5,7-dichloro-4-(4-fluorophenoxy)quinoline;quinoxyfen (ISO)

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: U.S. EPA Pesticide Assessment Guidelines Subdivision N, 163-1

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Name of substance: DE-795-quinoline-2-14C
Lot number: RS-12391
Radiochemical purity: 98.6%

Radiolabelling:

yes

Test temperature:

25 ± 1°C

Analytical monitoring:

yes

Details on sampling:

- Adsorption Phase Sampling
Adsorption samples were removed from the shaker and chamber after 48 hours of equilibration. The test and blank samples were centrifuged. Triplicate 1-mL aliquots of the test, blank, and control supernatants were analyzed by LSC. Each blank. test, and control supernatant was decanted into a 4-oz amber bottle containing 14 mL of acetonitrile and sonicated for approximately 10 minutes. Each test sample soil pellet was then weighed. For the 0.020 µg/ml. samples, the test supernatant for soil M588 was filtered and analyzed by HPLC, along with the dose solutions and control supernatants.
A volume of 0.01 M CaCl2 equal to the volume of adsorption supernatant removed was added back to each test sample. The test samples were recapped, weighed, and returned to the shaker and chamber.
- Desorption Phase Sampling
The desorption samples were analyzed after an additional 48 hours of desorption equilibration. The test samples were removed from the shaker and centrifuged. Triplicate 1-mL aliquots of the supernatants were analyzed by LSC. Each test supernatant was decanted into a 4-oz amber bottle containing 14 mL of acetonitrile and sonicated for approximately 10 minutes. Each test sample soil pellet was then weighed.

Matrix no.:

#1

Matrix type:

loam

% Clay:

18

% Silt:

42

% Sand:

40

% Org. carbon:

1.4

pH:

5.4

CEC:

8.4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.2

Matrix no.:

#2

Matrix type:

sandy loam

% Clay:

13

% Silt:

26

% Sand:

61

% Org. carbon:

0.7

pH:

8.3

CEC:

13.6 meq/100 g soil d.w.

Bulk density (g/cm³):

1.03

Matrix no.:

#3

Matrix type:

sand

% Clay:

6

% Silt:

4

% Sand:

90

% Org. carbon:

0.64

pH:

6.4

CEC:

4 meq/100 g soil d.w.

Bulk density (g/cm³):

1.4

Matrix no.:

#4

Matrix type:

loam

% Clay:

24

% Silt:

36

% Sand:

40

% Org. carbon:

4.2

pH:

4.7

CEC:

23.5 meq/100 g soil d.w.

Bulk density (g/cm³):

0.92

Matrix no.:

#5

Matrix type:

clay

% Clay:

68

% Silt:

24

% Sand:

8

% Org. carbon:

1.3

pH:

7.2

CEC:

38.7 meq/100 g soil d.w.

Bulk density (g/cm³):

1.18

Details on matrix:

Four North American soils and one U.S. sediment were used to determine the mobility potential of the test substance. The soils selected were USDA characterized as a loam (M576), sand (M588), loam M590), and clay (M599). The sediment was designated as M582 and was USDA characterized as a sandy loam.

Details on test conditions:

TEST CONDITIONS
- ABC Reagent water: The reagent water used in this study was demineralized and purified using a Millipore Milli-Q purification water system. The water is equivalent to or better than ASTM Type II water and has a resistivity greater than 10 megohm.cm.
ABC reagent water was used to prepare 0.01 M CaCl2 solution. The 0.01 M CaCl2 solution was prepared by dissolving 5.88 g CaCl2.2H20 into 4.0 liters of ABC reagent water.

TEST SYSTEM
- 40-mL borosilicate glass culture tubes with Teflon lined screw caps. The sample tubes were agitated on a reciprocating platform shaker in an environmental chamber set to maintain 25 ± 1°C.
- Soil Preparation: Aliquots of soil [0.400 g dry weight equivalents] were weighed into separate 60 tared 40-mL borosilicate glass culture tubes for each soil type (except soil M590 in which 50 tubes were generated). A 0.010 and 0.088-mL aliquot of 0.01 M CaCl2 was added to each aliquot of soil M582 and soil M599, respectively, to bring the moisture content to 75% field moisture capacity (FMC) at 1/3 bar. The tubes were capped and stored in the environmental chamber when not in use. Prior to use, the total soil plus tube weights were measured.

