reaction mass of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-2H -isothiazol-3-one

Adsorption / desorption

Administrative data

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

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2006

Report date:

2006

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

January 2006

Deviations:

no

GLP compliance:

yes

Type of method:

batch equilibrium method

Media:

soil

Test material

Test material information

Constituent 1

Test material form:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Rohm and Haas, Batch No. 1063.0009

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: 96.9%
- Specific activity: 48.5 mCi/g
- Locations of the label: 14C label was at the 4 and 5 position

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Not described
- Stability under test conditions: Confirmation of parent stability examined by TLC
- Solubility and stability of the test substance in the solvent/vehicle: Water solubility > 1000 ppm
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: 14C MIT, 29.43 mg (1.43 mCi or 52.8 MBq) was initially dissolved in 25 ml of sterile deionized water (nominal 1000 mg/L). A test concentrate solution was prepared by adding the above stock solution to a solution of 0.01M CaCl2.
- Final dilution of a dissolved solid, stock liquid or gel: 5 mg 14C-MIT/L solution with 0.01M CaCl2

FORM AS APPLIED IN THE TEST (if different from that of starting material)
Liquid

Radiolabelling:

yes

Study design

Test temperature:

Not described

Batch equilibrium or other method

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 5 mg/L
- Sampling interval: 2, 4, 8, 24, and 48 hrs
- Sample storage before analysis: Not described

Matrix properties

Matrix properties 1

Matrix no.:

#1

Matrix type:

sandy loam

% Clay:

15

% Silt:

17

% Sand:

68

% Org. carbon:

1.3

pH:

6.2

CEC:

11.5 meq/100 g soil d.w.

Matrix properties 2

Matrix no.:

#2

Matrix type:

clay loam

% Clay:

36

% Silt:

22

% Sand:

42

% Org. carbon:

3.9

pH:

6.5

CEC:

27.4 meq/100 g soil d.w.

Matrix properties 3

Matrix no.:

#3

Matrix type:

silty clay loam

% Clay:

31

% Silt:

57

% Sand:

12

% Org. carbon:

2.1

pH:

5

CEC:

13.8 meq/100 g soil d.w.

Matrix properties 4

Matrix no.:

#4

Matrix type:

sand

% Clay:

4

% Silt:

4

% Sand:

92

% Org. carbon:

0.3

pH:

4.7

CEC:

1.8 meq/100 g soil d.w.

Matrix properties 5

Matrix no.:

#5

Matrix type:

loam

% Clay:

20

% Silt:

36

% Sand:

44

% Org. carbon:

16.8

pH:

7.4

CEC:

60.4 meq/100 g soil d.w.

Details on matrix:

COLLECTION AND STORAGE
- Geographic location:
Hyde Farm Pickneys Green, Maidenhead, Berks, UK (sandy loam)
Pickett Piece Manor Farm, Oxfordshire, UK (clay loam)
Naldrett Farm Wisborough Green, Sussex, UK (silty clay loam)
Lillifield Wishanger Farm, Churt, Surrey, UK (sand)
Kenny Hill Farm, Mildenhall, Suffolk, UK (loam)
- Sampling depth (cm): Top 20 cm of agricultural land
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Air dried, passed through a 2 mm sieve, and sterilized by gamma irradiated prior to use

Details on test conditions:

TEST CONDITIONS
- Buffer: No
- pH: 6.2 (sandy loam), 6.5 (clay loam), 5.0 (silty clay loam), 4.7 (sand) and 7.4 (loam)

TEST SYSTEM
- Type, size and further details on reaction vessel: 50 ml PTFE centrifuge tubes
- Water filtered (i.e. yes/no; type of size of filter used, if any): No
- Amount of soil/sediment/sludge and water per treatment (if simulation test): 20 g of one of the five soils was added and 20 ml of 5mg 14C-MIT/L of 0.01M CaCl2
- Soil/sediment/sludge-water ratio (if simulation test): 1:1
- Number of reaction vessels/concentration: 3
- Measuring equipment: Liquid scintillation counter, Thin layer chromatography
- Test performed in closed vessels due to significant volatility of test substance: No
- Test performed in open system: Yes
- Method of preparation of test solution: Dilution in matrix
- Are the residues from the adsorption phase used for desorption: Yes

Duration of adsorption equilibration

Duration of adsorption equilibration 1

Duration:

2 h

Initial conc. measured:

