Octasodium 2,2'-[1,4-phenylenebis[imino(6-chloro-1,3,5-triazine-4,2-diyl)imino(1-hydroxy-3,6-disulphonatonaphthalene-2,8-diyl)azo]]bisnaphthalene-1,5-disulphonate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Remarks:

adsorption

Type of information:

(Q)SAR

Adequacy of study:

key study

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

Justification for type of information:

1. SOFTWARE
Individual model KOCWIN included in the Estimation Programs Interface (EPI) Suite.

2. MODEL (incl. version number)
KOCWIN v2.00 included in EPISuite v 4.11, 2000-2012.

3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
A SMILES notation was entered in the initial data entry screen. In the structure window, the molecular weight, structural formula and the structure of the input SMILES notation is shown.

4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Organic carbon partition coefficient, given as log Koc.
b. Dependent variable: KOCWIN estimates log Koc with two separate estimation methodologies:
(1) Estimation using first order Molecular Connecitivity Index (MCI),
(2) Estimation using log Kow (octanol-water partition coefficient)
c. Algorithm:
Log Koc according to MCI method is calculated using the formula:
log Koc = 0.5213 MCI + 0.60 + ΣPfN
(ΣPfN is the sum of all relevant correction factor coefficients multiplied by the number (N) of that factor in each chemical structure)
Log Koc according to the log Kow method is calculated using two formulas (depending on the polarity of the substance):
log Koc = 0.8679 log Kow - 0.0004 (Non-polar substances)
log Koc = 0.55313 log Kow + 0.9251 + ΣPfN (polar substances)

d. Descriptor values:
Log Kow method:
For estimation of log Koc according to log Kow method an experimentally determined log Kow of -1.57 was used (REACH&Colours Kft, 2013).

e. Applicability domain: The minimum and maximum values for molecular weight are the following:
Training Set Molecular Weights: 32.04-665.02 g/mol,
Validation Set Molecular Weights: 27.03-991.15 g/mol

f. Statistics for goodness-of-fit:

Statistical accuracy of MCI methodology for training and validation set:
i. Training without corrections:
Number: 69
R^2 correction coefficient: 0.967
Standard deviation (log Koc): 0.247
Average deviation (log Koc): 0.199

ii. Training with corrections:
Number: 447
R^2 correction coefficient: 0.900
Standard deviation (log Koc): 0.340
Average deviation (log Koc): 0.273

iii. Validation data set:
Number: 158
R^2 correction coefficient: 0.850
Standard deviation (log Koc): 0.583
Average deviation (log Koc): 0.459

Statistical accuracy of Log Koc methodology:
i. Training without corrections:
Number: 68
R^2 correction coefficient: 0.877
Standard deviation: 0.478
Average deviation: 0.371

ii. Training with corrections:
Number: 447
R^2 correction coefficient: 0.855
Standard deviation (log Koc): 0.396
Average deviation (log Koc): 0.307

iii. Validation data set:
Number: 150
R^2 correction coefficient: 0.778
Standard deviation (log Koc): 0.679
Average deviation (log Koc): 0.494

g. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. This characteristic is triggered by lipophilic character of substances but may be modified by certain molecular fragments that need to be considered by application of correction factors. The Log Koc is a physical inherent property used extensively to describe a chemical’s likeliness to adsorb to organic carbon.
h. The uncertainty of the prediction (OECD principle 4): Bayscript Magenta BB is highly complex and not all of the rules applied for the substance appear appropriate. Not all fragment descriptors are found by the program and counted correct by the number of occurrences. The fragment descriptor ‘Sulfonic acid (-S(=O)-OH)’ was counted only once by the program while the fragment occurred eight times in the molecule. This could especially have an effect on log Koc calculation using the MCI method as a high correction factor of 2.0 was used by this method for this fragment. Additionally the molecular weight of Bayscript Magenta BB is out of range of the training and validation set. Therefore an individual uncertainty for the investigated substance is available.

5. APPLICABILITY DOMAIN
a. Descriptor domains:
i. Molecular weights: With a molecular weight of 1774.2 g/mole the substance is out of the range of the training set (32 - 665 g/mol) as well as out of the range of the validation set (27 -– 991 g/mol).
ii. Structural fragment domain: Regarding the structure of Reactive Red 141 most of the fragment descriptors found by the program are complete and listed in Appendix D (KOCWIN Fragment and Correction Factor descriptors) except the fragment descriptor ‘Sulfonic acid (-S(=O)-OH)’. Additionally the fragment ‘Triazine ring’ was not included into calculation by the program and was added manually for calculation. For estimation of log Koc according to log Kow method the log Kow of -1.57 (experimentally determined, REACH&Colours Kft) was used.
iii. Mechanism domain: No information available.
iv. Metabolic domain: Not relevant.
b. Structural analogues: No information available.
i. Considerations on structural analogues: No information available.