Duration:

48 h

Temp.:

>= 24 - <= 26 °C

Remarks:

For all type of samples at 0.002 to 0.020 µg/mL concentrations

Duration:

48 h

Temp.:

25 °C

Computational methods:

- Adsorption and desorption coefficients (Kd): [total µg adsorbed (based on total radioactivity)/ dry weight of the soil (g)]/concentration of the test substance in the adsorption phase (µg/ml)
- Adsorption coefficient per organic carbon (Koc): (Kd x 100)/Organic Carbon %

Key result

Sample No.:

#1

Type:

Kd

Value:

745 other: mL/g

pH:

5.4

Temp.:

25 °C

Matrix:

Loam

% Org. carbon:

1.4

Remarks on result:

other: Standard deviation: 132 mL/g

Key result

Sample No.:

#2

Type:

Kd

Value:

429 other: mL/g

pH:

8.3

Temp.:

25 °C

Matrix:

Sandy loam

% Org. carbon:

0.7

Remarks on result:

other: Standard deviation: 80 mL/g

Key result

Sample No.:

#3

Type:

Kd

Value:

290 other: mL/g

pH:

6.4

Temp.:

25 °C

Matrix:

Sand

% Org. carbon:

0.64

Remarks on result:

other: Standard deviation: 79 mL/g

Key result

Sample No.:

#4

Type:

Kd

Value:

3 147 other: mL/g

pH:

4.7

Temp.:

25 °C

Matrix:

Loam

% Org. carbon:

4.2

Remarks on result:

other: Standard deviation: 165 mL/g

Key result

Sample No.:

#5

Type:

Kd

Value:

971 other: mL/g

pH:

7.2

Temp.:

25 °C

Matrix:

Clay

% Org. carbon:

1.3

Remarks on result:

other: Standard deviation: 181 mL/g

Key result

Sample No.:

#1

Type:

Koc

Value:

53 400 other: mL/g

pH:

5.4

Temp.:

25 °C

Matrix:

Loam

% Org. carbon:

1.4

Remarks on result:

other: Standard deviation: 9450 mL/g

Key result

Sample No.:

#2

Type:

Koc

Value:

61 500 other: mL/g

pH:

8.3

Temp.:

25 °C

Matrix:

Sandy loam

% Org. carbon:

0.7

Remarks on result:

other: Standard deviation: 11500 mL/g

Key result

Sample No.:

#3

Type:

Koc

Value:

45 300 other: mL/g

pH:

6.4

Temp.:

25 °C

Matrix:

Sand

% Org. carbon:

0.64

Remarks on result:

other: Standard deviation: 12400 mL/g

Key result

Sample No.:

#4

Type:

Koc

Value:

75 200 other: mL/g

pH:

4.7

Temp.:

25 °C

Matrix:

Loam

% Org. carbon:

4.2

Remarks on result:

other: Standard deviation: 3940 mL/g

Key result

Sample No.:

#5

Type:

Koc

Value:

75 900 other: mL/g

pH:

7.2

Temp.:

25 °C

Matrix:

Clay

% Org. carbon:

1.3

Remarks on result:

other: Standard deviation: 14100 mL/g

Adsorption and desorption constants:

Definitive adsorption Koc values of 5.34E+04, 6.15E+04, 4.53E+04, 7.52E+04, 7.59E+04 mL/g for soils M576, M582, M588, M590, and M599, respectively, classify the test substance as immobile.

Recovery of test material:

The adsorption of the test substance was not completely reversible and that the test substance may not freely desorb from the test soil once bound. Overall 14C-mass balance was good (generally between 94% and 103%), although the 0.08 µg/ml. Samples for soil M590 were observed to be below <90% (as low as 80.5%). However, the mean 14C-mass balance for each soil type was in the range of 90-110 percent indicating that there was no consistent loss of 14C-material during the definitive study.