5 other: mg/L

Duration of adsorption equilibration 2

Duration:

4 h

Initial conc. measured:

5 other: mg/L

Duration of adsorption equilibration 3

Duration:

8 h

Initial conc. measured:

5 other: mg/L

Duration of adsorption equilibration 4

Duration:

24 h

Initial conc. measured:

5 other: mg/L

Duration of adsorption equilibration 5

Duration:

48 h

Initial conc. measured:

5 other: mg/L

Duration of desorption equilibration

Duration of desorption equilibration 1

Sample no.:

#1

Duration:

2 h

Conc. of adsorbed test mat.:

0.525 other: mg/L

pH:

6.2

Remarks:

Sandy loam

Duration of desorption equilibration 2

Sample no.:

#2

Duration:

2 h

Conc. of adsorbed test mat.:

1.235 other: mg/L

pH:

6.5

Remarks:

Clay loam

Duration of desorption equilibration 3

Sample no.:

#3

Duration:

2 h

Conc. of adsorbed test mat.:

0.8 other: mg/L

pH:

5

Remarks:

Silty clay loam

Duration of desorption equilibration 4

Sample no.:

#4

Duration:

2 h

Conc. of adsorbed test mat.:

0.095 other: mg/L

pH:

4.7

Remarks:

Sand

Duration of desorption equilibration 5

Sample no.:

#5

Duration:

2 h

Conc. of adsorbed test mat.:

2.3 other: mg/L

pH:

7.4

Remarks:

Loam

Results and discussion

Adsorption coefficient

Adsorption coefficient 1

Key result

Sample No.:

#1

Type:

Kd

Value:

0.1 dimensionless

pH:

6.2

Matrix:

Sandy loam

% Org. carbon:

1.3

Adsorption coefficient 2

Key result

Sample No.:

#2

Type:

Kd

Value:

0.27 dimensionless

pH:

6.5

Matrix:

Clay loam

% Org. carbon:

3.9

Adsorption coefficient 3

Key result

Sample No.:

#3

Type:

Kd

Value:

0.14 dimensionless

pH:

5

Matrix:

Silty clay loam

% Org. carbon:

2.1

Adsorption coefficient 4

Key result

Sample No.:

#4

Type:

Kd

Value:

0.03 dimensionless

pH:

4.7

Matrix:

Sand

% Org. carbon:

0.3

Adsorption coefficient 5

Key result

Sample No.:

#5

Type:

Kd

Value:

1.07 dimensionless

pH:

7.4

Matrix:

Loam

% Org. carbon:

16.8

Adsorption coefficient 6

Key result

Sample No.:

#1

Type:

Koc

Value:

7.7 dimensionless

pH:

6.2

Matrix:

Sandy loam

% Org. carbon:

1.3

Adsorption coefficient 7

Key result

Sample No.:

#2

Type:

Koc

Value:

6.9 dimensionless

pH:

6.5

Matrix:

Clay loam

% Org. carbon:

3.9

Adsorption coefficient 8

Key result

Sample No.:

#3

Type:

Koc

Value:

6.7 dimensionless

pH:

5

Matrix:

Silty clay loam

% Org. carbon:

2.1

Adsorption coefficient 9

Key result

Sample No.:

#4

Type:

Koc

Value:

10 dimensionless

pH:

4.7

Matrix:

Sand

% Org. carbon:

0.3

Adsorption coefficient 10

Key result

Sample No.:

#5

Type:

Koc

Value:

6.4 dimensionless

pH:

7.4

Matrix:

Loam

% Org. carbon:

16.8

Results: Batch equilibrium or other method

Adsorption and desorption constants:

Koc (adsorption) = 7.7 (sandy loam), 6.9 (clay loam), 6.7 (silty clay loam), 10 (sand) and 6.4 (loam)

Recovery of test material:

The range of average recoveries was 90.4% to 119.1%

Mass balance (%) at end of desorption phase

Mass balance (%) at end of desorption phase 1

Sample no.:

#1

Duration:

2 h

% Desorption:

34.3

Remarks on result:

other: Sandy loam

Mass balance (%) at end of desorption phase 2

Sample no.:

#2

Duration:

2 h

% Desorption:

16.7

Remarks on result:

other: Clay loam

Mass balance (%) at end of desorption phase 3

Sample no.:

#3

Duration:

2 h

% Desorption:

10.6

Remarks on result:

other: Silty clay loam

Mass balance (%) at end of desorption phase 4

Sample no.:

#4

Duration:

2 h

% Desorption:

26.3

Remarks on result:

other: Sand

Mass balance (%) at end of desorption phase 5

Sample no.:

#5

Duration:

2 h

% Desorption:

14.7

Remarks on result:

other: Loam

Transformation products:

not measured

Remarks:

Due to the low concentration the degradation products were not determined.

