.0030 mg/L: 0.0569 mg/L
*at conc. of 0.0107 mg/L: 0.1588 mg/L
*at conc. of 0.0329 mg/L: 0.3688 mg/L
*at conc. of 0.0675 mg/L: 0.8765 mg/L

Sample no.:

#1

Duration:

48 h

% Adsorption:

97.9

Remarks on result:

other: LUFA 2.1 (ratio 1/1)

Sample no.:

#2

Duration:

48 h

% Adsorption:

86.2

Remarks on result:

other: LUFA 2.1 (ratio 1/5)

Sample no.:

#3

Duration:

48 h

% Adsorption:

62.3

Remarks on result:

other: LUFA 2.1 (ratio 1/25)

Sample no.:

#4

Duration:

48 h

% Adsorption:

0.7

Remarks on result:

other: control

Sample no.:

#1

Duration:

48 h

% Desorption:

58.8

Remarks on result:

other: LUFA 2.1 (ratio 1/25)

Validity criteria fulfilled:

yes

Conclusions:

In this study, adsorption of the test substance on 1 sandy soil using the HPLC method The log Koc values were reported to be 3.81, 3.69 and 3.86 L/kg for 1/25, 1/5 and 1/1 soil/solution ratios, respectively. The Kd values were 41, 31 and 46.2 L/kg for 1/25, 1/5 and 1/1 soil/solution ratios, respectively. Control samples revealed that no test item adhered to the test vessel and the test item was stable during the 48 hours incubation period. The mass balance was performed after the end of the Tier 1 and 2 testing for the soil/solution ratio of 1/25. For this ratio the recovery was > 90%, therefore the test item was considered tobe stable during the test. The amount of desorption was < 75% of the amount adsorbed, so the adsorption was considered to be non-reversible.

Description of key information

In total, two studies were selected as useful for covering the adsorption/desorption endpoint using a weight of evidence approach.

In the study of Flörchinger (2009), adsorption of the test substance was determined on 1 sandy soil using the HPLC method.  The log Koc values were reported to be 3.81, 3.69 and 3.86 L/kg for 1/25, 1/5 and 1/1 soil/solution ratios, respectively. The Kd values were 41, 31 and 46.2 L/kg for 1/25, 1/5 and 1/1 soil/solution ratios, respectively.

In the study from Adam (2008), three soils were used at a soil/solution ratio of 1/25. The calculated Kads,Foc values indicated a high sorption onto soil. The calculated Kdes,Foc values are in the same range indicating a reversible adsorption process and a high sorption to soil. The average of the available 3 Kads,Foc values with a soil/solution ratio of 1/25 was 1267 L/kg. The average of the available 3 Kdes,Foc values with a soil/solution ratio of 1/25 was 1558 L/kg.

Taking the average of the log Koc value of the first study (Flörchinger, 2009) at soil/solution ratio of 1/25 (3.81) , and Kads,Foc for soil/solution ratio of 1/25 of the second study (Adam, 2008) (Koc of 1267 L/kg), the following final key value was retained: i.e. a log Koc of 3.46 L/kg.

Key value for chemical safety assessment

Koc at 20 °C:

2 860