thiacloprid (ISO);(Z)-3-(6-chloro-3-pyridylmethyl)-1,3-thiazolidin-2-ylidenecyanamide;{(2Z)-3-[(6-chloropyridin-3-yl)methyl]-1,3-thiazolidin-2-ylidene}cyanamide

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Dec 1993 - Feb 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: (U.S.) Environmental Protection Agency, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate, § 163-1 Leaching and Adsorption/Desorption Studies

Version / remarks:

1988

GLP compliance:

yes (incl. QA statement)

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 ± 1°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: The adsorptions/desorption measurements were carried out with 4 different concentrations of active ingredient corresponding to 0.130 mg, 0.099 mg, 0.065 mg and 0.013 mg test substance/L CaCl2-solution.
- Sampling interval: Treated with the application solutions of different concentrations, samples were processed after shaking for 24 hours.

Matrix no.:

#1

Matrix type:

other: Sandy loam; soil identification: Borstel, Germany

% Clay:

6.9

% Silt:

21.5

% Sand:

71.6

% Org. carbon:

1.15

pH:

6.3

Matrix no.:

#2

Matrix type:

other: Sandy loam; soil identification: Howe, IN

% Clay:

8.2

% Silt:

26.3

% Sand:

65.5

% Org. carbon:

0.75

pH:

7.1

Matrix no.:

#3

Matrix type:

other: Silt clay loam; soil identification: Stanley, KS

% Clay:

42

% Silt:

41

% Sand:

17

% Org. carbon:

1.05

pH:

5.6

Matrix no.:

#4

Matrix type:

other: Sand; soil identification: Vero Beach, FL

% Clay:

1

% Silt:

0.3

% Sand:

98.7

% Org. carbon:

0.2

pH:

5.1

Matrix no.:

#5

Matrix type:

other: Sandy loam; soil identification: Graoe Vineyard, CA

% Clay:

5.9

% Silt:

30.2

% Sand:

64

% Org. carbon:

0.45

pH:

6.7

Matrix no.:

#6

Matrix type:

other: Loam; soil identification: Napa, CA

% Clay:

24.1

% Silt:

48.1

% Sand:

27.8

% Org. carbon:

0.99

pH:

7.7

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: The tests were carried out using the following soils: Borstel from Borstel near Hannover, Germany (sandy loam); Howe from Indiana, USA (sandy loam); Stanley from Kansas, USA (silty clay loam); Vero Beach from Florida, USA (sand); Grape Vineyard from California, USA (sandy loam); Napa from California, USA (loam)
- Sampling depth (cm): Samples were taken from the top soil layers (0-30 cm).
- Storage conditions: The soil Borstel was removed from the field on June 21, 1991 and stored in the climatic cabinet at +4°C in the dark. The soils Stanley, Vero Beach, Grape Vineyard and Napa were obtained from Miles Inc, South Metcalf, Stillwell, KS (USA) before the beginning of the test. The soil Howe is kept in wooden boxes under vegetation in the field and was removed before the beginning of the test.
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): The soil moisture was determined in all soils after screening to < 2 mm.

PROPERTIES
- Soil texture: Information on the soil properties may be taken from the Table “Matrix properties”.

Details on test conditions:

TEST CONDITIONS
Adsorption measurements:
- The adsorptions/desorption measurements were carried out with 4 different concentrations of active ingredient corresponding to 0.130 mg, 0.099 mg, 0.065 mg and 0.013 mg test substance/L CaCl2-solution.
- Mercury chloride (50 mg HgCl2/L) was added to the applications solutions as biocide in order to prevent a possible biotic degradation of the active ingredient. Additional adsorption/desorption measurements without addition of mercury were carried out with the highest concentration of active ingredient for control purposes (individual determinations).
- Portions of 6 g each (relative to dry weight) of the soils were weighed into centrifuge tubes, treated with the application solutions of different concentrations and shaken for 24 hours.

Desorption measurements:
- The remaining soil was treated with 20 ml 0.01 M CaCl2-solution (stock solution I) and shaken once for another 24 hours.
- After centrifugation (15 minutes, about 6000 g) the radioactivity content of the clear supernatant was determined.
- This desorption step was carried out a total of 4 times at the highest concentration (0.130mg/L) in each case.
- The content of unchanged parent compound was determined chromatographically from the solution of the highest concentration of active ingredient of the first desorption step. The radioactivity measurement of the soil was carried out by combustion.

Sample No.:

#1

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

6.3

Temp.:

20 °C

Sample No.:

#2

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

7.1

Temp.:

20 °C

Sample No.:

#3

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

5.6

Temp.:

20 °C

Sample No.:

#4

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

5.1

Temp.:

20 °C

Sample No.:

#5

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

6.7

Temp.:

20 °C

Sample No.:

#6

Duration:

24 h

Initial conc. measured:

> 0.013 - < 0.13 other: mg/L CaCl2

pH:

7.7

Temp.:

20 °C

Sample no.:

#1

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

6.3

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Sample no.:

#2

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

7.1

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Sample no.:

#3

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

5.6

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Sample no.:

#4

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

5.1

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Sample no.:

#5

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

6.7

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Sample no.:

#6

Duration:

24 h

Conc. of adsorbed test mat.:

0.13 other: mg/L CaCl2

pH:

7.7

Temp.:

20 °C

Remarks:

This desorption step was carried out a total of 4 times at the highest concentration (0.130 mg/L CaCl2) for each soil.

