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Hydrolysis

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Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2003-04-08 to 2003-05-12
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
not specified
GLP compliance:
no
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The test solutions were sampled at T=0, 2.4 h, and at 120 h.
Buffers:
pH = 4 Buffer (0.01 M Sodium acetate)
Approximately 0.8 g of anhydrous sodium acetate was dissolved per liter of distilled water and the pH adjusted to approximately 4.0 with glacial acetic acid.

pH = 7 Buffer (0.02 M Phosphate buffer)
Approximately 1.4 g of potassium phosphate monobasic anhydrous and 1.7 g of potassium phosphate dibasic anhydrous were dissolved per liter of distilled water and the pH adjusted to approximately 7.0 with 0.1 M sodium hydroxide.

pH = 9 Buffer (0.025 M Sodium Borate buffer)
Approximately 9.5 g of sodium borate decahydrate were dissolved per liter of distilled water and the pH adjusted to approximately 9.0 with 0.1 M hydrochloric acid.
Details on test conditions:
PREPARATION OF TEST SOLUTIONS
A 1.5 mg/L solution of bis(2-ethylhexyl)terephthalate in acetonitrile was prepared. Then, 1 mL of this solution was transferred into a 4-L glass bottled containing 1800 mL of buffer solution, yielding a final concentration of 0.0008 mg/L. Duplicate spiked control solutions were prepared at each pH

Duration:
122 h
pH:
4
Initial conc. measured:
0.001 mg/L
Duration:
122 h
pH:
7
Initial conc. measured:
0.001 mg/L
Duration:
122 h
pH:
9
Initial conc. measured:
0.001 mg/L
Number of replicates:
2
Positive controls:
no
Negative controls:
not specified
Statistical methods:
Not performed due to lack of hydrolysis measured.
Preliminary study:
The test solutions were analyzed only at 120 hours. The 120-hr measured concentrations were compared to the initial nominal concentrations to determine the extent of hydrolysis. Test systems in all three pH buffers had an average percent hydrolysis of <14%
Transformation products:
no
% Recovery:
ca. 100
pH:
4
Temp.:
50 °C
Duration:
122 h
% Recovery:
>= 85.8 - <= 88
pH:
7
Temp.:
50 °C
Duration:
120 h
% Recovery:
>= 84.7 - <= 100
pH:
9
Temp.:
50 °C
Duration:
120 h
Key result
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test

Hydrolysis of Bis(2-ethylhexyl)terephthalate at 50°C Determined by Mass Balance 
Test system Time (h) Concentration (mg/L) Mass balance % Hydrolysis Average Hydrolysys
pH4 120 0.0008 113 -33 -22%
pH4 120 0.0008 112 -12
pH7 120 0.0008 85.8 14 14%
pH7 120 0.0008 88 12
pH9 120 0.0008 84.7 15 -4%
pH9 120 0.0008 104 -4

In this test, the test solutions were analyzed only at 120 hours. The 120-hr measured concentrations were compared to the initial nominal concentrations to determine the extent of hydrolysis. Test systems in all three pH buffers had an average percent hydrolysis of :Sl 4 %.

Validity criteria fulfilled:
not specified
Remarks:
Preliminary study was performed.
Conclusions:
Results for the preliminary test suggest that little, if any, hydrolysis occurs at the pH range of 4 to 9.
Executive summary:

A second hydrolysis test of bis (2-ethylhexyl) terephthalate [non-radiolbelled] was performed at pH values of 4, 7, and 9 at 50 °C. Mass balance data indicate that little, if any, hydrolysis occurs at the pH range of 4-9. The conclusion is limited by the uncertainty of the aqueous solubility of the test substance under the hydrolysis test conditions and the effect it may have had on the results.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2003-04-08 to 2003-05-12
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
not specified
GLP compliance:
no
Radiolabelling:
yes
Analytical monitoring:
yes
Details on sampling:
In the initial test using the radiolabeled test substance, the test solutions were sampled at T=0, 2.4 h, and at 120 h.
Buffers:
pH = 4 Buffer (0.01 M Sodium acetate)
Approximately 0.8 g of anhydrous sodium acetate was dissolved per liter of distilled water and the pH adjusted to approximately 4.0 with glacial acetic acid.

pH = 7 Buffer (0.02 M Phosphate buffer)
Approximately 1.4 g of potassium phosphate monobasic anhydrous and 1.7 g of potassium phosphate dibasic anhydrous were dissolved per liter of distilled water and the pH adjusted to approximately 7.0 with 0.1 M sodium hydroxide.

pH = 9 Buffer (0.025 M Sodium Borate buffer)
Approximately 9.5 g of sodium borate decahydrate were dissolved per liter of distilled water and the pH adjusted to approximately 9.0 with 0.1 M hydrochloric acid.
Details on test conditions:
PREPARATION OF TEST SOLUTIONS
Bis (2-ethylhexyl) terephthalate [carboxyl-14C]:
A concentrated stock solution of the radiolabeled substance was prepared by weighing approximately 0.015 g of the test substance into a 10-mL volumetric flask and diluting to volume with acetonitrile. A dilute stock was prepared by diluting 0.025 mL of the concentrated stock to 50 mL with acetonitrile. The test solutions were prepared by transferring 2.0 mL of the diluted stock into each of three 1-L glass reservoirs containing 1 L of pH 4,7,and 9 buffers. Test solutions at each pH were prepared in triplicate. The nominal initial concentration of the test substance was 0.0015 mg/L. Each reservoir was capped and placed in a 50 °C water bath.

