N-[2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)-phenyl-aminocarbonyl]-2,6-difluorobenzamide

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Remarks:

batch equilibrium method

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 Sep 1991 to 11 Mar 1992

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)

Version / remarks:

May 12, 1981

Qualifier:

according to guideline

Guideline:

other: EPA 163-1

Version / remarks:

October 18, 1982

Qualifier:

according to guideline

Guideline:

other: Environmental Chemistry and Fate, Guidelines for Registration of Pesticides in Canada

Version / remarks:

Section B: Mobility, 1: Adsorption-Desorption Merasurements,July 15,1987

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1 °C

Analytical monitoring:

yes

Matrix no.:

#1

Matrix type:

loamy sand

% Clay:

4.2

% Silt:

17.1

% Sand:

78.7

% Org. carbon:

0.77

pH:

7

CEC:

6.35 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

sand

% Clay:

2.5

% Silt:

1

% Sand:

96.5

% Org. carbon:

0.43

pH:

5.7

CEC:

3.41 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

silt loam

% Clay:

15.2

% Silt:

42.3

% Sand:

42.5

% Org. carbon:

1.39

pH:

5.7

CEC:

12.7 meq/100 g soil d.w.

Matrix no.:

#4

Matrix type:

silt loam

% Clay:

24.8

% Silt:

56.8

% Sand:

18.4

% Org. carbon:

4.39

pH:

7.1

CEC:

30.7 meq/100 g soil d.w.

Matrix no.:

#5

Matrix type:

other: Humic soil

% Clay:

23.6

% Silt:

55.4

% Sand:

21

% Org. carbon:

19.4

pH:

6.6

CEC:

113.7 meq/100 g soil d.w.

Details on matrix:

An overview of the soil origin and propoerties is provided in Table 1 in 'Any other information on materials and methods incl. tables'
- Soil Preparation: The soils were air-dried at room temperature and passed through a 1 mm sieve.

Details on test conditions:

An overview of the treatments is provided in Table 2 in 'Any other information on materials and methods incl. tables'
TEST SYSTEM
- Test vessel: 150 mL centrifuge tubes
- Amount of soil: 1 g for all soils (dry weight basis)
- Aqueous Phase: 100 mL of 0.01 mol CaCl2 solution
- Equilibration Time: The samples were shaken for 2 hours.
- Number of reaction vessels/concentration: The highest concentration was performed in duplicate. The rest concentrations were 1 replicate.
- Method of preparation of test solution: Prior to the preparations of the application solutions, the total amount of the 14C-labelled test substance (about 1 mg) was dissolved in accurately 10 mL of acetone. Thereafter, the amount of radioactive material present was determined by LSC (Liquid Scintillation Counting) to be 1.0195 mg. For this purpose, appropriate aliquots of the stock solution were transferred into volumetric flasks and diluted with acetone to the intended concentrations.The activity of these solutions was checked by LSC.
- Equilibration Test: The equilibration time was determined in preliminary tests with all soils at the highest intended test concentration of about 0.05 μg/mL which is about 50% of the water solubility of the test substance. Equilibrium was reached already after 2 hours.
- Addition of Test Substance: For each soil, 1 g of air-dry material was weighed into tarred centrifuge tubes and suspended with 100 mL of 0.01 mol CaCl2-solution. Portions of 0.1 mL of the treatment solutions were added to the test vessels, resulting in initial test concentrations between 0 (blank) and about 0.05 μg/mL. Finally, the total weight was determined.

