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Adsorption / desorption

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Endpoint:
adsorption / desorption, other
Remarks:
adsorption, QSAR
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method, but substance not within applicability domain of model
Justification for type of information:
QSAR prediction
Principles of method if other than guideline:
KOCWIN (v2.00): estimation using estimated or experimentally derived log Kow
GLP compliance:
no
Type of method:
other: QSAR estimation: KOCWIN v2.00: Koc estimate from log Kow
Test temperature:
25 °C
Computational methods:
- Other: log Kow used for estimation: XXX (estimated by KOCWIN / experimental database of KOCWIN / experimental value, reference)
Type:
log Koc
Value:
12.1
Temp.:
25 °C
Remarks on result:
other: The substance is not within the applicability domain of the model.

Koc Estimate from MCI:

---------------------

First Order Molecular Connectivity Index ........... : 29.444

Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 15.9492

Fragment Correction(s):

2  Nitrogen to non-fused aromatic ring ... : -1.0450

12  Nitrogen to Carbon (aliphatic) (-N-C).. : -2.5528

1  Triazine ring ....................... : -0.2257

Corrected Log Koc .................................. : 12.1258

 

Estimated Koc: 1e+010 L/kg  <===========

Executive summary:

QPRF: KOCWIN v2.00 (18 Nov. 2013)

 

1.

Substance

See “Test material identity”

2.

General information

 

2.1

Date of QPRF

See “Data Source (Reference)”

2.2

QPRF author and contact details

See “Data Source (Reference)”

3.

Prediction

3.1

Endpoint
(OECD Principle 1)

Endpoint

Adsorption to solid phase of soils etc.

Dependent variable

Organic carbon normalised adsorption coefficient (Koc)

3.2

Algorithm
(OECD Principle 2)

Model or submodel name

KOCWIN

Model version

v. 2.00

Reference to QMRF

QMRF: Estimation of Soil Adsorption Coefficient using KOCWIN v2.00 (EPI Suite v4.11): Estimation using log Kow

Predicted value (model result)

See “Results and discussion”

Input for prediction

- Chemical structure via CAS number or SMILES

- log Kow (for log Kow method; optional)

Descriptor values

- Chemical structure

- Correction factors

3.3

Applicability domain
(OECD principle 3)

Domains:

1) Molecular weight
(range of test data set: 32.04 to 665.02 g/mol; On-Line KOCWIN User’s Guide, Ch. 6.2.4 Domain)

Substance not within range (886.42 g/mol)

2) log Kow (range of test data set: -2.11 to 8.12; On-Line KOCWIN User’s Guide, Appendices E & F)

Substance not within range (16.33)

3) Correction factors: Number of instances of the identified correction factor does not exceed the maximum number as listed in Appendix D (On-Line KOCWIN User’s Guide)

Not fulfilled.

3.4

The uncertainty of the prediction
(OECD principle 4)

Nonpolar compounds: n = 68; r2=0.478, average dev. = 0.371

Polar compounds: n = 447, r²=0.855, std. dev. = 0.396, average dev. = 0.307

3.5

The chemical mechanisms according to the model underpinning the predicted result
(OECD principle 5)

Adsorption is caused by temporary (reversible) or permanent bonding between the substance and a surface (e.g. due to van der Waals interactions, hydrogen bonding to hydroxyl groups, ionic interactions, covalent bonding, etc.). The organic carbon normalized adsorption coefficient (Koc) is the ratio of a substance concentration sorbed in the organic matter component of soil or sediment to that in the aqueous phase at equilibrium.

Estimation using log Kow: The model is based on the high correlation of log Kow and the adsorption potential.

 

References

- US EPA (2012). On-Line KOCWIN User’s Guide.

- Meylan, W., P.H. Howard and R.S. Boethling. 1992. Molecular topology/fragment contribution method for predicting soil sorption coefficients. Environ. Sci. Technol. 26: 1560-1567.

 

 

Assessment of estimation domain (molecular weight, fragments, correction factors):

 

  Molecular weight (g/mol)   log Kow
Minimum Maximum Average   Minimum Maximum
Training set 32.04 665.02 224.4   -2.11 8.12
Validation set 73.14 504.12 277.8   -5.98 8.68
Assessment of molecular weight Molecular weight outside of range of training and validation set. Therefore, the estimate may be less accurate.
 
             
Assessment of log Kow (only relevant for log Kow method) Log Kow outside of range of training and validation set. Therefore, the estimate may be less accurate.
             
Appendix D. MCI & Log Kow Correction Factors for 447 Compound Training Set    
Correction Factor Descriptor Coefficient for Molecular Connectivity Index (MCI) Regression Methodology Coefficient for log Kow Regression Methodology Occurrence No. of instances
of each bond
found for the
current substance
(new model)  Remark (number of compounds (max per structure)  
Nitrogen to non-fused aromatic ring  -0.52251 (a) -0.021606 154 2 2
Nitrogen to Carbon (aliphatic) (-N-C) -0.21273 c -0.021787 133 5 12
Triazine ring  -0.225664   -0.123923 18 1 1

 

Endpoint:
adsorption / desorption, other
Remarks:
adsorption, QSAR
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Accepted calculation method, but substance not within applicability domain of model
Justification for type of information:
QSAR prediction
Principles of method if other than guideline:
KOCWIN (v2.00): estimation using first-order Molecular Connectivity Index (MCI)
GLP compliance:
no
Type of method:
other: QSAR estimation: KOCWIN v2.00: Koc estimate from MCI
Test temperature:
25 °C
Type:
log Koc
Value:
9.5
Temp.:
25 °C
Remarks on result:
other: The substance is not within the applicability domain of the model.

