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Environmental fate & pathways

Hydrolysis

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Formaldehyde release of EUF in aqueous solution was investigated for a 1%(v/v)solution at 20°C and pH-values of 7.2, 9.2, and 4.0 in H2O/DMSO-D6 (90/10) using 13C-NMR spectroscopy. The investigation follows the OECD Guideline 111, which was modified slightly due to technical reasons. The reaction rate of hydrolysis was determined via measurement of the formaldehyde being released. It was found that at pH 7.2 and 9.2 the formaldehyde concentration reached a plateau after < 1 hours, while at pH 4 the reaction was slightly slower, reaching the plateau after 3-4 hours.The following formaldehyde release percentages, referring to the weighed sample, were determined: at pH 7.2 after 390 h approx. 25%, at pH 9.2 after 387 h approx. 26%, and at pH 4.0 after 295 h approx. 32% (maximal releasable formaldehyde is specified to be 46.1%).

The results show that formaldehyde is quickly released from mono- and dimethylol ethylene glycol and from the non-identified reaction products of ethylene glycol with formaldehyde. Further release thenoccurs more slowly. Formaldehyde hydrate and ethylene glycol could be demonstrated as hydrolysis products. The quick release at the beginning and the slower yet continuous release at later time points show that there are differences in the formaldehyde release rates of the individual constituents of EUF.

Similar results were obtained in a second study where products of hydrolysis were identified at different concentrations of EUF (100, 50, 10, 1, 0.25 and 0.025%) in phosphate buffer/D2O (pH 7) after 7 days of equilibrium adjustment. Increasing contents of the hydrolysis products ethylene glycol and formaldehyde were observed in parallel to increasing the D2O content. Simultaneously, the content of methylolated ethylene glycols decreased. Both in neat EUF and in diluted solutions reaction products of urea could be identified as urea derivatives but not specified. It can be recognized that on the one hand the reaction products of ethylene glycol with formaldehyde are completely hydrolyzed at low concentrations. On the other hand some of the reaction products of urea with formaldehyde and/or ethylene glycol are more stable under the conditions of the study.