5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-(ethylsulfinyl)-1H-pyrazole-3-carbonitrile

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

16 Dec 2003 - 16 Feb 2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted in 2000

Deviations:

yes

Remarks:

The soils used in the study are those required by Brazilian Environmental Agency (IBAMA) and are different from those requested by OECD 106.

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministry of Health, Welfare and Sport, The Netherlands, 22 Apr 2002

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

Test tubes were incubated under shaking at 19 - 21 °C.

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: HPLC
- Type: HP 1090
- Type, material and dimension of analytical (guard) column: Phenomenex Lichrospher RP18, 250 mm x 4.6 mm, 5 µm
- Detection system: Diode Array Detector and Flow Scintillation Detector

MOBILE PHASES
- Type: methanol:0.1% H3PO4 in gradient, 10:90 rising linearly to 90:10 at 30 min

REFERENCE SUBSTANCES
- Identity:

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 0.3 µg

REPETITIONS
- Number of determinations:

EVALUATION
- Calculation of capacity factors k':
- Calculation of retention times:
- Determination of the log Koc value:

Details on matrix:

COLLECTION AND STORAGE
- Geographic location:
(1) Typic Humaquept: 22°35'12'' S/47°35'34" W, natural pasture/hygrophyte area, never exposed to pesticide treatments;
(2) Rhodic Hapludox: 22°45'06" S/47°34'O1" W, was cultivated with sugar cane and received application of isoxaflutole and ametryn in the last 12 months;
(3) Typic Hapludox: 22°50'17" S/47°37'31" W, was cultivated with sugar cane and received application of isoxaflutole and ametryn in the last 12 months
- Sampling depth (cm): 0 - 20 cm
- Soil preparation: air-dried and sieved using a 2 mm mesh

PROPERTIES (1)
- Soil texture: 24% sand, 21% silt, 54% clay
- Soil taxonomic classification: Typic Humaquept
- Soil classification system: USDA, 1998
- pH (CaCl2): 4.9
- Soil organic matter (g/kg): 79
- CEC (meq/100 g): 21.4

PROPERTIES (2)
- Soil texture: - Soil texture: 41% sand, 6% silt, 53% clay
- Soil taxonomic classification: Rhodic Hapludox
- Soil classification system: USDA, 1998
- pH (CaCl2): 5.2
- Soil organic matter (g/kg): 36
- CEC (meq/100 g): 9.7

PROPERTIES (3)
- Soil texture: - Soil texture: 82% sand, 4% silt, 14% clay
- Soil taxonomic classification: Typic Hapludox
- Soil classification system: USDA, 1998
- pH (CaCl2): 4.6
- Soil organic matter (g/kg): 24
- CEC (meq/100 g): 6.3

Details on test conditions:

TEST CONDITIONS
- Buffer: 10 mM CaCl2

TEST SYSTEM
- Type, size and further details on reaction vessel: Teflon tubes, tightly capped
- Method of preparation of test solution: see Table 1.
- Adsorption: 1.0 g of soil and 10 mL of each treatment solution were conditioned in centrifuge tubes. Afterwards, the soils were transferred into centrifuge tubes which were tightly capped and were shaken vigorously for several seconds with a vortex mixer. Then, tubes were shaken horizontally in a mechanic shaker (180 rpm, 1 h), at constant temperature (19 to 21 °C). Subsequently, tubes were centrifuged at 6000 rpm, for 5 minutes. Two 1-mL aliquots were taken from the supernatant and added into the scintillation vials containing 10 mL of scintillation cocktail for radioactivity measurement.
- Desorption: After the adsorption step, the supernatant was drained and 10 mL of fresh 10 mM CaCl2 solution was added to the soils. Tubes were shaken again in a mechanic shaker (180 rpm, 1 h), at constant temperature (19 to 21 °C). Afterwards, tubes were centrifuged at 6000 rpm for 5 minutes. Two 1-mL aliquots were taken from the new supernatant and added into the scintillation vials containing 10 mL of scintillation cocktail. Radioactivity in the new equilibrium solution was measured.

Sample No.:

#1

Duration:

1 h

Sample No.:

#2

Duration:

1 h

Sample No.:

#3

Duration:

1 h

Type:

Koc

Value:

109.4

Remarks on result:

other: Mean Koc value, 19 - 21 °C

Type:

Kd

Value:

6.3

Remarks on result:

other: Soil #1, 19 - 21 °C

Type:

Kd

Value:

1.63

Remarks on result:

other: Soil #2, 19 - 21 °C

Type:

Kd

Value:

1.57

Remarks on result:

other: Soil #3, 19 - 21 °C

Details on results (HPLC method):

- Adsorption data: The percentages adsorbed of Ethiprole ranged between 35.31% and 40.82%, 11.69% and 16.01%, and 11.91% and 15.37% for soil no. 1, 2 and 3, respectively.
- Desorption data: The percentages desorbed ranged between 41.25% and 45.36%, 55.28% and 60.54% and 54.19% and 59.76% for soil no. 1, 2 and 3, respectively.
- Total radioactivity recovery ranged from 97.97% to 99.10%.

