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Environmental fate & pathways

Hydrolysis

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Endpoint:
hydrolysis
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
[Please provide information for all of the points below. Indicate if further information is included as attachment to the same record, or elsewhere in the dataset (insert links in 'Cross-reference' table)]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
[Describe why the read-across can be performed (e.g. common functional group(s), common precursor(s)/breakdown product(s) or common mechanism(s) of action]

The read-across target substance EP-49-10P2 is composed of a mixture of phosphate esters with bisphenol A diglycidylether (BADGE, CAS 1675-54-3, EC 216-823-5) that is dissolved in BADGE. The amount of esters in the target substance EP-49-10P2 ranges between 10% and 20%; the large rest is BADGE. Therefore, BADGE can be used as read-across source substance.

Based on the high content of BADGE (80-90%) and on the fact that the phosphate esters have higher molecular weights (MW > 1200 Da – approx. 3500 Da) and accordingly lower bioavailability it is concluded that the toxic and eco-toxic potential of EP-49-10P2 will be the same as that of BADGE. With the phosphate esters no hazardous functional groups are introduced.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
[Provide here, if relevant, additional information to that included in the Test material section of the source and target records]

3. ANALOGUE APPROACH JUSTIFICATION
[Summarise here based on available experimental data how these results verify that the read-across is justified]

No experimental data from toxicological or eco-toxicological studies with the target substance EP-49-10P2 are available for comparison of effects. However, based on the composition of EP-49-10P2 it is considered justified to make read-across from study results obtained with the read-across source substance BADGE in order to fulfil the information requirements for REACH registration of EP-49-10P2.
Reason / purpose for cross-reference:
read-across source
Transformation products:
not measured
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
116 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
86 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
171 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose for cross-reference:
reference to same study
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
no
Remarks:
Not specified in report
Qualifier:
according to guideline
Guideline:
other: EEC Test Method A6
Deviations:
yes
Remarks:
24 hours was used to reach equilibrium
GLP compliance:
yes (incl. QA statement)
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
pH 4: Citric acid
pH 7: disodium tetraborate
pH 9: disodium tetraborate
pH 11: disodium tetraborate
Details on test conditions:
Test solutions of 100 ml at 1.93 mg/l test material were perpared by adding the appropriate amount of stock solution (1 ml) in acetonitrile to the preheated buffer solution (50°C). Solutions were shaken and placed in a thermostatic water bath in the dark.
a preliminary test and two definitve tests were performed with the following sampling times (hours):
preliminary: 0,3 ,6, 24
Test I: 0, 1.5, 3, 4.5, 6, 7.5
Test II: 0, 2, 4, 21, 23.5

Completely hydrolysed solution was prepared in order to verify that hydrolysis products do not co-elute with the parent material. Solutions were prepared in pH 11 buffer and incubated at 50°C for 24 hrs.
Duration:
0 h
pH:
4
Temp.:
50
Initial conc. measured:
1.377 mg/L
Duration:
0 h
pH:
7
Temp.:
50
Initial conc. measured:
1.274 mg/L
Duration:
0 h
pH:
9
Temp.:
50
Initial conc. measured:
1.311 mg/L
Duration:
0 h
pH:
4
Temp.:
38
Initial conc. measured:
1.193 mg/L
Duration:
0 h
pH:
7
Temp.:
38
Initial conc. measured:
1.194 mg/L
Duration:
0 h
pH:
9
Temp.:
38
Initial conc. measured:
1.153
Number of replicates:
1 per Test and pH value
Transformation products:
not measured
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
116 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
0.01 h-1
DT50:
86 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
pH:
9
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
171 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: extrapolated based on Arrhenius equation
Preliminary test
  pH Temperature Tiime conc. [mg/l] ln(conc.)
4 50 0 1.127 0.120
4 50 3 0.951 -0.050
4 50 6 0.665 -0.408
4 50 24 0.176 -1.737
7 50 0 1.184 0.169
7 50 3 0.907 -0.098
7 50 6 0.665 -0.408
7 50 24 0.203 -1.595
9 50 0 1.112 0.106
9 50 3 0.957 -0.044
9 50 6 0.772 -0.259
  9 50 24 0.242 -1.419
Kinetic analysis
  pH=4 pH=7 pH=9
Intercept 0.124 0.0077 0.126
gradient -0.078 -0.061 -0.064
standard error of gradient 0.003 0.006 0.001
half-life [hr] 8.9 11.3 10.8
r^2 0.996 0.979 0.999
Test II:
pH Temperature Tiime conc. [mg/l] ln(conc.)
4 50 0 1.377 0.320
4 50 1.5 1.188 0.172
4 50 3 1.008 0.008
4 50 4.5 0.898 -0.108
4 50 6 0.741 -0.300
4 50 7.5 0.665 -0.408
7 50 0 1.274 0.242
7 50 1.5 1.131 0.123
7 50 3 0.972 -0.028
7 50 4.5 0.898 -0.108
7 50 6 0.754 -0.282
7 50 7.5 0.735 -0.308
9 50 0 1.1311 0.123
9 50 1.5 1.185 0.170
9 50 3 0.923 -0.080
9 50 4.5 0.875 -0.134
9 50 6 0.779 -0.250
9 50 7.5 0.722 -0.326
Kinetic analysis
  pH=4 pH=7 pH=9
Intercept 0.317 0.229 0.249
gradient -0.099 -0.077 -0.082
standard error of gradient 0.003 0.006 0.008
half-life [hr] 7 9 8.5
r^2 0.996 0.978 0.959
Test II
pH Temperature Tiime conc. [mg/l] ln(conc.)
4 36 0 1.193 0.176
4 36 2 1.082 0.079
4 36 4 1.015 0.015
4 36 21 0.669 -0.402
4 36 23.5 0.604 -0.504
7 36 0 1.194 0.177
7 36 2 1.067 0.065
7 36 4 1.026 0.026
7 36 21 0.65 -0.431
7 36 23.5 0.616 -0.485
9 36 0 1.153 0.142
9 36 2 1.111 0.105
9 36 4 1.057 0.055
9 36 21 0.729 -0.316
9 36 23.5 0.712 -0.340
Kinetic analysis
  pH=4 pH=7 pH=9
Intercept 0.147 0.143 0.141
gradient -0.0272 -0.0265 -0.0205
standard error of gradient 0.0012 0.0013 0.0009
half-life [hr] 25.6 26.2 33.8
r^2 0.994 0.993 0.995
Conclusions:
The rates of hydrolysis measured allowed the calculation of the half-life at 25°C:
pH 4 : 116 hours
pH 7 : 86 hours
pH 9 : 171 hours

Within the limits of the exptrapolation, these results are typical of epoxy containing compounds.
Executive summary:

The rate of hydrolysis of EPIKOTE 828 has been measured at the three pH values (4, 7, 9) and two temperatures (38°C, 50°C). Analysis of the content of the main component was performed by high performance liquid chromatography, using direct injection of the aqueous samples. All the tests showed a decline in the concentration of the test substance according to first-order kinetics.

The extrapolated half lives at pH 4, 7 and 9 were typical of epoxy compounds. Regression of the six data points, expressed as log (half life) and reciprocal temperature, gave an overall half life of 117 hours at 25°C, assuming the rate to be independent of pH, which is known to be a reasonable assumption.

Description of key information

half-life 117 h at 25°C (OECD 111)

Key value for chemical safety assessment

Half-life for hydrolysis:
117 h
at the temperature of:
25 °C

Additional information