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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
April 26, 2006 to May 23, 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EPA OPPTS 835.2110 (Hydrolysis as a Function of pH)
Version / remarks:
Product Properties Test Guidelines. 1998. OPPTS 835.2110, Hydrolysis as a Function a/pH.
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
Organisation for Economic Co-operation and Development. 198 i. Gudeline for Testing of Chemicals, 111: Hydrolysis as a Function of pH.
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
No further details specified
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Triplicate samples of each solution were taken and diluted in 10% acetonitrle: 90% HPLC-grade water for immediate analysis.
Buffers:
Aqueous buffer solutions (1000 mL each) were prepared using HPLC-grade reagent water and salts, acids and bases as follows:
pH 4 – Mixed 8.203 g of sodium acetate and 33.382 g acetic acid in volumetric flask with reagent-grade water. The final volume of the solution was adjusted to 2000 mL with reagent-grade water.
pH 7 – Mixed 13.609 g potassium dihydrogen phosphate and 2.370 g sodium hydroxide in a volumetric flask with reagent-grade water. The final volume of the solution was adjusted to 2000 mL with reagent-grade water.
pH 9 – Mixed 7.455 g potassium chloride, 6.183 g boric acid and 1.704 g sodium hydroxide in a volumetric flask with reagent-grade water. The final volume of the solution was adjusted to 2000 mL with reagent-grade water.
Details on test conditions:
Test System
The study was conducted using sterile solutions buffered at pH 4, 7 and 9. Acetate (pH 4), phosphate (pH 7) and borate (pH 9) buffers were used.
The pH of each aqueous buffer solutions was measured using a pH meter with an accuracy of 0.01 pH unit. Prior to use, the resulting pH-adjusted aqueous buffer solutions used for testing were vacuum filtered through 0.2 μm filters.

Stock Preparation
A stock solution of PHT4 was prepared by accurately weighting 0.1000 g of the test substance on an analytical balance. The test substance was transferred if a 100 mL class A volumetric flask and brought to volume using tetrahydrofuran. The primary stock solution contained 1.00 mg/mL of PHT4 and was used to fortify the buffer solutions and prepare the calibration standard in 10% acetonitrile : 90% HPLC-grade water. The following shows the dilution scheme for the sort of calibration standards:
Stock Concentration (mg/mL) Aliquot (mL) Final Volume (mL) Standard Centration (mg/L)
1.00 0.100 100 1.00
1.00 0.250 100 2.50
1.00 0.500 100 5.00
1.00 0.750 100 7.50
1.00 1.00 100 10.0

Preliminary Test
Preliminary test samples were prepared in volumetric flasks a nominal concentration of 9.00 mg/L. Samples were prepared by fortifying 100 mL samples of pH 4, 7 and 9 buffer solutions using a PHT4 stock solution prepared in tetrahydrofuran. Triplicate samples of each solution were taken and diluted in 10% acetonitrile : 90% HPLC-grade water for immediate analysis, and remaining solutions of each were placed into an incubator set at approximately 50 °C for a period of five days. On the fifth day, the samples were removed from the incubator and triplicate sample of each test vessel were diluted in 10% acetonitrile : 90% HPLC-grade water for PHT4 analysis.

Temperature Measurements
The temperatures of the incubated samples during the preliminary test was monitored using a min./max. thermometer. Samples were maintained at 50 ± 1.0 °C.
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
9 mg/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
9 mg/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
9 mg/L
Number of replicates:
Triplicate samples were prepared.
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
Not specified
Preliminary study:
Degradation of PHT4 was <10% in the pH 4, 7 and 9 test systems.
Transformation products:
not measured
% Recovery:
100
pH:
4
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
% Recovery:
100
pH:
7
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
% Recovery:
100
pH:
9
Temp.:
50 °C
Duration:
5 d
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
4
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
7
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
9
Temp.:
50 °C
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
The hydrolytic stability of PHT4 in the preliminary test was evaluated at pH 4 (acetate buffer), pH 7 (phosphate buffer) and pH 9 (borate buffer) at 50 °C over a five-day period (Day 0 and Day 5). Samples were prepared at a nominal concentration of 9.00 mg/L in each buffer and analyzed in triplicate in Days 0 and 5 of the test. Mean recoveries expressed as a percent of nominal on Day 0 were 99.3%, 102% and 102% for the pH 4, 7 and 9 levels, respectively. Mean recoveries expressed as a percent of nominal on Day 5 were 101%, 100% and 102% for the pH 4, 7 and 9 levels, respectively. As degradation was <10% in the pH 4, 7 and 9 test systems, no further testing was performed.
Results with reference substance:
Not specified

