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Environmental fate & pathways

Hydrolysis

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Description of key information

In accordance with REACH Annex VIII column 2, the study does not need to be conducted if the substance is readily biodegradable or highly insoluble in water.
The following statement was included in a physico-chemical properties study by Walker & White (2010) concerning the feasibility of a hydrolysis study on dibutyltin methyl maleate:
“No determination was performed according to Method C7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008, for the following reason:
• During preliminary investigations for the water solubility test it was concluded that the test item hydrolysed fully within 30 minutes of contact with water. Substances which hydrolyse rapidly in contact with water are not suitable for determination using Method C7.”
In the water solubility test, the insoluble test item sat at the sides of the flask and quickly changed from an almost colourless liquid to a greasy white precipitate. The test item therefore hydrolyses immediately on contact with water to an insoluble solid. All dibutyltin compounds degrade into dibutyltin and the appropriate ligand, the white solid observed in the test is probably DBTO, which is known to be insoluble.
The following study was provided in support of omitting the test.
Yoder, R. (2003) Electrospray Ionization Mass Spectrometric Study of Dioctyltin Compounds in Solution.
Electrospray ionization mass spectrometry (ESI/MS) was used to determine whether dioctyltin compounds in water behave like dibutyltin compounds and form oxides relatively quickly The results of the test confirmed this theory. During the study, the test solutions were analysed immediately after the addition of test item, the analyses provided an indication of the speed of hydrolysis. In all samples hydrolysis products were observed under very short times. In particular, at 125 ng/ml (as Sn), almost the entire parent compound has converted to the oxide in less than 10 minutes (estimated).

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Additional information

Yoder (2003) was provided in support of omitting testing for this endpoint. The study was performed to a good scientific standard with a good level of reporting and was accordingly assigneed a reliability score of 2. The study demonstrated that hydrolysis is extremely rapid. The study was provided for information purposes only, the purpose of the study was to determine experimentally whether dioctyltins behave hydrolytically similarly to dibutyltin compounds.