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Environmental fate & pathways

Adsorption / desorption

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Description of key information

The adsorption coefficient of Modified Small Vinyl Ester was determined experimentally following the OECD Guideline no. 121 and in accordance with GLP. Estimation of the Adsorption Coefficient (Koc) on soil and on sewage sludge using High Performance Liquid Chromatography (HPLC) using soil-adsorption-reference data for the determination of the adsorption coefficient (Koc) of Modified Small Vinyl Ester. At neutral pH the minor constituent (monomaleic adduct of bisGMA, ca. 14.5%) has a logKoc smaller than 1.26. The main constituent (bisGMA, ca. 57%) has a logKoc of 4.16. At pH=2 constituents have logKoc's of 4.05 and 4.26, respectively. Using the experimental data for the main constituents, an average Koc was calculated to 14,600 (logKoc = 4.16) omitting the value for monomaleic adduct of bisGMA at neutral pH.

Key value for chemical safety assessment

Koc at 20 °C:
14 624

Additional information

The adsorption coefficient of Modified Small Vinyl Ester was determined experimentally following the OECD Guideline no. 121 and in accordance with GLP. Estimation of the Adsorption Coefficient (Koc) on soil and on sewage sludge using High Performance Liquid Chromatography (HPLC) using soil-adsorption-reference data for the determination of the adsorption coefficient (Koc) of Modified Small Vinyl Ester. The log Koc values at 35 °C of Modified Small Vinyl Ester were:

At neutral pH:

log Koc : ≤1.26 and 4.16 for major peaks (Koc = 18.2 and 14,454, respectively)

At pH 2:

log Koc : 4.05 and 4.26 for major peaks (Koc = 11,221 and 18,197, respectively)

At neutral pH monomaleic adduct of bisGMA is completely ionised. The relatively low log Koc indicates that monomaleic adduct of bisGMA will not bind tightly to soils and sediments at neutral pH.

The values larger than 4 indicate that bisGMA will bind tightly to soils and sediments at both pH's, and for monomaleic adduct of bisGMA at pH=2 at which pH it is non-ionised, and thus reduce overall exposure potential of Modified Small Vinyl Ester.

Monomaleic adduct of bisGMA amount approximately 14.5% of Modified Small Vinyl Ester. For the purpose of risk assessment the average of the Koc values for bisGMA and its monomaleic adduct (at pH=7) is used.