Registration Dossier

Environmental fate & pathways

Adsorption / desorption

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
adsorption / desorption: screening
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Principles of method if other than guideline:
The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).
GLP compliance:
no
Type:
Koc
Value:
3.715 L/kg
pH:
7
Remarks on result:
other: 20-25 °C
Type:
log Koc
Value:
0.57 dimensionless
pH:
7
Remarks on result:
other: 20-25 °C

The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

Validity criteria fulfilled:
not applicable
Conclusions:
The log Koc was 0.57 as calculated with an appropriate prediction method.
Endpoint:
adsorption / desorption, other
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:
1. SOFTWARE
ChemProp(TM) Main Module 6.5, Public OSIRIS Edition

2. MODEL (incl. version number)
Franco, Fu & Trapp (Partitioning, soil sorption coefficient, Koc), ionizable substances, acids and bases

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
See “Test material information”

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
See attached information on the model provided by the developer. Further information on the OECD criteria as outlined by the applicant is provided below under "Any other information of materials and methods incl. tables"

5. APPLICABILITY DOMAIN
See attached information and information as provided in "Any other information on results incl. tables".

6. ADEQUACY OF THE RESULT
See assessment of adequacy as outlined in the "Overall remarks, attachments" section.
Qualifier:
according to
Version / remarks:
REACH Guidance on QSARs R.6
Principles of method if other than guideline:
- Software tool(s) used including version: ChemProp v6.5
- Model(s) used: Franco, Fu & Trapp
Full reference and details of the used formulas can be found in:
1. Franco A, Fu W, Trapp S 2009. Influence of soil pH on the sorption of ionizable chemicals: Modeling advances. Environ. Toxicol. Chem. 28: 458-464.
2. Franco A, Trapp S 2008. Estimation of the soil-water partition coefficient normalized to organic carbon for ionizable organic chemicals. Environ. Toxicol. Chem. 27: 1995-2004.
- Model description: see field 'attached justification' and 'any other information on material and methods'
- Justification of QSAR prediction: see field 'Justification for type of information', 'Attached justification' and/or 'overall remarks'
GLP compliance:
no
Type of method:
other: calculation
Media:
soil
Details on test conditions:
BASIS FOR CALCULATION OF Koc:
- Estimation software: ChemProp v6.5, Franco and Trapp 2008 model for bases
- Log Kow: -2.3
- pKa: 11.3
- pH: 4, 7, 9
Type:
Koc
Value:
0.741 L/kg
pH:
7
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
log Koc
Value:
-0.13 dimensionless
pH:
7
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
Koc
Value:
0.738 L/kg
pH:
4
% Org. carbon:
5
Remarks on result:
other: based on eq.2 (acids)
Type:
log Koc
Value:
-0.132 dimensionless
pH:
4
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
Koc
Value:
0.761 L/kg
pH:
9
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)
Type:
log Koc
Value:
-0.118 dimensionless
pH:
9
% Org. carbon:
5
Remarks on result:
other: based on eq. 2 (acids)

For detailed information on the results please refer to the attached report.