Sample no.:

#1

Duration:

48 h

% Adsorption:

88.2

Sample no.:

#2

Duration:

48 h

% Adsorption:

81.1

Sample no.:

#3

Duration:

48 h

% Adsorption:

73.9

Sample no.:

#4

Duration:

48 h

% Adsorption:

97

Sample no.:

#5

Duration:

48 h

% Adsorption:

90.6

Sample no.:

#1

Duration:

48 h

% Desorption:

7.99

Sample no.:

#2

Duration:

48 h

% Desorption:

13.3

Sample no.:

#3

Duration:

48 h

% Desorption:

17.8

Sample no.:

#4

Duration:

48 h

% Desorption:

1.84

Sample no.:

#5

Duration:

48 h

% Desorption:

6.05

Transformation products:

no

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- The preliminary test was conducted at a 0.02 µg/ml nominal test substance concentration at a 1:20, w:w, soil:water ratio for soils M576, M582, M588, M590, and M599. Equilibration times were established by sampling of duplicate samples for each soil type and for soil-less controls at 2, 8, 24 and 48 hours after initiation. These results show that the majority of adsorption occurred within the first two hours of equilibration. After the 2-hour time point, only minor changes in supernatant concentration <5%) between each time point were observed. The equilibration time was set at 48 hours since mass balance was successfully determined at that time point.
The stability of the test substance during the preliminary test was established by analyzing the dosing solution, 48-hour control supernatants, and 48-hour filtered soil extract concentrates. The HPLC fractionation histograms show consistency in peak shape and retention time of the test substance in the concentrated soil extracts. At least 93% of 14C-test substance was recovered from all samples injected.
The percent adsorbed, estimated Kd, estimated Koc, and 14C-mass-balance for each soil type and equilibration time were calculated. The results for equilibration times showed that the mean percent adsorbed values for soils M576, M582, M588, M590, and M599 at the 48 hour time point were 97.1, 95.9, 93.5, 99.1, and 97.9%, respectively, which were not within the ideal 20-80 percent adsorbed range at the tested soil:water ratio. The range for mean estimated Kd for the 48 hour samples was 290 to 2206 mL/g, while the mean estimated Koc for the 48 hour samples ranged from 4.54E+04 to 7.41E+04 mL/g for all soils tested. The mean 14C-mass balance (48-hour time point) for M576, M582, M588, M590 and M599 was 107.4, 106.2, 103.2, 103.0, and 111.2%, respectively.

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Yes
- Experimental conditions maintained throughout the study: Yes

RESIDUES
- HPLC: The dosing solution analysis and control solution analysis showed mean percentages of 98.9 and 99.1 % recovered activity as 14C-test substance, respectively. Analysis of the adsorption phase supernatants for the two replicates of M588 showed 95.3 and 100%, respectively, recovered activity as 14C-test substance. Analysis of the soil extracts showed recoveries of 94.5 to 98.4% recovered activity as 14C-test substance. The mean HPLC column recoveries during the extracted test sample analysis ranged from 98.5 to 108.9%).
- TLC: TLC analysis showed that greater than 90% of the recovered 14C-activity observed in the extracted samples was test substance. The mean TLC plate recoveries for all sample data utilized ranged from 89.4 to 103% of the applied activity.

Statistics:

Statistics utilized in this study included means, standard deviations, least squares linear regression (including 95% confidence intervals), and minimum quantifiable limits. Correlation coefficients were calculated for all linear regressions. Sufficient replication was planned to control bias.

Validity criteria fulfilled:

yes

Conclusions:

Definitive adsorption Koc values classify the test substance as immobile.
The percent adsorbed was higher than the percent desorbed which indicated that adsorption was not readily reversible.
HPLC analysis of the dosing solution, control supernatants, adsorption supernatants showed that >90% of the 14C-activity was recovered as the test substance.

Executive summary:

A soil adsorption-desorption study was conducted with the test substance on five different soils at 25 ± 1°C using the batch equilibrium method as suggested in the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), 40 CFR Part 158, Subdivision N-163-1.

Four North American soils and one U.S. sediment were used to determine the mobility potential of the test substance. The soils selected were USDA characterized as a loam (M576), sand (M588), loam M590), and clay (M599). The sediment was designated as M582 and was USDA characterized as a sandy loam.

Based on the results of the preliminary tests for the test substance, the definitive test adsorption and desorption equilibration times were set at 48 hours. The definitive test was conducted at five nominal test substance concentrations for all soils, with the exception that 0.002 µg/ml level was not performed on M590 because quantitation of the test substance in the adsorption supernatants would be less than the MQL for the LSC analysis. The nominal concentrations were 0.00 (blank), 0.002, 0.008, 0.012, 0.016, and 0.020 µg/ml in 0.01 M CaCl2. A 1:100, w:w; soil:water ratio was used for all soils.

