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Description of key information

The substance triethyl phosphate is stable to hydrolysis at pH4, 7 and 9..  

Key value for chemical safety assessment

Additional information

As no study for the hydrolysis for triethylphosphate at pH 4, 7 and 9 is available, data from similar alkyl phosphate in a read-across approach were taken (1. dibutyl phosphate, 2. tris-chlorpropyl phosphate, 3. supporting evidence for stability is given by literature data for non-guideline studies for triethyl phosphate)

1. The stability towards hydrolysis of dibutyl 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 the substance were in the range of 97.5 % to 104.4%. The stability was monitored by HPLC analysis using MS-detection. Dibutyl phosphate is found to be hydrolytically stable at 50°C at all three pH-values. Therefore it can be assumed that the substance is also stable at environmental relevant conditions.

2. The result of the GLP-complient report (Geurts & van Veenendaal, 2001) according to OECD 111 shows that TCPP_Tris(2 -chloro-1 -methylethyl) phosphate is stable in water. No degradation was found at 50°C at pH 4, 7 and 9 during the test period of 5 days. It is discussed in the European Union Risk Assessment Report of tri(2 -chloro-1-methylethyl) phosphate that phosphate esters are known to hydrolyse although this is expected to be slow under environmentally relevant conditions.

3. Mabey & Mill (1978) reviewed the available published hydrolysis data for a number of chemicals including phosphoric acid esters. Neutral hydrolysis is reported to be the dominant process for this class of compounds (phosphoric acid esters) at pH7. For triethyl phosphate, a half-life of 5.5 years at 25°C is calculated, based on the rate of hydrolysis at neutral pH.  The second order alkaline hydrolysis rate constant is estimated to be 1.75 x 10 -5 M-1 sec-1 at 27 degrees Celsius (Wolfe, 1980).

The substance triethyl phosphate is stable to hydrolysis under normal environmental conditions.

Two studies from similar phosphate esters are used in a read-across approach. The read-across justification is attached to the IUCLID file in chapter 13.