Duration:

2 h

Initial conc. measured:

>= 0.003 - <= 0.051 other: mg/L

Temp.:

20 °C

Duration:

4 h

Temp.:

20 °C

Remarks:

2 hours per desorption procedure, procedure was repeated once

Key result

Sample No.:

#1

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

62 357 L/kg

pH:

7

Temp.:

20 °C

Matrix:

Loamy sand

% Org. carbon:

0.77

Key result

Sample No.:

#2

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

74 833 L/kg

pH:

5.7

Temp.:

20 °C

Matrix:

Sand

% Org. carbon:

0.43

Key result

Sample No.:

#3

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

11 888 L/kg

pH:

5.7

Temp.:

20 °C

Matrix:

silt loam

% Org. carbon:

1.39

Key result

Sample No.:

#4

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

44 714 L/kg

pH:

7.1

Temp.:

20 °C

Matrix:

silt loam

% Org. carbon:

4.39

Key result

Sample No.:

#5

Type:

Koc

Remarks:

Freundlich Coefficient

Value:

12 117 L/kg

pH:

6.6

Temp.:

20 °C

Matrix:

Humic soil

% Org. carbon:

19.4

Sample No.:

#1

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

474 L/kg

Temp.:

20 °C

pH:

7

Matrix:

Loamy sand

% Org. carbon:

0.77

Remarks on result:

other: result of desorption 1; desorption 2 is an outlier

Sample No.:

#2

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

219 L/kg

Temp.:

20 °C

pH:

5.7

Matrix:

sand

% Org. carbon:

0.43

Remarks on result:

other: result of desorption 1; desorption 2 is an outlier

Sample No.:

#3

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

533 L/kg

Temp.:

20 °C

pH:

5.7

Matrix:

silt loam

% Org. carbon:

1.39

Remarks on result:

other: result of desorption 1; desorption 2 is an outlier

Sample No.:

#4

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

4 017 L/kg

Temp.:

20 °C

pH:

7.1

Matrix:

silt loam

% Org. carbon:

4.39

Remarks on result:

other: result of desorption 1; desorption 2 is an outlier

Sample No.:

#5

Phase system:

solids-water in soil

Type:

other: Koc - Desorption Freundlich Coefficient

Value:

3 304 L/kg

Temp.:

20 °C

pH:

6.6

Matrix:

humic soil

% Org. carbon:

19.4

Remarks on result:

other: result of desorption 1; desorption 2 is an outlier

Adsorption and desorption constants:

An overivew of the results is provided in Table 8 - Table 9 in 'Any other information on results incl. tables'
- Adsorption and Desorption Isotherms: The adsorption constants k were in the range between 166 μg/g of soil Les Evouettes and 2350 μg/g of soil for the humic soil (lliarsaz). These results demonstrate a very strong adsorption of the test substance onto soil particles. The slopes 1/n for the adsorption isotherms were with the exception of soil Les Evouettes with values between 0.9954 to 1.0636 close to unity, indicating that the Freundlich adsorption isotherms would follow the distribution law. Only in soil Les Evouettes the slope was 0.8149. When related to the organic carbon content (koc) or to the organic matter content (Q-value) figures ranging from 11888 to 74833 μg/g of organic carbon and from 6896 to 43407 μg/g organic matter, respectively, were found.
On the average, the corresponding values were 38758 and 22482 μg/g of organic carbon and organic matter, respectively. These data clearly classify the test substance as a strongly adsorbing pesticide as e.g. fluorodifen or parathion. Desorption constants of the first desorption step ranged from 219 to 4017 μg/g of soil and for the second desorption step from 157 to 7026 μg/g of soil. When compared with the adsorption values they were significantly higher indicating a partial irreversibility of the adsorption of the test substance.

Recovery of test material:

An overview of the results is provided in Table 3 - Table 7 in 'Any other information on results incl. tables'
- Recovery (Samples 2 - 6): The total recovery ranged, on the average, between 89.2 and 93.1% of the radioactivity applied. The amount of radioactivity found to be adsorbed to soil particles ranged, on the average, from 11.06 (Lakeland sand) to 81.01 % (lliarsaz humic soil) of the dose applied. The amount of radioactivity found in the aqueous phases of soil Lakeland was, on the average, 18.74, 14. 84 and 4.68% for the ad sorption step, desorption step 1 and desorption step 2, respectively. The corresponding figures for soil Illarsaz were 4.37, 2.01 and 1.23%. Considerable amounts of radioactivity were found to be adsorbed to glass-walls accounting for 39.86 and 3.7 % for Lakeland and Illarsaz soil, respectively.
- Recovery (Samples 6'): Total recoveries of these samples worked-up after the adsorption step ranged from 92.44 to 102.96 % of the dose applied. In supernatant aqueous phases, extractables of soil sediment, residual soil and washings of glass-wares the range of radioactivity was 4.22 - 18.11, 72.51 - 97.24, 0.53 - 1.93 and 0.09 - 1.43 %, respectively.