Duration:
0 h
pH:
4
Initial conc. measured:
1.43 µg/L
Duration:
122 h
pH:
4
Initial conc. measured:
0.984 µg/L
Duration:
0 h
pH:
7
Initial conc. measured:
1.07 µg/L
Duration:
122 h
pH:
7
Initial conc. measured:
1.36 µg/L
Duration:
0 h
pH:
9
Initial conc. measured:
1.57 µg/L
Duration:
122 h
pH:
9
Initial conc. measured:
1.49 µg/L
Number of replicates:
3
Positive controls:
no
Negative controls:
not specified
Statistical methods:
Not performed due to lack of hydrolysis measured.
Preliminary study:
Hydrolysis was based on both solution concentrations and mass balance determinations. The mass balance data indicate that even at 50 °C little if any hydrolysis occurs in the pH range of 4 to 9.
Transformation products:
no
% Recovery:
ca. 100
pH:
4
Temp.:
50 °C
Duration:
>= 0 - <= 120 h
Remarks on result:
other: Radiolabelled C-14
% Recovery:
ca. 87
pH:
7
Temp.:
50 °C
Duration:
>= 0 - <= 120 h
% Recovery:
ca. 99
pH:
9
Temp.:
50 °C
Duration:
>= 0 - <= 120 h
Key result
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test

Hydrolysis of Radiolabeled DOTP at 50 °C Determined by Mass Balance
Test System Time (h) Concentration (µg/L) % Hydrolysis
pH 4 0 1.43 nr
pH 4 2.4 1.66 -16
pH 4 122 0.984 38
pH 7 0 1.07 nr
pH 7 2.4 1.21 -12
pH 7 122 1.36 -26
pH 9 0 1.7 nr
pH 9 2.4 * nr
pH 9 122 0.858 50
pH 9 B 0 1.57 nr
pH 9 B 2.4 1.56 1.3
pH 9 B 122 1.49 5.7
Note: the pH 9 buffer system was retested and reported as test system pH 9 B.
*No test substance detected; no assignable cause.
nr = not reported

No significant hydrolysis occurred within 2.4 hours in any of the test systems. At 120 hours, the test substance concentration in the pH 7 and 9 buffer systems had changed less than 1 O % from the time O value. However, the measured test substance concentration in the pH 4 buffer system was approximately 38% less than the T=O concentration. Other studies in this laboratory have shown that the very low water solubility of bis(2-ethylhexyl)terephthalate (0.0004 mg/Lat 20°C) and its hydrophobic character often contributed to adsorption problems. We performed a mass balance study to determine if adsorption was contributing to the observed decrease in test chemical concentration at pH 4. The remaining test solutions in the pH 4 and pH 7 buffer test systems were extracted with methylene chloride including rinsing of the original test vessels. Due to insufficient sample solution, the pH 9 buffer system tested 4/16-4/22 could not be analyzed. The pH 9 buffer system was retested 4/22-4/27. The mass balance results are shown in Table 2. The mass balance results at all pHs are 100%± 15%. At pH 4, the measured mass balance was 111 %, indicating that adsorption could have been a factor in the observed decrease in test chemical concentration.

Validity criteria fulfilled:
not specified
Remarks:
Preliminary study was performed.
Conclusions:
Results for the preliminary test suggest that little, if any, hydrolysis occurs at the pH range of 4 to 9.
Executive summary:

A preliminary hydrolysis test of bis (2-ethylhexyl) terephthalate [carboxyl-14C] was performed at pH values of 4, 7, and 9 at 50 °C. Mass balance data indicate that little, if any, hydrolysis occurs at the pH range of 4-9. The conclusion is limited by the uncertainty of the aqueous solubility of the test substance under the hydrolysis test conditions and the effect it may have had on the results.

Description of key information

Experimental data supported by modeled values.

Key value for chemical safety assessment

Additional information

Hydrolysis studies were performed first using bis(2-ethylhexyl)terephthalate[carboxyl-14C] and then a nonlabeled sample of bis(2-ethylhexyl)terephthalate. In the initial tests using the 14C-labeled sample of test chemical, hydrolysis was assessed based on both solution concentrations and mass balance determinations. In the second tests using the non-labeled test chemical, hydrolysis was assessed using mass balance data. The mass balance data indicate that even at 50°C little if any hydrolysis of bis(2-ethylhexyl)terephthalate occurs in the pH range of 4 to 9. This is supported by SPARC calculations that indicate that hydrolyses is unlikely to occur. Also, as this substance is readily biodegradable Column 2 of Annex 8 indicates that a hydrolysis study is not required.