Validity criteria fulfilled:
not applicable
Conclusions:
The log Koc was -0.13 at pH 7 as calculated with an appropriate prediction method.
Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
16 Nov 2016 - 19 Sep 2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Version / remarks:
2000
GLP compliance:
yes (incl. certificate)
Remarks:
Staatliches Gewerbeaufsichtsamt Hildesheim, Germany
Type of method:
batch equilibrium method
Media:
soil
Radiolabelling:
no
Test temperature:
20 °C ± 2 °C
Analytical monitoring:
yes
Remarks:
LC-MS/MS
Details on sampling:
- Concentrations for adsorption experiments: 0.2, 1, 2, 10, 20 mg/L
- Samples for adsortion experiment: The soil samples were conditioned as described under "Details on matrix". 1 volume-% of the stock solutions, related to the volume of the aqueous phase in the soil suspensions, was added to adjust the test concentrations. Afterwards, the samples were agitated for 0.5 h.
- Hydrolysis samples: Soils and 0.01 M CaCl2 were conditioned as described under "Details on matrix". Afterwards, the aqueous phase was separated by centrifugation and fortified with the test item. Samples were analyzed to determine hydrolysis of the test itemby analysing the concentration of Methyl-[3-trimethoxysilyl)propyl]carbamateby LC-MS/MS.
- Samples for desorption: The desorption behaviour of the test item was not investigated because no adsorption was observed.
- Samples for analysis: The soil suspensions were centrifuged after agitation at 3000 rpm to separate the phases, followed by analysing the concentration of Methyl-[3-(trimethoxysilyl)propyl]carbamate by LC-MS/MS. For analysis of the soil, the aqueous phase was decanted and the soil was extracted. Extracts were also analysed by LC-MS/MS.
- Sample storage before analysis: no storage
Matrix no.:
#1
Matrix type:
other: Rendzina
% Clay:
22.6
% Silt:
64.1
% Sand:
13.4
% Org. carbon:
3.72
pH:
7.1
CEC:
28.9 other: mval/100g
Matrix no.:
#2
Matrix type:
other: Dystric Cambisol
% Clay:
17
% Silt:
36.8
% Sand:
46.4
% Org. carbon:
3.01
pH:
5.5
CEC:
16.6 other: mval/100g
Matrix no.:
#3
Matrix type:
other: Orthic Luvizol
% Clay:
20.3
% Silt:
75.7
% Sand:
4.1
% Org. carbon:
1.31
pH:
6.7
CEC:
17.3 other: mval/100g
Matrix no.:
#4
Matrix type:
loam
% Clay:
25.2
% Silt:
42.3
% Sand:
32.6
% Org. carbon:
1.74
pH:
7.2
CEC:
22 other: mval/100g
Matrix no.:
#5
Matrix type:
sandy loam
% Clay:
10.2
% Silt:
31.1
% Sand:
58.7
% Org. carbon:
0.92
pH:
7.2
CEC:
10 other: mval/100g
Details on matrix:
COLLECTION AND STORAGE
- Standard eurosoils no. 2, 3 and 4 and standard LUFA soils 2.4 and 5M were used for the study.
- Origin: European Commission, Joint Research Centre, INSTITUTE FOR REFERENCE MATERIALS AND MEASUREMENTS IRMM, Geel, Belgium and LANDWIRTSCHAFTLICHE UNTERSUCHUNGS- UND FORSCHUNGSANSTALT LUFA SPEYER, Speyer, Germany
- Soil labels:
Eurosoil 2 (Rendzina)
Eurosoil 3 (Dystric Cambisol)
Eurosoil 4 (Orthic Luvizol)
LUFA 2.4 (loam)
LUFA 5M (sandy loam)
- Storage conditions: Eurosoils: Room temperature, in brown glass bottles, LUFA soils: Room temperature, in closed containers
- Soil preparation (e.g.: 2 mm sieved; air dried etc.): All soils were air-dried and sieved to a maximum particle size of 2 mm by the distributor.
- Conditioning: The soils were weighed into the test vessels and an appropriate volume of 0.01 M CaCl2-solution (1:1 soil/solution - 7.5 g soil and 7.5 mL 0.01 M CaCl2-solution) was added. After agitation overnight (12 h minimum), the samples were used for adsorption experiments.

PROPERTIES
- see matrix properties
Details on test conditions:
TEST CONDITIONS
- pH: between 5.5 and 7.2 (for details see field "any other information on results incl. tables")