Sample no.:

#1

Duration:

2 h

% Adsorption:

36.04

Remarks on result:

other: in soil

Sample no.:

#2

Duration:

2 h

% Adsorption:

11.06

Remarks on result:

other: in soil

Sample no.:

#3

Duration:

2 h

% Adsorption:

50.45

Remarks on result:

other: in soil

Sample no.:

#4

Duration:

2 h

% Adsorption:

76.91

Remarks on result:

other: in soil

Sample no.:

#5

Duration:

2 h

% Adsorption:

81.01

Remarks on result:

other: in soil

Remarks on result:

not measured/tested

Transformation products:

not measured

Details on results (Batch equilibrium method):

- Rate of adsorption (equilibration test): The equilibration time was established with all test soils by measuring the decrease in radioactivity in the supernatant aqueous phase after various incubation times for up to 180 minutes. The initial concentration used was 0.05 μg/mL test solution. Already after 85 minutes of shaking at 20 °C the concentration of a.i. in the supernatant water phase reached steady state conditions for all samples. Based on these findings it was decided to run the whole study with an equilibration time of 2 hours.
- Analysis of Radioactivity: When the aqueous phases of samples 6' after the adsorption were analysed it was found that in sandy soils the parent compound amounted to 99.1 to about 100 % and in the humic soil (Illarsaz) to 91.6 %. In the aqueous phase of the latter soil only impurity I was found which relatively increased in the aqueous phase due to the fact that it is adsorbed only to a minor extent because of its higher polarity.

Table 3. Balance of Radioactivity with Soil Collombey after Adsorption and Desorption

Sample Number	Soil Ads	Aqueous Phase			Glassware (*)	Extractable	Non- extractable	Recovery
		Ads	Des1	Des2
2	39.18	15.23	4.90	7.06	23.98	0.00	0.00	90.36
3	36.17	18.37	4.29	7.78	22.34	0.00	0.00	88.96
4	34.31	12.62	6.08	6.45	30.58	0.00	0.00	90.06
5	35.43	21.16	6.10	5.14	21.63	0.00	0.00	89.46
6	35.09	14.59	8.48	5.11	25.15	0.00	0.00	88.42
Average	36.04	16.40	5.97	6.31	24.74	0.00	0.00	89.45
6'	0.00	17.26	0.00	0.00	1.43	72.51	1.23	92.44

(*) Radioactivity adsorbed to glasswall of incubation tubes finally removed by extraction with acetone.

 

Table 4. Balance of Radioactivity with Soil Lakeland after Adsorption and Desorption

Sample Number	Soil Ads	Aqueous Phase			Glassware (*)	Extractable	Non- extractable	Recovery
		Ads	Des1	Des2
2	12.70	20.15	15.54	4.67	33.30	0.00	0.00	86.36
3	11.94	16.96	13.08	3.43	40.89	0.00	0.00	86.30
4	8.83	19.49	16.94	3.58	43.52	0.00	0.00	92.37
5	12.53	17.84	14.64	5.50	37.38	0.00	0.00	87.90
6	9.31	19.26	14.00	6.24	44.19	0.00	0.00	93.00
Average	11.06	18.74	14.84	4.68	39.86	0.00	0.00	89.19
6'	0.00	15.38	0.00	0.00	0.70	76.01	0.53	92.62

(*) Radioactivity adsorbed to glasswall of incubation tubes finally removed by extraction with acetone

 

Table 5. Balance of Radioactivity with Soil Les Evouettes after Adsorption and Desorption 

Sample Number	Soil Ads	Aqueous Phase			Glassware (*)	Extractable	Non- extractable	Recovery
		Ads	Des1	Des2
2	52.52	13.77	7.32	6.95	7.59	0.00	0.00	88.16
3	48.54	13.22	9.10	4.21	13.98	0.00	0.00	89.05
4	53.92	7.04	6.30	4.04	21.74	0.00	0.00	93.05
5	49.34	11.95	8.43	4.63	17.79	0.00	0.00	92.13
6	47.93	21.00	6.96	5.06	12.96	0.00	0.00	93.91
Average	50.45	13.40	7.62	4.98	14.81	0.00	0.00	91.26
6'	0.00	18.11	0.00	0.00	0.41	77.07	1.8	97.38

(*) Radioactivity adsorbed to glasswall of incubation tubes finally removed by extraction with acetone.

