1,3,5-Triazine-2,4-diamine, N2-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-(1-fluoroethyl)-

Adsorption / desorption

Link to relevant study record(s)

Reference

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:

no

Qualifier:

according to guideline

Guideline:

other: US EPA Guideline Subdivision N, Section 163-1

Qualifier:

according to guideline

Guideline:

other: Canadian PMRA DACO Number 8.2.4.2

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Umwelt, Raumordnung und Landwirtschaft des Landes NRW, 40190 Düsseldorf, Germany

Type of method:

batch equilibrium method

Media:

soil

Radiolabelling:

yes

Test temperature:

20 +/- 1°C

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Test concentrations of 1.0, 0.3, 0.1, 0.03 and 0.01 mg/L
- Sampling interval: Samples were taken after 24 hours (adsorption) and 24 hours (first desorption step)
- Sample storage before analysis: Samples were analyzed immediately after sampling.

Details on matrix:

COLLECTION AND STORAGE
- Geographic location: 3 soils from Germany; 2 soils from US (see table 1). All soils were taken agricultural used areas. They are well known from different metabolism and sorption studies.
- Sampling depth (cm): 0 - 20 cm
- Storage conditions: The soil was stored (air dried) at about 5°C for max. about 1 year (soil Pikevile).
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): Soils were sieved to a particle size of <= 2 mm

PROPERTIES: see table 1

Details on test conditions:

TEST CONDITIONS
- Buffer: 0.01M aqueous CaCl2 solution


TEST SYSTEM
- Study design for the adsorption phase see table 2; study design for desorption phase see table 3
- Type, size and further details on reaction vessel: Teflon centrifuge tubes, 42 mL volume
- Method of preparation of test solution: The application solution A was prepared by transferring 2300 µL of the stock solution of the test item (29.6 MBq/5 mL; pure radiolabelled substance) into a volumetric gas flask. Following 230 mL of 0.01 M CaCl2 solution was added and sonificated. The solution was analysed by LSC and HPLC. The application solutions B to E were prepared by appropriate dilutions of the application solution A.
- Other: Preliminary tests: The determination of the adequate soil-to-solution ratio, the determination of adequate equilibration time, the determination of test material stability and the test to determine the adsorption of the test substance to the test vessels were conducted as requested in the Guideline prior to the definitive test. The results were incorporated in the study design of the definitive tests (see table 2). No adsorption of the test substance to the surface of the test vessels was observed. The test item was stable in control samples without soil. After incubation for 96 hours only two minor degradation products were determined with max. 1% of the injected RA.

Duration:

24 h

Initial conc. measured:

>= 0.01 - <= 1 other: mg/L

pH:

6

Temp.:

20 °C

Duration:

24 h

Temp.:

20 °C

Computational methods:

- Freundlich adsorption and desorption coefficients: Calculations according to OECD Guideline 106
- Adsorption coefficient per organic carbon (Koc): Based on Freundlich Kf-value the respective Freundlich Koc-value was determined

Type:

Koc

Value:

426

Temp.:

20 °C

% Org. carbon:

2

Remarks on result:

other: Soil AXXa

Type:

Koc

Value:

395.8

Temp.:

20 °C

% Org. carbon:

2.4

Remarks on result:

other: Soil HaH

Type:

Koc

Value:

468.2

Temp.:

20 °C

% Org. carbon:

1.3

Remarks on result:

other: Soil WuW

Type:

Koc

Value:

741.8

Temp.:

20 °C

% Org. carbon:

1.5

Remarks on result:

other: Soil Pik

Type:

Koc

Value:

449.7

Temp.:

20 °C

% Org. carbon:

2.3

Remarks on result:

other: Soil SSC

Adsorption and desorption constants:

See table 4 for Freundlich parameters.

Recovery of test material:

The overall material balance for all concentrations was in the range of 101.2 - 104.1% (mean: 102.5%) of the applied radioactivity. Thus, it was demonstrated that no significant RA dissipated from the test vessels or was lost during processing.

Transformation products:

not measured

Details on results (Batch equilibrium method):

The pH values or the supernatant after establishing the equilibrium (24 hours) are:
Soil AXXA: pH 6.5
Soil HaH: pH 6.8
Soil WuW: pH 5.9
Soil Pik: pH 5.9
Soil SSC: pH 6.3
There is no significant correlation between pH and adsorption.

Statistics:

Arithmetic means were used for LSC measurements, standard deviation was calculated for the values according to the Standardised Report Format.
Linear regression was used to determine the Freundlich values.
Outlier rejection criteria were not used.

Table 4: Adsorption and desorption constants in the soils

Soil Type	Adsorption				Desorption
	Kf [mL/g]	1/n	R²	Koc [mL/g]	Kf [mL/g]	1/n	R²	Koc [mL/g]
AXXa	8.5	0.867	0.9998	426.0	11.4	0.859	0.9995	569.3
HaH	9.5	0.885	0.9998	395.8	13.0	0.876	0.9997	542.3
WuW	6.1	0.887	0.9997	468.2	8.6	0.885	0.9991	663.5
Pik	11.1	0.888	0.9968	741.8	15.5	0.893	0.9975	1036.5
SSC	10.3	0.874	0.9995	449.7	14.6	0.873	0.9992	633.7
Mean	9.1	0.88	0.9991	496.3	12.6	0.877	0.9990	689.1

Additional information

One study investigating the adsorption and desorption behaviour of the test substance to soil is available. This study was conducted as batch equilibrium method according to OECD Guideline 106.

The adsorption constants K_f(ads) of the substance calculated based on the Freundlich isotherms for the five test soils (sandy loam, silt loam, loam, loamy sand, clay loam) ranged from 6.1 to 11.1 L/kg. The respective K_oc(ads) values were in the range of 395.8 to 741.8 L/kg (mean 496.3 L/kg).

The desorption constants K_f(des) of the substance were significantly higher (up to 1.4 times) than the respective adsorption constants, indicating a strengthened binding of the substance once adsorbed to the soils.

According to Briggs (1973) classification for the estimation of mobility of crop protection agents in soil based on K_fand/or K_ocvalues, the substance can be classified as low mobile for both, adsorption and desorption.

There was no significant correlation between pH and adsorption for the investigated soils.

The test item was stable in the course of the study. The parental mass balance for the adsorption/desorption phase was > 90%. No major degradation product was observed.

 

 

References:

Briggs, G. G.: A simple relationship between soil adsorption of organic chemicals and their octanol/water partition coefficients; Proc. 7^thBritish Insecticide and Fungicide conference, Nottingham /, 1973