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EC number: 201-114-5
CAS number: 78-40-0
The overall degradation of dibutyl hydrogen phosphate observed with the
determination of the content of dibutyl hydrogen phosphate at 50 °C at
pH 4, 7 and 9 after 5 days is less than 10 %. Dibutyl hydrogen phosphate
is therefore considered to be stable at 50 °C at pH 4, 7 and 9 and no
half-life time and hydrolysis rate were calculated. Because no
degradation was observed, no sterility test was performed in this case.
No further tests at other temperatures are required.
The stability towards hydrolysis 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 are in the
range of 97.5 % to 104.4%. Therefore, dibutyl hydrogen phosphate is
regarded as hydrolytically stable, and no half-life time and hydrolysis
rate were calculated.
The first peak out of three as found in the GC chromatogram of tris(2
-chloro-1 -methylethyl) phosphate containing about 78 - 79% of the total
area was used for interpretation of the hydrolysis rate. The decrease of
the area of the first peak was less than 1% after five days at all three
testsed pH values indicating no hydrolysis. The stability of the two
other isomers was checked by interpretation of the ratio of the peak
areas of the three tris(2 -chloro-1 -methylethyl) phosphate isomers for
a sample from the beginning and from the end of the hydrolyses test. The
equivalence of these ratios indicate that non of the isomers is
susceptible to hydrolyses.
The pH changes during the tests were small and always less than 0.05 pH
The measured temperature range during the test was 49.9 - 50.1°C.
In a GLP-compliant report, preliminary hydrolysis testing was undertaken
at 50ºC for five days. A decrease in concentration of less than 1% was
observed at pH 4, 7 and 9. Based on this result, it is concluded with no
need for further testing in accordance with the OECD guideline, that
TCPP is stable in water at pH 4, 7 and 9 at 25ºC, with a half-life
greater than or equal to one year.
(Geurts and van Veenendaal, 2001)
The substance triethyl phosphate is stable to hydrolysis at pH4, 7 and 9..
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
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.
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.
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