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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
30 july 2012 to 18 March 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study was conducted in accordance with international guidelines (OECD 111) and in accordance with GLP. All relevant validity criteria were met.
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were taken on day zero and day 5 and tris(2-ethylhexyl)phosphate from the duplicate test vessels.
Buffers:
Citrate buffer (Citric acid, sodium hydroxide and hydrogen chloride) pH 4
Phosphate buffer (Di-sodium hydrogen phosphate and potassium dihydrogen phosphate) pH 7
Borate buffer (Boric acid, potassium chloride and sodium hydroxide) pH 9
Borate buffer (Boric acid, potassium chloride and sodium hydroxide) pH 10
Details on test conditions:
Only a preliminary test was run. The test was conducted at 50 ± 5 °C, at pH 4, 7 and 9. The pH was acheived by using the varying buffer solutions, pH was checked with a pH meter. Tris(2-ethylhexyl) phosphate (7 mg) was added to 1 mL of tetrahydrofuran in a volumetric flask, and 99 mL of Milli-Q water was added to create a total working volume of 100 mL, this was the stock solution. To make the test solutions 25 mL of stock solution was added to 25 mL of the correct pH buffered solution (i.e. pH 4, 7 or 9). The pH was then measured with a clibrated pH meter. Eight 2 mL aliquots were taken and placed into vials, two were taken for immediate analysis, 2 were frozen at -20 °C. The other 4 aliquots were wrapped in aluminium foil and placed in a 50 °C controlled temprteture chamber for 5 days. This procedure was the same for each pH level tested. Therefore a total of 24 aliquots were made. The concntration of the test substance was determined for each pH, and were as indicated. Standard stocks of known of a concentration were also made to derive a calibration curve for analysis.
Duration:
5 d
pH:
4
Temp.:
50
Initial conc. measured:
35.56 mg/L
Duration:
5 d
pH:
7
Temp.:
50
Initial conc. measured:
34.85 mg/L
Duration:
5 d
pH:
9
Temp.:
50
Initial conc. measured:
31.77 mg/L
Number of replicates:
The experiment was conducted in duplicate and for each sample 2 measurements were taken at each time point.
Preliminary study:
The results of the preliminary test showed that the Tris(2-ethylhexyl) phosphate) concentration decreased by 6.21 % at pH 4.0; 9.53 % at pH 7.0 and 7.67 % at pH 9.0, indicating that Tris(2-ethylhexyl) phosphate) is stable at pHs 4, 7 and 9.
Test performance:
When the calculations obtained for electronics spreadsheet are compared to values elaborated by manual calculator, small differences can be observed among the results. This is due to the number of decimal approaches used in each different process. However these differences do not compromise the study, as they are just rounding differences.
Transformation products:
not measured
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
the test substance did not significantly degrade < 10 % over 5 days.

Table 1: Concentration of test substance measured at time zero and 5 days after test initiation in each sample, with calculated degradation %.

Incubation time (d)

Buffer pH

4

7

9

0

Test solution pH

4.00

6.99

9.01

Sample 1 mg/L

33.55

36.49

34.79

34.13

32.12

31.97

Sample 2 mg/L

36.90

35.30

34.93

35.54

31.61

31.37

Mean mg/L

35.56

34.85

31.77

5

Sample 1 mg/L

33.23

34.19

31.92

31.36

30.21

29.27

Sample 2 mg/L

32.41

33.57

31.77

31.06

28.92

-

Mean mg/L

33.35

31.53

29.33

Deg. % after 5 d

6.21

9.53

7.67

Validity criteria fulfilled:
yes
Conclusions:
The test substance is not degraded by hydrolysis at any of the tested pH levels. Tris(2-ethylhexyl) phosphate is considered stable with half-life longer than one year (t1/2 > 1 year).
Executive summary:

The stability to hydrolysis of Tris(2-ethylhexyl) phosphate was performed at pH 4, pH 7 and pH 9. The study was conducted with Tris (2-ethylhexyl) phosphate technical grade for five days for 50 ± 0.5.

In a preliminary test conducted at 50 ± 0.5 °C, it were found that at pHs 4, 7 and 9, the Tris(2-ethylhexyl) phosphate concentration did not decrease more than 10 % during an incubation period of 5 days.

Tris(2-ethylhexyl) phosphate is considered stable with half-life longer than one year (t1/2 > 1 year).

Description of key information

Hydrolytic half-life = >1 year (25°C); OECD 111; Severino (2013)

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
25 °C

Additional information

In a single key study, the stability to hydrolysis of Tris(2-ethylhexyl) phosphate was performed at pH 4, pH 7 and pH 9 in accordance with OECD 111 (Severino, 2013).. The study was conducted with Tris (2-ethylhexyl) phosphate technical grade for five days for 50 ± 0.5. In a preliminary test conducted at 50 ± 0.5 °C, it were found that at pHs 4, 7 and 9, the Tris(2-ethylhexyl) phosphate concentration did not decrease more than 10 % during an incubation period of 5 days. Tris(2-ethylhexyl) phosphate is considered stable with half-life longer than one year (t1/2 > 1 year).