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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:
2013-03-12 - 2013-08-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The GLP study was conducted according to an internationally accepted guideline. All study parameters are based on the specific guideline.
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Details on sampling:
Samples were taken at the beginning of the test and after 2.4 and 120 hours at pH 4, pH 7 and pH 9 at 50°C.
Buffers:
The test was carried out at three different pH values: 4.0, 7.0 and 9.0.
For this purpose, buffer solutions were prepared using reagent grade chemicals and distilled or deionized water. Applicable buffer systems are described in the Appendix of EC method C.7 (92/69/EC), OECD guideline 111 or BBA Merkblatt Nr.55, Teil I.
The citrate buffer pH 4, the phosphate buffer pH 7 and the borate buffer
pH 9 were prepared in a concentration of 0.05 M on the basis of the undissociated acids.
The pH value of the buffer solutions used during the test were determined with a calibrated pH meter at the selected temperature with a precision of 0.1 pH units.
Details on test conditions:
The test was carried out using a thermostatically controlled water bath at ± 0.5 °C of the chosen temperature. The temperature was kept and measured to within ± 0.1 °C. Photolytic interference was avoided. All suitable precautions were taken to exclude dissolved oxygen (bubbling the buffer with helium for five minutes before preparing the test solution).
Duration:
120 h
pH:
4
Temp.:
50 °C
Initial conc. measured:
46.96 mg/L
Duration:
120 h
pH:
7
Temp.:
50 °C
Initial conc. measured:
46.56 mg/L
Duration:
120 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
55.4 mg/L
Positive controls:
no
Negative controls:
no
Transformation products:
not measured
pH:
4
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified
pH:
7
Temp.:
25 °C
DT50:
> 1 yr
Type:
not specified

Time course ofMPAconcentration at pH 4 at 50 °C

Time

Determined Content

of MPA in Sample

Actual concentration

[h]

[mg/L]

in % of initial conc.

0

46.96

100.0

2.4

46.88

99.8

120

47.44

101.0

Mean

47.09

100.3

Std. Dev.

0.30

0.64

RSD

0.64

0.64

Time course ofMPAconcentration at pH 7 at 50 °C

Time

Determined Content

of MPA in Sample

Actual concentration

[h]

[mg/L]

in % of initial conc.

0

46.56

100.0

2.4

47.92

102.9

120

47.64

102.3

Mean

47.37

101.7

Std. Dev.

0.72

1.54

RSD

1.52

1.52

Time course ofMPAconcentration at pH 9 at 50 °C

Time

Determined Content

of MPA in Sample

Actual concentration

[h]

[mg/L]

in % of initial conc.

0

55.40

100.0

2.4

55.08

99.4

120

56.56

102.1

Mean

55.68

100.5

Std. Dev.

0.78

1.41

RSD

1.40

1.40

Validity criteria fulfilled:
yes
Conclusions:
The degradation of MPA was less than 10 % at pH 4, pH 7 and pH 9 at 50°C over a period of 120 hours. Therefore the corresponding half life time at 25°C can be estimated to be longer than one year.
Executive summary:

The abiotic degradation of MPA as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (92/69/EC).

It was shown that the hydrolysis of MPA is negligible within the pH range relevant for natural environments (pH 4 to pH 9). The half life times at pH 4, 7 and 9 are expected to be above one year at 25 °C in each case. Cause the test item is stable to hydrolysis no further hydrolysis tests are necessary. The degradation of MPA was less than 10 % at pH 4, pH 7, pH 9 at 50°C over a period of 120 hours. Therefore the corresponding half life time at 25°C can be estimated to be longer than one year.

Description of key information

The abiotic degradation of MPA as a function of pH in aqueous solution was determined according to OECD guideline 111 and EC method C.7 (92/69/EC).

It was shown that the hydrolysis of MPA is negligible within the pH range relevant for natural environments (pH 4 to pH 9). The half life times at pH 4, 7 and 9 are expected to be above one year at 25 °C in each case. Cause the test item is stable to hydrolysis no further hydrolysis tests are necessary. The degradation of MPA was less than 10 % at pH 4, pH 7, pH 9 at 50°C over a period of 120 hours. Therefore the corresponding half life time at 25°C can be estimated to be longer than one year.

Key value for chemical safety assessment

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

Additional information

The half life time of N-(3(5)-Methyl-1 H-pyrazol-1 -yl-methyl)-acetamid at 25°C was estimated to be longer than one year.