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Adsorption / desorption

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Description of key information

The adsorption coefficient of the substance could not be determined by the batch equilibrium method conducted in accordance with OECD Guideline 106.  Therefore, the key value was the adsorption coefficient of tetrapropenyl succinic anhydride, by read-across based on a grouping of substances (category approach).  The adsorption coefficient for tetrapropenyl succinic anhydride was determined on activated sludge by the batch equilibrium method in accordance with OECD Guideline 106.

Key value for chemical safety assessment

Koc at 20 °C:
825

Additional information

A study was initiated to determine the adsorption of the substancebut was terminated due to the low solubility of the substance.  The highest test concentration achievable was 1 mg Carbon/L; this concentration was near the quantitation limit for total organic carbon, and the study could not be conducted. Therefore, the key value for the adsorption coefficient of the substance is the experimentally-determined value for tetrapropenyl succinic anhydride, by read-across based on a grouping of substances (category approach).

 

The adsorption coefficient of tetrapropenyl succinic anhydride was determined as a function of the organic carbon content of the activated sludge. Activated sludge was selected for testing and was characterized for percent organic carbon. The percent adsorption, the adsorption coefficient (Kd) and the adsorption coefficient as a function of organic carbon (KOC) were determined from adsorption experiments. The percent desorption and the desorption coefficient (Kdes) were determined from the desorption kinetic experiments. Analysis of the test samples was performed by total organic carbon (TOC) analysis due to the rapid hydrolysis of the parent compound. The study was performed following the laboratory protocol entitled “TPSA – Determining the Adsorption Coefficient (KOC) Following OECD Guideline 106” and was conducted to meet the requirements specified in OECD Guideline No. 106.

The adsorption of tetrapropenyl succinic anhydride was evaluated using activated sludge at 20 ± 2°C. The Kd, and KOCand values for the test substance were determined at a sludge-to-solution ratio of 1:400 using data through 6 hours. The initial concentration of the test substance in the aqueous phase was 6.4 mg/L. The Kd and KOCvalues indicate that the test substance is moderately mobile (Koc<1000) and what adsorption there is, most likely is reversible considering the desorption values. The Koc for tetrapropenyl succinic anhydride was reported as Koc= 825 L/kg, or log Koc= 2.916, and were selected as the key values by read-across based on a grouping of substances (category approach).

A category approach is used for the hazard assessment of several endpoints. The hypothesis for the category of C8-12 Alkenyl Succinic Anhydrides is that data can be read-across among members of the category, because the properties and behaviours of category members are similar, based on common functional groups, similar breakdown products, and demonstration of a constant pattern associating the potency of properties with the various carbon chain lengths. Functional groups include a dihydro-2,5-furandione cyclic anhydride ring, a carbon chain of length 8 -12 carbons, and a single carbon-carbon double-bond within the carbon chain. The primary functional group associated with toxicity is the succinic anhydride moiety, which is quickly hydrolysed to form a butanedioic acid. A constant pattern may also be displayed in acute toxicity, dermal irritancy and biodegradation, with the lowest carbon chain length (C8) displaying the highest activity. Irritation, toxicity and degradation potential diminish with increasing carbon chain length. Read-across among the category members is substantiated by the common behaviour in physico-chemical and toxicity behaviours, as provided in the Chemical Category Report Format (CCRF) attached to the IUCLID file. It is adequate to fulfil the information requirements of Annex IX, to be the basis for classification and labelling decisions, and for risk assessment.

[LogKoc: 2.916]