Koc Estimate from Log Kow:

-------------------------

Log Kow (Kowwin estimate) ......................... : 16.33

Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 9.9577

Fragment Correction(s):

2  Nitrogen to non-fused aromatic ring ... : -0.0432

12  Nitrogen to Carbon (aliphatic) (-N-C).. : -0.2614

1  Triazine ring ....................... : -0.1239

Corrected Log Koc .................................. : 9.5291

 

Estimated Koc: 3.382e+009 L/kg  <===========

Executive summary:

QPRF: KOCWIN v2.00 (18 Nov. 2013)

 

1.

Substance

See “Test material identity”

2.

General information

 

2.1

Date of QPRF

See “Data Source (Reference)”

2.2

QPRF author and contact details

See “Data Source (Reference)”

3.

Prediction

3.1

Endpoint
(OECD Principle 1)

Endpoint

Adsorption to solid phase of soils etc.

Dependent variable

Organic carbon normalised adsorption coefficient (Koc)

3.2

Algorithm
(OECD Principle 2)

Model or submodel name

KOCWIN

Model version

v. 2.00

Reference to QMRF

QMRF: Estimation of Soil Adsorption Coefficient using KOCWIN v2.00 (EPI Suite v4.11): MCI methodology

Predicted value (model result)

See “Results and discussion”

Input for prediction

- Chemical structure via CAS number or SMILES

Descriptor values

- MCI (first order molecular connectivity index)

- Correction factors

3.3

Applicability domain
(OECD principle 3)

Domains:

1) Molecular weight
(range of test data set: 32.04 to 665.02 g/mol; On-Line KOCWIN User’s Guide, Ch. 6.2.4 Domain)

Substance not within range (886 g/mol)

2) Correction factors: Number of instances of the identified correction factor does not exceed the maximum number as listed in Appendix D (On-Line KOCWIN User’s Guide)

Not fulfilled.

3.4

The uncertainty of the prediction
(OECD principle 4)

Statistical accuracy for training dataset:

n = 516, r² = 0.916, std. dev. = 0.330, average dev. = 0.263

3.5

The chemical mechanisms according to the model underpinning the predicted result
(OECD principle 5)

Adsorption is caused by temporary (reversible) or permanent bonding between the substance and a surface (e.g. due to van der Waals interactions, hydrogen bonding to hydroxyl groups, ionic interactions, covalent bonding, etc.). The organic carbon normalized adsorption coefficient (Koc) is the ratio of a substance concentration sorbed in the organic matter component of soil or sediment to that in the aqueous phase at equilibrium.

MCI methodology: The first-order molecular connectivity index is a measure to describe a variety of properties of chemicals. According to Sabljic (1984; cited in Meylan et al., 1992), the soil sorption potential is highly correlated with the first order MCI. Therefore, it has been used to derive the adsorption coefficient.

 

References

- US EPA (2012). On-Line KOCWIN User’s Guide.

- Meylan, W., P.H. Howard and R.S. Boethling. 1992. Molecular topology/fragment contribution method for predicting soil sorption coefficients. Environ. Sci. Technol. 26: 1560-1567.

 

 

Assessment of estimation domain (molecular weight, fragments, correction factors):

 

  Molecular weight (g/mol)   log Kow
Minimum Maximum Average   Minimum Maximum
Training set 32.04 665.02 224.4   -2.11 8.12
Validation set 73.14 504.12 277.8   -5.98 8.68
Assessment of molecular weight Molecular weight outside of range of training and validation set. Therefore, the estimate may be less accurate.
 
             
Assessment of log Kow (only relevant for log Kow method) Log Kow outside of range of training and validation set. Therefore, the estimate may be less accurate.
             
Appendix D. MCI & Log Kow Correction Factors for 447 Compound Training Set    
Correction Factor Descriptor Coefficient for Molecular Connectivity Index (MCI) Regression Methodology Coefficient for log Kow Regression Methodology Occurrence No. of instances
of each bond
found for the
current substance
(new model)  Remark (number of compounds (max per structure)  
Nitrogen to non-fused aromatic ring  -0.52251 (a) -0.021606 154 2 2
Nitrogen to Carbon (aliphatic) (-N-C) -0.21273 c -0.021787 133 5 12
Triazine ring  -0.225664   -0.123923 18 1 1

 

Description of key information

Adsorption to the solid soil phase is expected.

Key value for chemical safety assessment

Additional information

The log Koc for the smallest component of the UVCB substance was calculated to be >> 5 using EPI Win. A log Koc of that value indicates that the test substance binds to soils and sediments. Although the compound was not inside the applicability domain of neither the MCI nor the logKow methodology the results seems to be reliable. Adsorption to the solid soil phase is expected.