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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The Soil Adsorption Coefficient i.e Koc value of 4',5'-Dibromofluorescein was estimated using EPI suite  KOCWIN Program (v2.00) program as Koc 722800 L/kg(log Koc=5.8590)  by means of MCI method at 25 deg.C. This Koc value indicates that the substance 4',5'-Dibromofluorescein has very strong sorption to soil and sediment and therefore have negligible  migration potential to groundwater.

Key value for chemical safety assessment

Koc at 20 °C:
722 800

Additional information

Experimental and Predicted data of adsorption endpoint for the target chemical 4',5'-Dibromofluorescein (Cas no. 596-03-2) and its read across chemical were reviewed to summarize as follows:  

From predicted model EPI suite 2016 indicate that the soil adsorption coefficient (Koc) value of chemical 4',5'-Dibromofluorescein is estimated to be 722800 L/kg (log KOC = 5.8590), indicating that it is has very strong sorption to soil and sediment and therefore have negligible migration potential to groundwater.

Whereas from chemspider predicted database soil adsorption coefficient i.e Koc value of test substance 4',5'-Dibromofluorescein was estimated to be 18629.89 L/Kg i.e Log Koc= 4.2702 at pH 5.5 and 15748.58 L/Kg i.e Log Koc=4.1972 at pH 7.4

This Koc value indicates that the substance 4',5'-Dibromofluorescein has very strong sorption to soil and sediment and therefore have negligible migration potential to groundwater.

 And read across fluorescein (Cas no. 2321-07-5)experimental study from HSDB authorative database indicate that the adsorption coefficient (Koc) of substance fluorescein was found to be 260000 using a structure estimation method based on molecular connectivity indices. This Koc value suggests that fluorescein is expected to be immobile mobility in soil.

Other experimental study for read across Sodium Fluorescein (synonym Uranine)(Cas no. 518-47-8) (Bull. Environ. Contam. Toxicol. (1998) 61:426-432) investigated the dissipation and fate of phloxine B and uranine in water and sediment in the spill site. Distribution coefficients (Koc) of phloxine B and uranine were determined.It was observed that adsorption coefficients of uranine were higher in soil than in sediments although the organic carbon content of the sediment is higher than soil. Uranine was not detected in the sediment samples after 284 days. Uranine was less persistent compared to Phloxine B.

The adsorption coefficient (Koc) value of Uranine in soil was found to be 88.81 along with percentage organic carbon of 3.10%.

Whereas in other peer reviewed study for same read across i.e Cas no. 518-47-8 (Groundwater, Volume 29, Issue 3, May 1991, Pages 341–349) Inspection of the adsorption isotherm for fluorescein indicates that it demonstrated linearity at low concentrations with non linearity experienced at higher concentrations. The koc value of 120 cm3/g for fluorescein was obtained in the batch equilibrium studies. The Freundlich adsorption isotherm could not be estimated due to the discontinuous nature of the adsorption isotherm and background fluorescence observed at higher concentrations.

Similarly in other experimental study above mentioned read across indicate the adsorption coefficients of uranine were higher in soil than in sediments although the organic carbon content of the sediment is higher than soil. Uranine was not detected in the sediment samples after 284 days. Uranine was less persistent compared to Phloxine B.

The adsorption coefficient (Koc) value of Uranine in sediment was found to be 69.43 along with percentage organic carbon of 3.94 %.( Bull. Environ. Contam. Toxicol. (1998) 61:426-432)

Thus based on the above all studies it is concluded that the test substance 4',5'-Dibromofluorescein (Cas no. 596-03-2)have very strong sorption to soil/ sediment i.e immobile in soil compartment.

[LogKoc: 5.859]