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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
04 April 1995 through 05 May 1995
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
NECTARYL :
- Lot No. : 001143
- Purity : Matches Standard
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Preliminary Test :
A preliminary test was conducted at 50°C at pH4, 7 and 9.
Samples were taken at Time 0, 2.4 hours, 24 hours and 120 hours and analysed by HPLC.
Nectaryl was observed to be stable at pH7 and pH9. A decrease of 17%, c.f. Time 0, was observed in the pH4 buffer solution. pH4 buffer was, thus, studied in more detail.

pH4 - Test 1 at 50°C :
Samples taken at Time 0, 2.4 hours, 24 hours, 120 hours, 360 hours and 650 hours.

A further test (Test 2) was conducted at 70°C at pH4 :
Sampling times : 0, 24, 96, 169 and 288 hours.
Buffers:
Ready-made concentrates (Titrisol, Merck, Darmstadt, DE) were used to prepare the buffer solutions using fresh double-distilled, sterile water.

pH4.00 +/- 0.02 at 20°C : Citric Acid 0.056 mole/L, NaOH 0.11 mol/L, HCl 0.044 mol/L

pH7.00 +/- 0.02 at 20 °C : KH2PO4 0.026 mole/L, Na2HPO4 0.041 mole/L

pH9.00 +/- 0.02 at 20 °C : H3BO3 0.05 mole/L, KCl 0.05 mole/L, NaOH 0.022 mole/L
Details on test conditions:
Test Substance Solution :
A test concentration of 2.4 mg/L was chosen for the study (i.e. 50% of the water solubility).
A stock solution of 240 mg/L of Nectaryl in CH3CN was prepared

Preliminary Test :
Performed at 50 °C.
For each of pH4, 7 and 9, the following operations were performed simultaneously :
- a 250 mL amber glass bottle was filled with 250 mL of the respective buffer solution;
- N2 is bubbled for 5 minutes to remove residual dissolved O2;
- the flask is placed in a water bath at 50 °C;
- 2.5 mL of NECTARYL stock solution added and mixed;
- a 10 mL sample is withdrawn through the stopcock and temperature and pH measured then analysed via HPLC-UV/VIS.
- subsequent sampling after 2.4, 24 and 120 hours of incubation at 50 °C.

No degradation observed for pH7 and pH9.

The incubation for the pH4 incubate was extended and samples taken at :
- 360 and 650 hours.

A second test at pH4 was performed at a temperature of 70 °C :
- Run in duplicate samples;
- Samples taken and analysed at Time 0, 24, 96, 169 and 288 hours;
- Samples analysed by HPLC-UV/VIS.
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
2.22 mg/L
Remarks:
Test item concn determined at 120 hours = 1.84 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
2.3 mg/L
Remarks:
Test item concn determined at 120 hours = 2.20 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
2.35 mg/L
Remarks:
Test item concn determined at 120 hours = 2.27 mg/L
Number of replicates:
Preliminary Test :
pH4 : 1 sample
pH7 : in duplicate
pH9 : 1 sample

pH4 at 70 °C :
In duplicate.
Positive controls:
no
Negative controls:
no
Preliminary study:
Preliminary Test :
A preliminary test was conducted at 50°C at pH4, 7 and 9.
Samples were taken at Time 0, 2.4 hours, 24 hours and 120 hours and analysed by HPLC.
Nectaryl was observed to be stable at pH7 and pH9. A decrease of 17%, c.f. Time 0, was observed in the pH4 buffer solution. pH4 buffer was, thus, studied in more detail.
Transformation products:
no
% Recovery:
83
pH:
3.84
Temp.:
50 °C
Duration:
120 h
Remarks on result:
other: Need to continue to additional testing at pH4
% Recovery:
96
pH:
6.85
Temp.:
50 °C
Duration:
120 h
Remarks on result:
other: Less than 10% degradation observed at 50 °C, T1/2 considered > 1-year at 25°C.
% Recovery:
97
pH:
8.69
Temp.:
50 °C
Duration:
120 h
Remarks on result:
other: Less than 10% degradation observed at 50 °C, T1/2 considered > 1-year at 25°C.
% Recovery:
42
pH:
3.84
Temp.:
50 °C
Duration:
650 h
% Recovery:
10.5
pH:
4
Temp.:
70 °C
Duration:
288 h
Key result
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
210 d
Type:
(pseudo-)first order (= half-life)
Key result
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Key result
pH:
9
Temp.:
25 °C
DT50:
> 1 yr
Validity criteria fulfilled:
yes
Conclusions:
Nectaryl undergoes negligible hydrolysis at pH7 and pH9 (T1/2 > 1 year at 25 °C), whereas a normal pseudo-1st order hydrolysis reaction occurs at pH4 with a derived half-life time of 210 days at 25 °C.
Executive summary:

Nectaryl undergoes negligible hydrolysis at pH7 and pH9 (T1/2 > 1 year at 25 °C), whereas a normal pseudo-1st order hydrolysis reaction occurs at pH4 with a derived half-life time of 210 days at 25 °C.

Description of key information

Nectaryl undergoes negligible hydrolysis at pH7 and pH9 (T1/2 > 1 year at 25 °C), whereas a normal pseudo-1st order hydrolysis reaction occurs at pH4 with a derived half-life time of 210 days at 25 °C.

Key value for chemical safety assessment

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

Additional information

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