6: UNCERTAINTY OF THE PREDICTION
Reactive Red 141 is highly complex and not all of the rules applied for the substance appear appropriate. Not all fragment descriptors are found by the program and counted correct by the number of occurrences. The fragment descriptor ‘Sulfonic acid (-S(=O)-OH)’ was counted only once by the program while the fragment occurred eight times in the molecule. This could especially have an effect on log Koc calculation using the MCI method as a high correction factor of 2.0 was used by this method for this fragment. Additionally the molecular weight of Reactive Red 141 is out of range of the training and validation set. Therefore an individual uncertainty for the investigated substance is available.

7. ADEQUACY OF THE RESULT
a. Regulatory purpose: The data may be used under any regulatory purpose.
b. Approach for regulatory interpretation of the model result: If no experimental data are available, the estimated value may be used to fill data gaps needed for hazard and risk assessment, classification and labelling and PBT / vPvB assessment. Further the value is used for other calculations.
c. Outcome: Under environmental relevant pHs, Reactive Red 141 exists predominantly in the dissociated form. At pH 4 to 9, the substance will be deprotonated resulting in the corresponding anion. As anionic substances in particular generally do not adsorb strongly, an adsorption potential of the dissociated form of Bayscript Magenta BB is not expected. Estimation Program Interface (EPI) Suite indicates that the Koc of this structure may be sensitive to pH. However QSAR estimations on dissociation constant showed that sulphonic acid groups of Reactive Red 141 are already dissociated at pH ≥ 2. Therefore, the Koc may not be vary significantly at environmental relevant pH (pH 4-9).
The results of log Kow method and MCI method differ significantly. It can be assumed that high log Koc values calculated by MCI method are caused by estimated fragment descriptors that are not found by the program. As Reactive Red 141 exhibits a low
log Kow value of -1.57 (experimental determined, REACH&Colours Kft, 2013) and is highly water soluble (411 g/L, experimental determined, REACH&Colours Kft, 2013) the substance is expected to have negligible sorption to soil and sediment. Therefore,
the prediction of organic carbon partition coefficient using log Kow method yields a useful result for further evaluation.
d. Conclusion: Under environmental relevant pH, Reactive Red 141 exists predominantly in the dissociated form. At pH 4 to 9, the sulphonic acid groups of the substance will be deprotonated resulting in the corresponding anion. As anionic substances in particular generally do not adsorb strongly, an adsorption potential of the dissociated form of Reactive Red 141 is not expected. Based on the experimental determined log Kow value of -1.57 and the water solubility of 411 g/L Reactive Red 141 is expected to show negligible sorption to soil and sediment. Therefore the result of the log Kow method is considered as useful for regulatory purposes.

Qualifier:

according to guideline

Guideline:

other: REACH guidance QSARs R6, May/July 2008

Principles of method if other than guideline:

Estimation Program Interface EPI-Suite version 4.11: KOCWIN (v2.00) for the estimation of the organic carbon-normalized sorption coefficient for soil and sediment (Koc).
The Estimation Program Interface was developed by the US Environmental Agency's Office of Pollution Prevention and Toxics, and Syracuse Research Corporation (SRC). © 2000 - 2012 U.S. Environmental Protection Agency for EPI SuiteTM (Published online in November 2012).

GLP compliance:

no

Type of method:

other: Estimation

Media:

soil

Radiolabelling:

no

Type:

log Koc

Value:

0.961 dimensionless

Remarks on result:

other: calculation (logKow method); calculated values based on ambient temperature and neutral pH conditions

Type:

log Koc

Value:

20.23 dimensionless

Remarks on result:

other: calculation (MCI method); calculated values based on ambient temperature and neutral pH conditions

Phase system:

other: Koc

Type:

other: Koc

Value:

9.15 L/kg

Remarks on result:

other: calculation (logKow method); calculated values based on ambient temperature and neutral pH conditions

Phase system:

other: Koc

Type:

other: Koc

Value:

1 690 000 000 000 000 000 000 L/kg

Remarks on result:

other: calculation (MCI method); calculated values based on ambient temperature and neutral pH conditions

Validity of the model:

1. Defined Endpoint: Organic carbon partition coefficient, given as logarithmic Koc and Koc

2. Unambigous algorithm: The molecule is first classified as a polar substance. Based on structure of the molecule, the following fragments were applied:

MCI method and log Kow method: Nitrogen to non-fused aromatic ring, Azo (-N-N-), Triazine ring, Sulfonic acid (-S(=O)-OH), Aromatic hydroxy (aromatic-OH)

Not all fragment descriptors are found by the program and counted correct by the number of occurrences. The fragment descriptor ‘Sulfonic acid (-S(=O)-OH)’ was counted only once by the program while the fragment occurred eight times in the molecule. This could especially have an effect on log Koc calculation using the MCI method as a high correction factor of 2.0 was used by this method for this fragment.