Details on results (Batch equilibrium method):

PRELIMINARY TEST
- Weighed soil: 20, 4 or 0.8 g per 20 mL CaCl2 solution
- Volume of CaCl2 solution: 20 mL
- Test substance concentration in final solution: 5 mg/L
- Analytical test substance concentration in final solution: 5 mg/L

MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: Yes
- Experimental conditions maintained throughout the study: Yes
- Buffer/test substance interactions affecting sorption: No
- Further chemical interactions: No
- Buffer-catalyzed degradation of test substance: No

RESULTS OF SUPPLEMENTARY EXPERIMENT (if any): PTFE centrifuge tubes were chosen for all experiments as there was no significant adsorption to this material. At a soil:solution ratio of 1:25, there was essentially no adsorption of MIT to either soil. There was a slight adsorption at a ratio of 1:5 for the loam soil but again essentially none for the clay loam. At a soil:solution ratio of 1:1 both soils showed significant adsorption. Thus a ratio of 1:1 was employed for all further experiments.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The study provided is satisfactory to describe the mobility of MIT in soil. According to the US EPA classification scheme, MIT is considered highly mobile. However, due to its rapid biodegradation in soil (half-life is 6.5 hours), it is unlikely that parent mobility will be an environmental concern.

Executive summary:

The test guideline followed was OECD 106. There were no deviations from this test guideline. All five soils were gamma irradiated prior to dosing to enhance sterility and prevent biodegradation of MIT during the course of the experiment.Initially¹⁴C-MIT was added to 50 ml PTFE centrifuge tubes and it was determined that after 48 hours of mixing there was no significant adsorption to the containers. A second experiment to determine the soil:solution ratio was performed with the clay loam and loam soils. Ratios examined were 1:1, 1:5, and 1:25 and the MIT concentration was 5 mg/L. After 22 hours the samples were radioassayed to determine the amount of MIT adsorbed to the soil. A third experiment determined the kinetics of adsorption for all five soils at a soil:solution ratio of 1:1 and dosing with 5mg¹⁴C-MIT/L 0.01M CaCl₂. Samples were radioassayed after 2, 4, 8, 24, and 48 hrs of equilibration. A fourth experiment was performed to determine the desorption parameters of MIT. Five soils were dosed with 5 mg¹⁴C-MIT/L 0.01M CaCl₂and after 2 hrs of equilibration the¹⁴C solution was removed and replaced with 0.01M CaCl₂. After 2, 4, 24, and 48 hours of mixing, the amount of¹⁴C-activity desorbed was determined by radioassay. In the final experiment, the isotherm parameters were determined in all 5 soils and using dosing concentrations of 5, 1, 0.2, 0.04, and 0.008 mg¹⁴C-MIT/L 0.01M CaCl₂. After 2 hours the concentration of¹⁴C activity in the solution and sediment phases was determined. In addition, the mass balance was determined for these samples.Aliquots from the soil:solution and the kinetic experiments were analyzed by TLC to determine stability of MIT. MIT was not highly adsorbed to any of the 5 soils examined. The system was found to reach equilibrium within 2 hrs and under these conditions MIT was stable in these soil:solution systems. It was determined that a soil:solution ratio of 1:1 was necessary since there was marginal if any soil adsorption at ratios of 1:5 and 1:25. Mass balance was determined for the clay loam and loam soils and the average recovery 92.66 ± 3.44% and 107.17 ± 15.11%, respectively.

After a 2 hour equilibration period in the kinetics test the percent¹⁴C-activity detected as MIT by TLC ranged from 88.9% (loam) to 97.3% (silty clay loam and soil-less control). Due to the low concentration the degradation products were not determined.

The study provided is satisfactory to describe the mobility of MIT in soil. According to the US EPA classification scheme, MIT is considered highly mobile. However, due to its rapid biodegradation in soil (half-life is 6.5 hours), it is unlikely that parent mobility will be an environmental concern.