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Hydrolysis

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In a read across approach with dibutyl hydrogen phosphate (CAS No. 107-66-4), the behaviour of bis(2-ethylhexyl) hydrogen phosphate against hydrolysis is assessed. Dibutyl hydrogen phosphate is shown to be stable at pH 4, 7 and 9 at 50°C. Therefore it can be assumed that also bis(2-ethylhexyl) hydrogen phosphate is stable against hydrolysis.

Key value for chemical safety assessment

Additional information

In general according to column 2 of REACH Annex VIII, the study does not need to be conducted as bis(2 -ethylhexyl) hydrogen phosphate is readily biodegradable.

Nevertheless, as there is no data available for bis(2-ethylhexyl) hydrogen phosphate, read across with dibutyl hydrogen phosphate (CAS No. 107-66-4) is proposed to cover this endpoint.

Dibutyl hydrogen phosphate and bis(2-ethylhexyl) hydrogen phosphate have very similar chemical structures and their main physico-chemical parameters (vapour pressure, water solubility, octanol/water partition coefficient, organic carbon partition coefficient and dissociation constant) are in the same range. Therefore a read across between this two substances to cover physico-chemical and ecotoxicological endpoints for bis(2-ethylhexyl) hydrogen phosphate seems to be justified.

More details regarding the read across justification are depicted in the annex of the Chemical Safety Report (CSR).

The stability towards hydrolysis of dibutyl hydrogen phosphate was investigated at pH 4, 7 and 9 at 50°C according to OECD Guideline 111 (Hydrolysis as a Function of pH). After 5 days the recoveries of dibutyl hydrogen phosphate were in the range of 97.5 % to 104.4%. The stability was monitored by HPLC analysis using MS-detection.

Dibutyl hydrogen phosphate is found to be hydrolytically stable at 50°C at all three pH-values. Therefore it can be assumed that dibutyl hydrogen phosphate is also stable at 25 °C and no half-life times and hydrolysis rates were calculated.

Based on the results of the hydrolysis study with dibutyl hydrogen phosphate it can be assumed that like dibutyl hydrogen phosphate bis(2-ethylhexyl) hydrogen phosphate is stable against hydrolysis.