For estimation of logKoc according to the logKow method the estimated logKow of -1.57 as calculated by the program was used.

3. Applicable domain: With a molecular weight of 1774.2 g/mol the substance is out of the range of the training set (32 - 665 g/mol) as well as out of the validation set (27 - 991 g/mol).

Regarding the structure of Reactive Red 141 most of the fragment descriptors found by the program are complete and listed in Appendix D (KOCWIN Fragment and Correction Factor descriptors) except the fragment descriptor ‘Sulfonic acid (-S(=O)-OH)’. Additionally the fragment ‘Triazine ring’ was not included into calculation by the program and was added manually for calculation.

4a. Statistical characteristics (MCI method): N training set without corrections = 69; N training set with correction = 447; N validation set = 158; Correction coefficient of the total training set without corrections r² = 0.967; Correlation coefficient of the total training set with corrections r² = 0.900; Correlation coefficient of the total validation set r² = 0.850.

4b. Statistical characteristics (Kow method): N training set without corrections = 68; N training set with correction = 447; N validation set = 150; Correction coefficient of the total training set without corrections r² = 0.877; Correlation coefficient of the total training set with corrections r² = 0.855; Correlation coefficient of the total validation set r² = 0.778.

5. Mechanistic interpretation: Log Koc is estimated based on the likeliness of a substance for sorption to surfaces of soil/sediment particles. The log Koc is a physical inherent property used extensively to describe a chemical's likeliness to adsorb to organic carbon.

6. Adequacy of prediction: The result for Reactive Red 141 falls within the applicability domain described above and the estimation rules applied for the substance appears appropriate.

Validity criteria fulfilled:

not applicable

Conclusions:

The QSAR determination of the carbon partition coefficient for Reactive Red 141 using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.11 revealed values of 9.15 L/kg (logKow method) and 1.69 x 10E20 L/kg (MCI method) for the unaffected molecule of Reactive Red 141 as any decomposition (e.g. hydrolysis) is not taken into account by the program.

Executive summary:

The organic carbon partition coefficient (Koc) for Reactive Red 141 was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The Koc was estimated to be 9.15 L/kg (logKow method), and 1.69 x 10²⁰ L/kg (MCI method). The results relate to the unaffected molecule of Reactive Red 141 as any decomposition (e.g. hydrolysis) is not taken into account by the program.

Under environmental relevant pHs, Reactive Red 141 exists predominantly in the dissociated form. At pH 4 to 9, the substance will be deprotonated resulting in the

corresponding anion. As anionic substances in particular generally do not adsorb strongly, an adsorption potential of the dissociated form of Reactive Red 141 is

not expected. The results of log Kow method and MCI method differ significantly. It can be assumed that high log Koc values calculated by MCI method are caused by estimated fragment descriptors that are not found by the program. As Reactive Red 141 exhibits a low log Kow value of -1.57 (experimental determined, REACH&Colours Kft, 2013) and is highly water soluble (411 g/L, experimental determined, REACH&Colours Kft, 2013) the substance is expected to have negligible sorption to soil and sediment. Therefore, the prediction of organic carbon partition coefficient using log Kow method yields a useful result for further evaluation.

Description of key information

The organic carbon partition coefficient (Koc) for Reactive Red 141 was predicted using the QSAR calculation of the Estimation Program Interface (EPI) Suite v 4.11. The Koc was estimated to be 9.15 L/kg (logKow method), and 1.69 x 10²⁰L/kg (MCI method). The results relate to the unaffected molecule of Reactive Red 141 as any decomposition (e.g. hydrolysis) is not taken into account by the program.

Key value for chemical safety assessment

Koc at 20 °C:

9.15

Additional information

Under environmental relevant pH, Reactive Red 141 exists predominantly in the dissociated form. At pH 4 to 9, the sulphonic acid groups of the substance will be deprotonated resulting in the corresponding anion. As anionic substances in particular generally do not adsorb strongly, an adsorption potential of the dissociated form of Reactive Red 141 is not expected. Based on the experimental determined log Kow value of -1.57 and the water solubility of 411 g/L Reactive Red 141 is expected to show negligible sorption to soil and sediment. Therefore the result of the log Kow method is considered as useful for regulatory purposes.

[LogKoc: 0.961]