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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
12/10/1995 - 09/06/1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were analysed after incubation for 0.25, 2.4, 24, 95/96, 118/120 and 170 hours.
Buffers:
Buffer solutions were created using chemicals described in Table 1 in order to produce solutions of pH 4.0, 7.0, 9.0, 11.0, and 13.0. The test solutions were adjusted to within ± 0.05 pH of the desired value before being purged with nitrogen.
Duration:
170 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
1.85 mg/L
Duration:
170 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
1.91 mg/L
Duration:
170 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
2.05 mg/L
Duration:
120 h
pH:
11
Temp.:
50 °C
Initial conc. measured:
2.1 mg/L
Duration:
96 h
pH:
13
Temp.:
50 °C
Initial conc. measured:
2.05 mg/L
Number of replicates:
2
Positive controls:
no
Negative controls:
no
Statistical methods:
not reported
Preliminary study:
The preliminary test was the only test reported in the study as less than 10% degradation was observed at pH 4, 7 and 9 in the preliminary test.
The results are summarised in Table 2. There was no significant change in the concentration of dinotefuran when incubated at pH 4, pH 7 or pH 9 at 50ºC. Less than 10% degradation was observed.

As there was no degradation at lower pH values, no rate constants were calculated. It was possible to calculate rate constants at pH 11 and 13.
Ln Ct (pH 11 and 50ºC) = 0.710-1.55 x10¯²t,
Ln Ct (pH 13 and 50ºC) = 0.751-1.65 x10¯²t

There was less than 10% degradation of dinotefuran over 170 hours when incubated at pH 4, pH7 or pH9 at 50ºC. The half- life at pH 11 was 45 hours. The half-life at pH 13 was 4.2 hours.

There were no significant transformation products at the required pH values. The only transformation product observed in any significant amounts was found at pH 11 and 13 and identified as 1-methyl-3-(tetrahydro-3-furylmethyl)urea (UF) by co-chromatography and LC-MS/MS with reference standard.
Transformation products:
yes
No.:
#1
Remarks on result:
other: Dinotefuran was hydrolytically stable at pH 4,7 and 9 at 50ºC

Table 1:           Type and composition of buffer solutions (specify kind of water if necessary)

pH

Type of buffer (final molarity)

Composition

4

Not stated

Disodium hydrogen orthophosphate dodecahydrate (13.8g) and citric acid monohydrate (6.45g) were dissolved in purified water (950ml) and the pH adjusted to 4.0 with 1M hydrochloric acid. The volume was adjusted to 1000 ml with purified water.

7

Not stated

Potassium dihydrogen orthophosphate (3.4g) was dissolved in purified water (950ml). 1M sodium hydroxide (15ml) was added and the pH adjusted to 7.0 with 1M hydrochloric acid. The volume was adjusted to 1000ml with purified water.

9

Not stated

Disodium tetraborate decahydrate (16.6g) and potassium dihydrogen orthophosphate (1.80g) were dissolved in purified water (950ml) and the pH adjusted to 9.0with 1M hydrochloric acid. The volume was adjusted to 1000ml with purified water.

11

Not stated

Glycine (7.54g) and sodium chloride (5.84g) were dissolved in 1000 ml of purified water (Solution A). Sodium hydroxide (2.04g) was dissolved in 500ml of purified water (Solution B). Portions of Solution A and Solution B (51ml and 49ml respectively) were mixed thoroughly.

13

Not stated

Glycine (7.54g) and sodium chloride (5.84g) were dissolved in 1000ml of purified water (Solution A). Sodium hydroxide (2.04g) was dissolved in 500ml of purified water (Solution B). Portions of Solution A and Solution B (7.5 ml and 92.5 ml respectively) were mixed thoroughly.

 

Table 2:           Concentration (mg/l) of dinotefuran (parent compound) with time at various pH values

 

Days of incubation

0

2.4

24

95/96

118/120

170

pH 4

1.85

1.85

1.87

1.83

1.84

1.83

pH 7

1.91

1.89

1.91

 

1.88

1.84

pH 9

2.05

2.07

2.01

 

1.93

1.84

pH 11

2.10

1.97

1.34

0.46

0.32

 

pH 13

2.05

1.48

0.04

 

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
Dinotefuran can be considered as stable to hydrolysis under environmentally relevant conditions with a half life greater than one year as it was stable at pH 4, 7 and 9 at 50ºC. At pH 11 and 13 and 50ºC, hydrolysis to 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) was observed with half lives of 45 hours and 4.2 hours respectively. Although not required by the guideline, degradate UF was identified by LC-MS/MS.

Description of key information

Key value for chemical safety assessment

Half-life for hydrolysis:
7 d
at the temperature of:
50 °C

Additional information