 

Table 6. Balance of Radioactivity with Soil Vetroz after Adsorption and Desorption

Sample Number	Soil Ads	Aqueous Phase			Glassware (*)	Extractable	Non- extractable	Recovery
		Ads	Des1	Des2
2	77.22	4.57	3.34	2.85	3.45	0.00	0.00	91.44
3	76.11	5.24	3.50	2.26	3.84	0.00	0.00	90.96
4	75.58	3.34	3.02	2.01	9.58	0.00	0.00	93.53
5	77.13	5.16	3.39	3.08	4.46	0.00	0.00	93.23
6	78.50	3.70	2.70	1.77	9.68	0.00	0.00	96.35
Average	76.91	4.40	3.19	2.40	6.20	0.00	0.00	93.10
6'	0.00	5.44	0.00	0.00	0.09	95.39	1.93	102.86

(*) Radioactivity adsorbed to glasswall of incubation tubes finally removed by extraction with acetone

  

Table 7. Balance of Radioactivity with Soil Illarsaz after Adsorption and Desorption

Sample Number	Soil Ads	Aqueous Phase			Glassware (*)	Extractable	Non- extractable	Recovery
		Ads	Des1	Des2
2	80.70	3.92	1.94	0.98	3.80	0.00	0.00	91.33
3	79.77	5.12	1.92	1.51	3.71	0.00	0.00	92.02
4	80.89	4.21	1.98	1.07	3.02	0.00	0.00	91.17
5	80.18	4.32	2.13	1.36	4.25	0.00	0.00	92.24
6	83.51	4.28	2.08	1.22	3.74	0.00	0.00	94.83
Average	81.01	4.37	2.01	1.23	3.70	0.00	0.00	92.32
6'	0.00	4.22	0.00	0.00	0.41	97.24	1.09	102.96

(*) Radioactivity adsorbed to glasswall of incubation tubes finally removed by extraction with acetone

 

Table 8. Freundlich Constants, Slopes and Correlation Coefficients for the Adsorption of the test substance by various Soils at 20 °C.

Soil type	Organic matter (%)	k (Freundlich constant)	KFOC	Q-values
Lakeland	0.74	321	74833	43407
Collombey	1.33	481	62357	36170
Les Evouettes	2.40	166	11888	6896
Vetroz	7.57	1963	44714	25936
Illarsaz	33.43	2350	12117	7029
Average			41182	23888

 

Table 9. Freundlich Constants, Slopes and Correlation Coefficients for the desorption of the test substance by various Soils at 20 °C

Soil Type	Organic Matter (%)	Desorption 1			Desorption 2
		1/n	kdes1	r2	1/n	kdes2	r2
Lakeland	0.74	1.0423	219	0.9891	0.8699	157	0.9573
Collombey	1.33	0.9116	474	0.9939	1.2799	5916 a	0.9726
Les Evouettes	2.40	0.9423	533	0.9791	0.9830	1019	0.9698
Vetroz	7.57	1.0433	4017	0.9852	1.0801	7026	0.9508
lllarsaz	33.43	0.9635	3304	0.9995	0.9363	4236	0.9806

a. Desorption 2 is considered to be an outlier. Due to the high amount of radioactivity adsorbed to glass-walls in the sandy soils (e.g. 24.74% for soil Collombey) a partial desorption from the glass-wall instead off  desorption from the soil must be assumed, thus leaving higher x/m-values than expected. This assumption 1s supported by the slope (1/n=l.3) of the desorption isotherm.

