Reaction mass of bis[3-[[4-[benzylmethylamino]phenyl]azo]-1,4-dimethyl-1H-1,2,4-triazolium] tetrachlorozincate(2-) and bis[5-[[4-[benzylmethylamino]phenyl]azo]-1,4-dimethyl-1H-1,2,4-triazolium] tetrachlorozincate(2-)

Adsorption / desorption

Description of key information

Determination of an adsorption coefficient 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 was used for this purpose. The estimated Koc was 3.137 L/kg while the corrected log Koc was 0.4965. As the CAS no. of the target substance (ZnCl4 salt) is not available within EPISuite, the CAS no. of the structural analogue substance was used. The dye component (cation) is the same structure for both salt types.

Key value for chemical safety assessment

Koc at 20 °C:

3.137