TEST SYSTEM
- Type, size and further details on reaction vessel: 20 mL headspace vials (Tier 1), 50 mL disposable centrifugation tubes (Tier 3)
- Soil - CaCl2 solution ratio: 1:1
- Number of reaction vessels/concentration: 2
- Test performed in closed vessels due to significant volatility of test substance: no
- Method of preparation of test solution: CaCl2-solution was prepared in distilled water
- Are the residues from the adsorption phase used for desorption: no
- Other: Blank samples were prepared for all soils as described for the test item samples but without fortification with the test item. The samples were agitated as long as the samples with the longest agitation period (0.5 h).
Remarks:
Was not determined due to fast transformation of the substance.
Remarks:
Was not determined due to fast transformation of the substance.
Remarks on result:
other: No adsorption was observed
Remarks:
For details see "any other information on results incl. tables"
Remarks on result:
other: No adsorption was observed
Remarks:
For details see "any other information on results incl. tables"
Sample no.:
#1
Duration:
30 min
% Adsorption:
62
Remarks on result:
other: Eurosoil 2
Remarks:
20 mg/L
Sample no.:
#2
Duration:
30 min
% Adsorption:
62
Remarks on result:
other: Eurosoil 2
Remarks:
10 mg/L
Sample no.:
#3
Duration:
30 min
% Adsorption:
63
Remarks on result:
other: Eurosoil 2
Remarks:
2 mg/L
Sample no.:
#4
Duration:
30 min
% Adsorption:
63
Remarks on result:
other: Eurosoil 2
Remarks:
1 mg/L
Sample no.:
#5
Duration:
30 min
% Adsorption:
32
Remarks on result:
other: Eurosoil 2
Remarks:
0.2 mg/L
Sample no.:
#1
Duration:
30 min
% Adsorption:
52
Remarks on result:
other: Eurosoil 3
Remarks:
20 mg/L
Sample no.:
#2
Duration:
30 min
% Adsorption:
42
Remarks on result:
other: Eurosoil 3
Remarks:
10 mg/L
Sample no.:
#3
Duration:
30 min
% Adsorption:
40
Remarks on result:
other: Eurosoil 3
Remarks:
2 mg/L
Sample no.:
#4
Duration:
30 min
% Adsorption:
42
Remarks on result:
other: Eurosoil 3
Remarks:
1 mg/L
Sample no.:
#5
Duration:
30 min
% Adsorption:
43
Remarks on result:
other: Eurosoil 3
Remarks:
0.2 mg/L
Sample no.:
#1
Duration:
30 min
% Adsorption:
73
Remarks on result:
other: Eurosoil 4
Remarks:
20 mg/L
Sample no.:
#2
Duration:
30 min
% Adsorption:
67
Remarks on result:
other: Eurosoil 4
Remarks:
10 mg/L
Sample no.:
#3
Duration:
30 min
% Adsorption:
85
Remarks on result:
other: Eurosoil 4
Remarks:
2 mg/L
Sample no.:
#4
Duration:
30 min
% Adsorption:
74
Remarks on result:
other: Eurosoil 4
Remarks:
1 mg/L
Sample no.:
#5
Duration:
30 min
% Adsorption:
71
Remarks on result:
other: Eurosoil 4
Remarks:
0.2 mg/L
Sample no.:
#1
Duration:
30 min
% Adsorption:
73
Remarks on result:
other: LUFA 2.4
Remarks:
20 mg/L
Sample no.:
#2
Duration:
30 min
% Adsorption:
72
Remarks on result:
other: LUFA 2.4
Remarks:
10 mg/L
Sample no.:
#3
Duration:
30 min
% Adsorption:
69
Remarks on result:
other: LUFA 2.4
Remarks:
2 mg/L
Sample no.:
#4
Duration:
30 min
% Adsorption:
92
Remarks on result:
other: LUFA 2.4
Remarks:
1 mg/L
Sample no.:
#5
Duration:
30 min
% Adsorption:
64
Remarks on result:
other: LUFA 2.4
Remarks:
0.2 mg/L
Sample no.:
#1
Duration:
30 min
% Adsorption:
70
Remarks on result:
other: LUFA 5M
Remarks:
20 mg/L
Sample no.:
#2
Duration:
30 min
% Adsorption:
69
Remarks on result:
other: LUFA 5M
Remarks:
10 mg/L
Sample no.:
#3
Duration:
30 min
% Adsorption:
72
Remarks on result:
other: LUFA 5M
Remarks:
2 mg/L
Sample no.:
#4
Duration:
30 min
% Adsorption:
71
Remarks on result:
other: LUFA 5M
Remarks:
1 mg/L
Sample no.:
#5
Duration:
30 min
% Adsorption:
75
Remarks on result:
other: LUFA 5M
Remarks:
0.2 mg/L
Transformation products:
not specified
Details on results (Batch equilibrium method):
MAIN TEST: PERFORMANCE
- Test material stability during adsorption/desorption phase: hydrolytically unstable
- Experimental conditions maintained throughout the study: yes
- Anomalies or problems encountered (if yes): yes, see "any other information on material and methods incl. tables"

HYDROLYSIS EXPERIMENT (Tier 1 study)

Table 1: Hydrolysis Rate in Aqueous Sample (nominal concentration: 1000 µg test item/L, n=2).

 

Eurosoil 2

Eurosoil 3

Eurosoil 4

LUFA 2.4

LUFA 5M

Reaction rate constant k [1/s]

1.09 * 10-4

4.43 * 10-5

8.94 * 10-5

1.84 * 10-4

1.04 * 10-4

Hydrolysis half-life T1/2 [h]

1.8

4.3

2.2

1.0

1.9

ADSORPTION EXPERIMENT (Tier 3 study)

- As the test item stability in the test system is limited, no test guideline experiments to determine the kinetics of adsorption equilibrium have been conducted and the duration of the adsorption experiments was set to 30 min. For the same reason, the desorption isotherm was not determined.