Definitive adsorption Koc values of 5.34E+04, 6.15E+04, 4.53E+04, 7.52E+04, 7.59E+04 mL/g for soils M576, M582, M588, M590, and M599, respectively, classify the test substance as immobile. These soils demonstrated similarities of n values between the adsorption/desorption phases, which indicated that sorption to soil had a dependence on the test chemical concentration. Also, the percent adsorbed was higher than the percent desorbed which indicated that adsorption was not readily reversible. A correlation between the adsorption Kd and organic matter content of the soil was observed, however when organic matter in the soils were similar, the contribution of clay content was also significant. The wide range of Koc values indicate that sorption of the test substance was not completely dependent on the organic carbon content and clay content of the soil matrices. Other factors that may influence sorption are pH and cation exchange capacity (CEC) but the extent of that influence was not quantifiable.

HPLC analysis of the dosing solution, control supernatants, adsorption supernatants for M588, and soil extract concentrates (after adsorption and after desorption) showed that >90% of the 14C-activity was recovered as the test substance. Co-chromatography was performed on selected samples and showed co-elution of the test substance in the soil extracts with radiolabeled test substance.

Reference 2

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:

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

Deviations:

yes

Remarks:

Calculations for Kd were not carried out because good data was obtained from the Freundlich equation for Kads, In addition, since the values obtained for 1/N were almost linear then Kd would approximate to Kads in any case.

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Specific details on test material used for the study:

Name of substance: [14C]-XDE-795
Batch number: GHD-3058-19
Radiochemical purity: 99%

Radiolabelling:

yes

Remarks:

Labelled at position 2 of the quinoline ring

Analytical monitoring:

yes

Details on sampling:

After 16 hours shaking, the tubes were removed from the shaker and centrifuged at 2500 rpm for 10 minutes. The supernatants were removed, weighed and then subjected to LSC analysis (6mI for adsorption, 9mI for desorption) to determine the concentration of radioactivity in solution at equilibrium.
For the adsorption experiment, the blank supernatant samples (6 ml) were analysed by LSC to give a mean background value of radioactivity for subtraction, and the controls (6 ml) analysed to determine any adsorption to glass. For the desorption experiment, blank 0.01 M CaCl2 solution (9 ml) was similarly analysed by LSC to give a background value.

Matrix no.:

#1

Matrix type:

sandy clay loam

% Clay:

28

% Silt:

22

% Sand:

50

% Org. carbon:

1.7

pH:

8.3

CEC:

48 meq/100 g soil d.w.

Matrix no.:

#2

Matrix type:

loamy sand

% Clay:

7

% Silt:

12

% Sand:

81

% Org. carbon:

2.1

pH:

6.1

CEC:

21 meq/100 g soil d.w.

Matrix no.:

#3

Matrix type:

loamy sand

% Clay:

9

% Silt:

7

% Sand:

84

% Org. carbon:

1.5

pH:

6.5

CEC:

8.4 meq/100 g soil d.w.

Details on matrix:

The soils were a standard Speyer 2.2 (loamy sand) obtained from Speyer, Germany, and two UK agricultural soils obtained from Marcham, Oxon (sandy clay loam) and Wereham, Norfolk (Loamy sand).
The soils were partially air-dried, sieved to 2 mm and stored at ca 4°C until required. Before use the moisture content was determined by oven-drying portions of each soil for 24 hours at 105°C and calculating the weight loss.

Details on test conditions:

TEST SYSTEM
- Type, size and further details on reaction vessel: Glass jars (500 mI capacity)
- Number of reaction vessels/concentration: 2
- Method of preparation of test solution: [14C]-test substance, as supplied, was dissolved in acetone to give an active ingredient concentration of between 221-226 µg/mI. This was used as a further acetone dilution (to ca 10 µg/ml), or else directly for all other experiments. The solutions were stored in the dark at <16°C prior to use.

Duration:

16 h

Remarks:

The results from the LSC analysis of the adsorbates showed that equilibrium was reached at or before 16 hours for all three soils, with no significant change in the 16-18 hour period.