Validity criteria fulfilled:

yes

Conclusions:

In an OECD TG 106 followed adsorption/desorption study, Freundlich coefficients (KFOC) were calculated to be 62357, 74833, 11888, 44714 and 12117 L/kg in Collombey (Loamy sand), Lakeland (sand), Les Evouettes (Silt loam), Vetroz (silt loam) and Illarsaz (Humic) soils, respectively.

Executive summary:

The adsorption and desorption properties of [14C-difluorophenyl ring]-labelled test substance were studied in five soils: Collombey (Loamy sand), Lakeland (sand), Les Evouettes (Silt loam), Vetroz (silt loam) and Illarsaz (Humic soil). The study was performed in accordance with OECD TG 106 and EPA 163-1 guideline, and in compliance with GLP criteria. A preliminary test showed that 2 hours incubation is sufficient to achieve equilibrium in the adsorption phase. In the definitive test, a solution to soil ratio of 100:1 (100mL 0.01M CaCl2 solution to 1 g of soil) was used for all soils. The test substance was applied at 5 concentrations ranging between about 0.00254 and 0.05071 μg/mL. In addition, one untreated control sample (vehicle only) was set up. The test tubes were shaken for 2 hours in the dark at 20°C to establish equilibration. After equilibration, the soil and aqueous layers were separated until the supernatant was clear. Aliquots of the aqueous layer were taken for LSC then the remaining supernatant was removed and the tubes with wet soil reweighed. The first desorption step was conducted by adding 0.01M CaCl2 solution (100 mL), weighing the samples then shaking for a further two hours in the dark at 20 ± 1°C. A second desorption step was performed in an identical manner to the first. The radioactivity in the extracts was determined by LSC and in the extracted soil by combustion. The acetone was concentrated and analysed by LSC and TLC. The aqueous phase was partitioned twice with dichloromethane and the radioactivity in each phase quantified by LSC. After concentration, the dichloromethane phase was analysed by TLC.

Overall recoveries of applied radioactivity ranged from 89.2 - 93.1%. The test substance was strongly bound to soil and to the walls of the sample tubes, which had to be rinsed with acetone at the end of the experiment to obtain a mass balance. The distribution coefficient (Kd) was directly related to the amount of organic carbon in the soil for values of OC from 0.43 - 4.39%. Beyond this point further increases in OC did not affect the degree of adsorption. Freundlich adsorption constants KF were calculated to be 62357, 74833, 11888, 44714 and 12117 L/kg in Collombey (Loamy sand), Lakeland (sand), Les Evouettes (Silt loam), Vetroz (silt loam) and Illarsaz (Humic) soils, respectively. The mean adsorption constant KFOC is 41182. These values characterise the test substance as a very strongly adsorbing (immobile) compound.

Description of key information

Arithmetic mean Log Koc = 4.61 L/kg (Koc = 41182 L/kg) based on a study covering 5 soils, equilibrium batch method, OECD TG106 and EPA guideline 163 -1 followed, Ellgehausen, 1992.

Key value for chemical safety assessment

Koc at 20 °C:

41 182

Additional information

There is one study available for this endpoint. The study followed OECD TG 106 and EPA 163 -1 guideline, and was in compliance with GLP criteria (Reliability 1). It covered 5 types of soil and used the equilibrium batch method. The soil types, test conditions, and results are summarised in the table below.

Table 1. Summary of the Kfoc values for the substance

USDA	Name / Origin	OC*	pH	Kf*	KFOC*	1/n	Author/year
Loamy sand	Collombey, CH	0.77	7.0	481	62357	1.0401	Ellgehausen,1992
Sand	Lakeland, US	0.43	5.7	321	74833	1.0636	Ellgehausen,1992
Silt loam	Les Evouettes, CH	1.39	5.7	166	11888	0.8149	Ellgehausen,1992
Silt loam	Vetroz, CH	4.39	7.1	1963	44714	0.9954	Ellgehausen,1992
Humic soil	Illarsaz, CH	19.4	6.6	2350	12117	1.0045	Ellgehausen,1992
Arithmetic mean Koc					41182