- A preliminary screening test showed that there was no significant adsorption on the test vessel. Based on HPLC analysis, the test substance was found to be stable in the treatment solution over 73 h.

- Mass balance in the adsorption/desorption test: Soil (1) 99.10% ± 1.29%, soil (2) 98.65% ± 0.66%, soil (3) 97.97% ± 0.65%

- The Koc values for the single soil samples were 137.4 (soil #1), 78.0 (soil #2) and 112.7 (soil #3).

Validity criteria fulfilled:

not applicable

Reference 2

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption/desorption

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 Oct - 12 Nov 1997

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: FIFRA, 40 CFR Part 158, Subdivision N, 163-1 (2)

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1981

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1 °C

Analytical monitoring:

yes

Details on matrix:

COLLECTION AND STORAGE
- Geographic location:
(195) Clay loam: Northwood ND, USA
(198) Sandy loam: Madera CA, USA
(199) Silty clay loam: Stuttgart AR, USA
(204) Sandy loam: Pond at Columbia MO, USA
(205) Loam: Northwood ND, USA
- Soil preparation: The soils were sieved through a standard 2-mm mesh screen before using

PROPERTIES (195)
- Soil texture: 25% sand, 45% silt, 30% clay
- Soil taxonomic classification: Clay loam
- Soil classification system: USDA
- pH: 6.4
- Organic matter (%): 4.9
- CEC (meq/100 g): 27.4
- Bulk density (g/cm3): 1.00

PROPERTIES (198)
- Soil texture: 58% sand, 30% silt, 12% clay
- Soil taxonomic classification: Sandy loam
- Soil classification system: USDA
- pH: 7.5
- Organic matter (%): 0.6
- CEC (meq/100 g): 5.3
- Bulk density (g/cm3): 1.35

PROPERTIES (199)
- Soil texture: 14% sand, 56% silt, 30% clay
- Soil taxonomic classification: Silty clay loam
- Soil classification system: USDA
- pH: 5.0
- Organic matter (%): 2.4
- CEC (meq/100 g): 13.4
- Bulk density (g/cm3): 1.12

PROPERTIES (204)
- Soil texture 62% sand, 28% silt, 10% clay
- Soil taxonomic classification: Sandy loam
- Soil classification system: USDA
- pH: 7.9
- Organic matter (%): 1.6
- CEC (meq/100 g): 26.1
- Bulk density (g/cm3): 1.17

PROPERTIES (205)
- Soil texture: 38% sand, 38% silt, 24% clay
- Soil taxonomic classification: Loam
- Soil classification system: USDA
- pH: 6.3
- Organic matter (%): 5.7
- CEC (meq/100 g): 27.6
- Bulk density (g/cm3): 1.03

Details on test conditions:

TEST CONDITIONS
- Buffer: 0.01 M CaCl2
- pH:
- Suspended solids concentration:
- other:

TEST SYSTEM
- Type, size and further details on reaction vessel: 15 or 50 mL borosilicate glass culture tubes with teflon lined screw caps. For container adsorption determination 50 mL teflon centrifuge tubes were also used.
- Water filtered: yes, tap water used was demineralised, passed over ion-exchange resin beds, purified by a Milli-Q system and finally passed through a 0.2 µm filter unit.
- Amount of soil and water per treatment (if simulation test): 2000 g dry weight equivalents of soils 195 and 205 and 5000 g dry weight equivalents of soils 198, 199 and 204 were used. 0.327, 0.336, 0.572, 0.164 and 0.273 mL of water were added to the soils 195, 198, 199, 204 and 205, respectively.
- Soil-water ratio (if simulation test): Soil: water ratio of 1:5 for soils #195 and 205 and 1:2 for soils #198, 199 and 204
- Number of reaction vessels/concentration: 2
- Equipment: The sample tubes were agitated on a platform shaker located in a 20 ± 1 °C Environmental Chamber for the adsorption and desorption equilibration periods. Samples were stored at 4 °C prior to analysis. Centrifugation for separation of the liquid and solid phases was accomplished using an IEC Centra-HN benchtop centrifuge. Liquid aliquots were measured and transferred using varying sizes of Hamilton syringes, or using a 1000 µL adjustable volume electronic pipette, a 100 µL adjustable volume Eppendorf auto-pipette, or 200 µL adjustable volume Oxford auto-pipette.
- Test performed in closed vessels: yes

Sample No.:

#1

Duration:

24 h

Initial conc. measured:

0.05 other: µg/mL

Sample No.:

