Reaction mass of Sodiumbis[1-[(2-hydroxy-5-nitrophenyl)azo]-2-naphtholato(2-)]chromate(1-) and Sodium [1-[(2-hydroxy-4-nitrophenyl)azo]-2-naphtholato(2-)][1-[(2-hydroxy-5-nitrophenyl)azo]-2-naphtholato(2-)]chromate(1-) and Sodiumbis[1-[(2-hydroxy-4-nitrophenyl)azo]-2-naphtholato(2-)]chromate(1-)

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

(Q)SAR

Adequacy of study:

supporting study

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

Remarks:

The QSAR was performed with the respective protonated salt(s) of the constituents, as the substance is ionic. As the position of the nitro-group has no influence on the estimated Koc-value, only the result of 1-[(2-hydroxy-4-nitrophenyl)azo]-2-naphtholato(2-) is presented. The estimated Koc-value was corrected twice (exceeded by 1) for the presence of aromatic hydroxy groups. Consequently, the estimate may be less accurate as this substance did not fall entirely into the applicability domain of the QSAR.

Justification for type of information:

- QMRF: see 'Overall remarks, attachments'.
- QPRF: see 'Executive summary'.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Calculation using KOCWIN (v2.00) Molecular Connectivity Index (MCI)

GLP compliance:

no

Type of method:

other: QSAR estimation: KOCWIN v2.00: Koc estimate from MCI

Specific details on test material used for the study:

- SMILES Code: c3c2c(ccc3)c(N=Nc1ccc(N(=O)(=O))cc1O)c(O)cc2

Test temperature:

25 °C

Type:

Koc

Value:

108 400 L/kg

Temp.:

25 °C

Type:

log Koc

Value:

5.035 dimensionless

Temp.:

25 °C

Koc Estimate from MCI:

First Order Molecular Connectivity Index	11.059
Non-Corrected Log Koc(0.5213 MCI + 0.60)	6.3646
Fragment Correction(s):
1 Nitro (-NO2)	-0.4889
1 Azo (-N=N-)	-0.6475
2 Aromatic Hydroxy (aromatic-OH)	-0.1932
Corrected Log Koc	5.0350
Estimated Koc	1.084E+005 L/kg

Executive summary:

QPRF: KOCWIN v2.00 (MCI methodology) (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 within range (309.28 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):  

Training set: Molecular weights	Training set	Validation set
Minimum	32.04	73.14
Maximum	665.02	504.12
Average	224.4	277.8
Assessment of molecular weight	Molecular weight within range of training set

Appendix D. MCI & Log Kow Correction Factors for 447 Compound Training Set

Correction Factor Descriptor	Coefficient for Molecular Connectivity Index (MCI) Regression Methodology		Occurrence		No. of instances of each bond found for the current substance
	(new model)	Remark	(number of compounds	(max. per structure)
Nitro (-NO2)	-0.488879	(a)	43	2	1
Azo (-N=N-)	-0.647525		3	1	1
Aromatic Hydroxy (aromatic-OH)	-0.09661		27	1	2

(a) Counted up to twice per structure, regardless of number of occurrences.

Description of key information

Based on the Kow-value of 1.3 - 1.9, adsorption of the substance is not expected. For 1-[(2-hydroxy-4-nitrophenyl)azo]-2-naphtholato(2-), the Koc value was calculated to be 1.084E+005 L/kg (log Koc = 5.04) when based on the MCI method. The log Kow method was not included, as the KOWWIN method overestimates the Kow of pigments (Chapter R.11, June 2017). Based on a log Koc >3, adsorption of the salt may be expected.

Key value for chemical safety assessment

Koc at 20 °C:

108 000

Additional information

QSAR-disclaimer:

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

For the assessment of 1-[(2-hydroxy-4-nitrophenyl)azo]-2-naphtholato(2-), a relevant protonated moeity of the salt, (Q)SAR results were used for adsorption / desorption. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be not entirely adequately fulfilled. However, the results do provide an indication on the potential of the moeities to adsorb.