Reaction mass of 5-[[4-[benzylmethylamino]phenyl]azo]-1,4-dimethyl-1H-1,2,4-triazolium methyl sulphate and 3-[[4-[benzylmethylamino]phenyl]azo]-1,4-dimethyl-1H-1,2,4-triazolium methyl sulphate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption: screening

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

weight of evidence

Study period:

This study was conducted between 08 November 2017 and 26 November 2017

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, and documentation / justification is limited

Justification for type of information:

Adsorption Coefficient
Testing was not carried out using Method 121 of the OECD Guidelines for Testing of Chemicals for the following reasons:

• The test item is a salt. The HPLC method is not applicable to substances such as this.

• The use of computer-based estimation programs and/or Quantitative Structure Activity relationships (QSAR’s) for materials of this nature are also considered invalid since most of these methods are based on estimations of Log Pow, itself prone to error due to the effects of ionic charge. Prediction methods are likely to be subject to serious error since they do not take into account the salted nature of the test item. The Log Pow result has been determined, however this is still a less than value due to the low determined results within the organic samples. Although correction factors can be applied, it has been shown that QSAR models can significantly under estimate the adsorption coefficient of ionic substances.

• Computer modelling software estimations (KOCWIN) produced the following data:
o Log Koc from structure = 1.68 x 104 L/kg and 7.98 x 103 L/kg (constituents 1 and 2 respectively)
o Log Koc from predicted Kow values = 2.60 L/kg and 14.5 L/kg (constituents 1 and 2 respectively)

Predicted values should be used with extreme caution, due to the above mentioned issues with the predictions.

Therefore, it has been considered that in this particular case, the adsorption coefficient end point is essentially meaningless and cannot be assessed.

Qualifier:

no guideline required

Principles of method if other than guideline:

No guideline required

Remarks on result:

not determinable

Description of key information

Determination of adsorption coefficient for Basic Red 046 Methyl Sulfate was considered to be not technically feasible, as HPLC method is not applicable for substances that are salt in nature. Hence, the adsorption coefficient was estimated using computer simulations (KOCWIN), which are presented below:

o       Log Koc from structure = 1.68 x 104 L/kg and 7.98 x 103 L/kg (constituents 1 and 2 respectively)

o       Log Koc from predicted Kow values = 2.60 L/kg and 14.5 L/kg (constituents 1 and 2 respectively)

The adsorption coefficient is required to estimate PNECs for sediment and soil when using the equilibrium partitioning method. Hence, to have a single value for adsorption coefficient, an estimation was carried out using KOCWIN v2.00 available in EPISUITE 4.10. The experimentally determined Log Kow = -1.86 for BASIC RED 046 METHOSLFATE was used for this purpose. The estimated Koc was 3.137 L/kg while the corrected log Koc was 0.4965.

Key value for chemical safety assessment

Koc at 20 °C:

3.137

Additional information

[LogKoc: 0.4965]