 Preliminary Study Sample Recoveries for PHT4 in Buffered Solutions of pH 4, 7 and 9

Sample Number 616C-107-)

Nominal Concentration (mg/L)

pH

Sampling Interval (Day)

Analytical Result (mg/L)

Mean Analytical Result (mg/L/SD)

Mean Percent Recovery (%)

pH4-1

pH4-2

pH4-3

9.00

9.00

9.00

4

4

4

0

0

0

8.90

8.97

8.94

 

8.94

0.0347

 

 

99.3

pH4-4

pH4-5

pH4-6

9.00

9.00

9.00

4

4

4

5

5

5

9.04

9.05

9.04

 

9.05

0.00612

 

 

101

pH7-1

pH7-2

pH7-3

9.00

9.00

9.00

7

7

7

0

0

0

9.14

9.21

9.28

 

9.21

0.0723

 

 

102

pH7-4

pH7-5

pH7-6

9.00

9.00

9.00

7

7

7

5

5

5

9.00

9.00

8.99

 

8.99

0.0329

 

 

100

pH9-1

pH9-2

pH9-3

9.00

9.00

9.00

9

9

9

0

0

0

9.12

9.14

9.16

 

9.14

0.0207

 

 

102

pH9-4

pH9-5

pH9-6

9.00

9.00

9.00

9

9

9

5

5

5

9.13

9.14

9.15

 

9.14

0.00848

 

 

102

Results were generated using Excel 2000 in the full precision mode. Manual calculations with rounded values may differ

 

Validity criteria fulfilled:
not specified
Conclusions:
Degradation of PHT4 was <10% in the pH 4, 7 and 9 test systems, therefore, no further testing was performed.
Executive summary:

The objective of the study was to determine the rate of hydrolysis of PHT4 in aqueous media in the environmentally relevant pH range of 4-9 at approximately 25 °C.

 

The procedures used in the study were based on those found in the US EPA Product Properties Test Guideline 835.2110 and OECD Guideline for Testing of Chemicals, 111.

 

The hydrolytic stability of PHT4 in the preliminary test was evaluated at pH 4 (acetate buffer), pH 7 (phosphate buffer) and pH 9 (borate buffer) at 50 °C over a five-day period (Day 0 and Day 5). Samples were prepared at a nominal concentration of 9.00 mg/L in each buffer and analyzed in triplicate in Days 0 and 5 of the test. Mean recoveries expressed as a percent of nominal on Day 0 were 99.3%, 102% and 102% for the pH 4, 7 and 9 levels, respectively. Mean recoveries expressed as a percent of nominal on Day 5 were 101%, 100% and 102% for the pH 4, 7 and 9 levels, respectively. As degradation was <10% in the pH 4, 7 and 9 test systems, no further testing was performed.

 

Degradation of PHT4 was <10% in the pH 4, 7 and 9 test systems, therefore, no further testing was performed.

Description of key information

Degradation of PHT4 was <10% in the pH 4, 7 and 9 test systems, therefore, no further testing was performed.

Key value for chemical safety assessment

Additional information

The hydrolytic stability of PHT4 in the preliminary test was evaluated at pH 4 (acetate buffer), pH 7 (phosphate buffer) and pH 9 (borate buffer) at 50 °C over a five-day period (Day 0 and Day 5). Samples were prepared at a nominal concentration of 9.00 mg/L in each buffer and analyzed in triplicate in Days 0 and 5 of the test. Mean recoveries expressed as a percent of nominal on Day 0 were 99.3%, 102% and 102% for the pH 4, 7 and 9 levels, respectively. Mean recoveries expressed as a percent of nominal on Day 5 were 101%, 100% and 102% for the pH 4, 7 and 9 levels, respectively. As degradation was <10% in the pH 4, 7 and 9 test systems, no further testing was performed.

 

Degradation of PHT4 was <10% in the pH 4, 7 and 9 test systems, therefore, no further testing was performed.