#2

Duration:

24 h

Initial conc. measured:

0.15 other: µg/mL

Sample No.:

#3

Duration:

24 h

Initial conc. measured:

0.5 other: µg/mL

Sample No.:

#4

Duration:

24 h

Initial conc. measured:

1 other: µg/mL

Type:

Koc

Value:

123

Temp.:

20 °C

Remarks on result:

other: Mean Koc value

Type:

Kd

Value:

4.17

Temp.:

20 °C

% Org. carbon:

4.9

Remarks on result:

other: Soil #195

Type:

Kd

Value:

0.366

Temp.:

20 °C

% Org. carbon:

0.6

Remarks on result:

other: Soil #198

Type:

Kd

Value:

1.45

Temp.:

20 °C

% Org. carbon:

2.4

Remarks on result:

other: Soil #199

Type:

Kd

Value:

1.12

Temp.:

20 °C

% Org. carbon:

1.6

Remarks on result:

other: Soil #204 (Sediment)

Type:

Kd

Value:

4.65

Temp.:

20 °C

% Org. carbon:

5.7

Remarks on result:

other: Soil #205

Duration:

24 h

% Adsorption:

> 97.8 - < 102.4

Details on results (Batch equilibrium method):

PRELIMINARY TESTS
- Container Adsorption: The percent of the test substance adsorbed to the container walls after 24 h of equilibration in 50 mL teflon centrifuge tubes, 15 mL borosilicate glass culture tubes, and silanized 15 mL borosilicate glass culture tubes was 0.098, -0.491, and -0.786 percent, respectively. Adsorption to all tube types is insignificant and borosilicate tubes were chosen for the test.
- Filter Adsorption: Filter adsorption was determined on a variety of syringe filters. It was found that adsorption of the test substance to the Whatman 0.2 µm PVDF syringe filter (7%) was insignificant when solutions were diluted 1:4 (v:v) acetonitrile:dosing solution.

OTHER
- The Koc values ranged from 104 to 147 in the five soil samples tested and showed good correlation to the organic matter content which ranged from 0.6 to 5.7 in the five soils.
- The test substance was stable during the course of the study.

Table 1: Summary of the adsorption results.

 

Soil Matrix	Organic Matter (%)	Soil:Water	14C Mass Balance	Adsorbed (%)	Kd	Koc	Correlation (r)
195	4.9	1:5	99.4 ± 1.9	52.1 ± 5.3	4.17	147	0.9983
198	0.6	1:2	99.0 ± 1.4	18.1 ± 2.9	0.37	105	0.9984
199	2.4	1:2	99.9 ± 2.5	45.8 ± 4.0	1.45	104	0.9999
204	1.6	1:2	102.4 ± 4.4	38.0 ± 2.0	1.12	121	0.9996
205	5.7	1:5	97.8 ± 1.7	56.2 ± 6.4	4.65	140	0.9961

  

Table 2: Summary of the desorption results.

 

Soil Matrix	Desorbed (%)			Not Desorbed (%)
	Wash 1	Wash 2	Wash 3	Wash 1	Wash 2	Wash 3
195	37.4 ± 4.1	30.9 ± 4.3	25.5 ± 3.9	62.6 ± 4.1	69.1 ± 4.3	74.5 ± 3.9
198	72.0 ± 5.9	56.8 ± 7.9	40.9 ± 9.2	28.0 ± 5.9	43.2 ± 7.9	59.1 ± 9.2
199	45.6 ± 4.9	37.1 ± 4.5	30.2 ± 4.1	54.4 ± 4.9	62.9 ± 4.5	69. 8 ± 4.1
204	56.2 ± 2.5	48.5 ± 3.1	41.7 ± 4.0	43.8 ± 2.5	51.5 ± 3.1	58.3 ± 4.0
205	32.2 ± 4.3	25.9 ± 4.3	21.5 ± 3.5	67.8 ± 4.3	74.1 ± 4.3	78.5 ± 3.5

 

Validity criteria fulfilled:

not applicable

Description of key information

log Koc = 2.09

Key value for chemical safety assessment

Koc at 20 °C:

123

Additional information

The mobility of the substance in soil can be estimated based on its sorption constant. Two GLP studies are available for the substance. The first study employed a batch equilibrium method according to FIFRA guideline 40 CFR Part 158, Subdivision N, 163-1 (2). Freundlich adsorption constants normalised to the organic carbon (OC) content Koc were determined for the substance in five different soils at 20 °C with values ranging from 104 to 147 (mean values: Koc 123, log Koc 2.09).

This result is supported by a second study applying a batch equilibrium method according to OECD guideline 106 with three soil types different from those required by the guideline. Freundlich adsorption constants Koc were determined with values ranging from 78 to 137 (mean values: Koc 109, log Koc 2.04).