- The mass balance was calculated from measured amounts of aqueous phase and soil extracts and was between 44 and 74% (mean of all concentrations) for all soils.

- No adsorption was observed for the test item in the experiments with all tested soils. At the end of the adsorption experiment, the measured amount of test item in soil was lower than expected based on the residue of the test item that was calculated to be in the remaining pore water. This is assumed to be due to further hydrolysis occurring during sample preparation. According ot the report determination of desorption data for this test item according to the guideline is not useful because no adsorption was observed. For this reason, no endpoints for desorption are presented in this report.

Table 2: pH values of the aqueous media.

 

Soils

 

Eurosoil 2

Eurosoil 3

Eurosoil 4

LUFA 2.4

LUFA 5M

0.01 M CaCl2

6.5

after soil contact

7.1

5.5

6.7

7.2

7.2

after addition of the test item

7.2

6.2

6.8

7.2

7.2

after desorption

7.2

6.1

6.7

7.2

7.2

Validity criteria fulfilled:
not applicable
Conclusions:
The adsorption potential of the substance was tested according to OECD guidance 106. The hydrolysis rate and a hydrolytic half-life were determined in soil-conditioned 0.01 M CaCl2 solution for each soil and spiked with the test item. Half-lives between 1 - 4.3 h were determined for the substance depending on the soil. The substance was not found to adsorb to soil.

Description of key information

Methyl-N- [3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4): no adsorption potential (OECD 106)

methyl-N-[3 (trihydroxysilyl)propyl]carbamate (silanol hydrolysis product): log Koc = 0.57 (QSAR, PFA, 2019)

Key value for chemical safety assessment

Koc at 20 °C:
3.715

Additional information

Methyl-N- [3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) decomposes fast in the environment, due to rapid hydrolysis in contact with water forming the corresponding hydrolysis products methyl-N-[3 (trihydroxysilyl)propyl]carbamate and methanol.

A study was conducted according to OECD 106 with the parent substance in order to identify its adsorption/desorption properties (2017). Five different soils were used for the experiments with pH values between 5.5 and 7.2. Soils with pH close to neutral were chosen since the substance is hydrolytically unstable and hydrolysis was expected to be slowest for neutral pH. A Tier 1 test (hydrolysis rate in aqueous samples) was conducted in order to check the stability of the substance in the soils. The hydrolysis half-life was between 1 and 4.3 h. Due to fast hydrolysis a Tier 2 test (determination of adsorption kinetics) was omitted and the study design of the Tier 3 (determination of adsorption isotherms) test was adjusted according to the opinion published by the scientific committee on plants on methods for the determination of the organic carbon adsorption coefficient (KOC) for a plant protection product active substance (SCP/KOC/002). The experiment was conducted with five concentrations ranging from 0.2 to 20 mg test item/L in order to determine the adsorption isotherms. The incubation time was adjusted to 0.5 h due to fast hydrolysis of the substance. The aqueous phase and the extracted solid phase were analyzed via LC-MS/MS after the adsorption experiment. No adsorption was determined and therefore no Koc values were calculated in the study.

Since the substance is hydrolytically unstable further information on the adsorption behavior of the silanol hydrolysis product was collected by two appropriate calculation methods.

In the first method the Koc was calculated with a prediction method developed especially for organosilicon compounds including N-containing substances (PFA, 2019). With this method a log Koc of 0.57 was calculated for the silanol hydrolysis product methyl-N-[3 (trihydroxysilyl)propyl]carbamate (neutral pH)

Considering the ionizing properties of the compound, the adsorption potential has been additionally calculated using Franco and Trapp ‘s expressions (2008) on estimation of the organic carbon-water partitioning coefficient of ionisable organic substances. The adsorption potential was calculated for pH 4, 7 and 9. The environmental relevant pKa of the hydrolysis product determined with SPARC was 11.3. The calculated log Koc of the hydrolysis product was -0.132 at pH 4, -0.13 at pH 7 and 0.118 at pH 9.

Both the experimental study for the parent substance and the QSAR calculations with the hydrolysis product reveal a negligible adsorption potential in soils and sediments.

Since the hydrolysis of the substance at pH 4, 5 and 9 was identified to be very fast it is assumed that under environmental conditions the hydrolysis product will be the dominant species present and therefore its log Koc values are considered more appropriate for the chemical safety assessment.