Key result

Sample No.:

#1

Type:

Koc

Value:

21 550 dimensionless

pH:

8.3

Matrix:

Marcham sandy clay loam

% Org. carbon:

1.7

Remarks on result:

other: Log10 Koc: 4.33

Key result

Sample No.:

#2

Type:

Koc

Value:

18 339 dimensionless

pH:

6.1

Matrix:

Speyer 2.2 loamy sand

% Org. carbon:

2.1

Remarks on result:

other: Log10 Koc: 4.26

Key result

Sample No.:

#3

Type:

Koc

Value:

28 897 dimensionless

pH:

6.5

Matrix:

Wereham loamy sand

% Org. carbon:

1.5

Remarks on result:

other: Log10 Koc: 4.46

Key result

Sample No.:

#1

Type:

other: Kads

Value:

366 dimensionless

pH:

8.3

Matrix:

Marcham sandy clay loam

% Org. carbon:

1.7

Key result

Sample No.:

#2

Type:

other: Kads

Value:

385 dimensionless

pH:

6.1

Matrix:

Speyer 2.2 loamy sand

% Org. carbon:

2.1

Key result

Sample No.:

#3

Type:

other: Kads

Value:

433 dimensionless

pH:

6.5

Matrix:

Wereham loamy sand

% Org. carbon:

1.5

Adsorption and desorption constants:

Treatment of the adsorption data obtained using the Freundlich equation gave adsorption constants (Kads) of 366, 385 and 433 for the Marcham sandy clay loam, Speyer 2.2 loamy sand and Wereham loamy sand soils respectively.

Recovery of test material:

The amount of radioactivity in the adsorbate, desorbates, acetone soil extracts and soil residue derived from the nominal 0.05 µg/ml experiment was calculated and expressed as % of the mean applied radioactivity to show the overall recovery for each soil type. The results showed that, within experimental limits, a radiochemical balance (100-107%) was achieved for the various procedures. The majority of the radioactivity (>90%) for each soil type was recovered in the acetone extracts of the soil obtained after the second desorption cycle, and it is for this reason that the stability experiment was carried out on these samples and not the adsorbates, since they contained 1% or less of the applied radioactivity.

Concentration of test substance at end of desorption equilibration period:

The adsorption was largely irreversible since the desorption cycles failed to desorb any significant amounts (≤1%) of the radioactivity that had become associated with the soil.

Transformation products:

no

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Adsorption to test apparatus: The result from the LSC analysis of the zero-time sample showed that the [14C]-test substance concentration was 0.0486 µg/mI, which is close to the nominal value. Then after shaking for 18 hours between 97-99% of the zero-time radioactivity could be accounted for, indicating there to be minimal adsorption of [14C]-test substance to glass.
- Stability under test conditions (No soil): The extraction procedure used to remove radioactivity from aqueous solution remaining at the end of the 18-hour adsorption to test apparatus experiment was shown to be quantitative (94-98%). Subsequent TLC analysis of this radioactivity showed it to comprise of one component which matched non-radiolabeled test substance, indicating stability of the test material under the experimental conditions with no soil present.
- Determination of equilibrium time: The results from the LSC analysis of the nominal 0.05 µg/mI dosing solution confirmed that solubility of [14C]-test substance at this concentration was achieved.


MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Stable
- Experimental conditions maintained throughout the study: Yes

Validity criteria fulfilled:

yes

Conclusions:

Test substance have no potential for movement through soil, with two desorption cycles showing that adsorption was largely irreversible.

Executive summary:

The sorption characteristics of the test substance have been investigated in three types of the soils (Marcham sandy clay loam, Speyer 2.2 loamy sand and Wereham loamy sand). The study was conducted to OECD Guideline 106 to comply with EC Directive 91/414/EEC.

The results from the adsorption test, using [14C]-labeled test substance at four concentrations between 0.005-0.05 µg/ml in 0.01 M CaCl2 and calculated according to the Freundlich equation.

Treatment of the adsorption data obtained using the Freundlich equation gave adsorption constants (Kads) of 366, 385 and 433 for the Marcham sandy clay loam, Speyer 2.2 loamy sand and Wereham loamy sand soils respectively. The Freundlich adsorption isotherms had slopes (1/N) ranging from 0.974 to 0.999.

The values for Kads and log10 Koc indicate that the test substance will have no potential for movement through soil, with two desorption cycles showing that adsorption was largely irreversible.

A radiochemical balance was demonstrated for the nominal 0.05 µg/ml experiment, as was the stability of the test substance throughout the experiment.

Description of key information

In one study, the definitive adsorption Koc values classified the test substance as immobile. The percent adsorbed was higher than the percent desorbed which indicated that adsorption was not readily reversible. In a second study, the test substance had no potential for movement through soil, with two desorption cycles showing that adsorption was largely irreversible.