Computational methods:

The adsorption coefficient K as a measure for the adsorption behavior was described by the adsorption isotherm according to Freundlich.

In x/m = 1/n In C + In K

In this equation x is the amount of active ingredient (µg) adsorbed to the soil, m is the amount of soil (g) and C is the equilibrium concentration of the active ingredient in the aqueous solution (µg/mL).

Sample No.:

#1

Type:

Koc

Value:

393 L/kg

pH:

6.3

Temp.:

20 °C

Matrix:

Borstel

% Org. carbon:

1.15

Sample No.:

#2

Type:

Koc

Value:

753 L/kg

pH:

7.1

Temp.:

20 °C

Matrix:

Howe

% Org. carbon:

0.75

Sample No.:

#3

Type:

Koc

Value:

522 L/kg

pH:

5.6

Temp.:

20 °C

Matrix:

Stanley

% Org. carbon:

1.05

Sample No.:

#4

Type:

Koc

Value:

572 L/kg

pH:

5.1

Temp.:

20 °C

Matrix:

Vero Beach

% Org. carbon:

0.2

Sample No.:

#5

Type:

Koc

Value:

870 L/kg

pH:

6.7

Temp.:

20 °C

Matrix:

Grape Vineyard

% Org. carbon:

0.45

Sample No.:

#6

Type:

Koc

Value:

582 L/kg

pH:

7.7

Temp.:

20 °C

Matrix:

Napa

% Org. carbon:

0.99

Remarks on result:

other:

Remarks:

Please see "Appendices 6-11" in the Attached backgound material.

Remarks on result:

other:

Remarks:

Please see "Appendices 6-11" in the Attached backgound material.

Transformation products:

not specified

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- The preliminary test showed in all soils a low dependence of the adsorption rate from the soil/water ratio. Based on these results the weighed amounts of soil were defined for all soils to be 6 g and the amount of shaking solution was defined to be 20 ml for the further tests.
- The time for the establishment of the equilibrium between the test substance concentration in the solution and the part being adsorbed to the soil phase was determined in a preliminary test. The time until achievement of the equilibrium is defined as the time span from the beginning of the test until the point of time at which the concentration of the solution remains constant within an interval of 24 hours or does not change by more than 5%. The results show that an equilibrium has been established already after a short period of time (Appendix 5). In the main test for the determination of the adsorption/desorption data a uniform shaking period of 24 hours was defined for all soils.

MAIN TEST: PERFORMANCE
- Other observations: The shaking tests with the application solution without addition of soil (mean recovery = 98%) and the total accountabilities (4.2 establishment of the equilibrium) with recovery rates between 98.5% and 102.9% show that no essential adsorption occurred at the walls of the sample vessels.

TRANSFORMATION PRODUCTS
- The chromatographic analysis of the clear centrifuged supernatants of the soils after establishment of the equilibrium showed that almost the entire measured radioactivity (> 98%) could be assigned to the unchanged parent compound.
- Between 85% and 94% of the measured radioactivity only could be determined as parent compound (TLC).

RESIDUES
- Extractable residues (% of applied amount at end of study period): The proportion of active ingredient being adsorbed to soil Borstel ranged from 68% to 76% as a function of the applied concentrations of active ingredient (Appendix 6), that of soil Howe ranged from 74% to 81% (Appendix 7), that of soil Stanley from 67% to 70% (Appendix 8), that of soil Vero Beach from 30 to 34% (Appendix 9), that of soil Grape Vineyard from 64% to 71% (Appendix 10) and that of soil Napa from 76% to 83% (Appendix 11). The Appendices 6 – 11 are provided in the “Attached background material”.
- An average of 2-4% less radioactivity were adsorbed to all soils in the control tests without addition of biocide HgCh (highest concentration of active ingredient).
- The Koc values of the adsorption phase ranged from 393 to 870 among the different soils.
- The Koc values of the desorption phase ranged from 491 to 1009 among the different soils.
- The desorption tests showed desorption rates of 15-67% as a function of the respective concentrations of active ingredient (Appendices 6-11).

Validity criteria fulfilled:

not applicable

Description of key information

logKoc = 2.59 – 2.94 L/kg (geom. mean: 2.78 L/kg)

Key value for chemical safety assessment

Koc at 20 °C:

596

Additional information

In an experimental study following GLP and “(U.S.) Environmental Protection Agency, Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate, § 163-1 Leaching and Adsorption/Desorption Studies”, Freundlich adsorption constants of (Z)-3-(6-chloro-3-pyridylmethyl)-1,3-thiazolidin-2-ylidenecyanamide related to organic carbon content (Koc) ranged from 393 to 870 L/kg (geom. mean: 596 L/kg). logKoc = 2.59 – 2.94 L/kg.