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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
18 February 1987 to 31 March 1987
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: EC guideline No L 251 / C.10
Deviations:
not specified
GLP compliance:
yes
Specific details on test material used for the study:
Product designation: Monoazo Yellow TZ 2382
Identification: FAT 40'224/C
Vers. 10/86 Op. 1/86
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
After reaction time, 10.0 mL of the test solution is neutralized and diluted with water to 100 mL.
Buffers:
pH 4.0 = 5.10 g of potassium biphtalate diluted to 500 mL with water.
pH 7.0 = 14.5 mL of 1 N NaOH + 3.40 g of monopotassium phosphate diluted to 500 mL with water.
pH 9.0 = 10.5 mL of 1 N NaOH + 1.54 g of boric acid + 1.86 g of KCl diluted to 500 mL with water.

The buffer solutions are heated before use for 15 minutes at 121 °C for sterilisation purposes.

Details on test conditions:
- About 250 mg Monoazo Yellow TZ 2382 is accurately weighted into a 250 mL volumetric flask.
- The test substance is dissolved in and diluted to 250 mL with the buffer solution (pH 4, pH 7 and pH 9 for the preliminary test, pH 4 and pH 9 for the test 1 and 3).
- The hydrolysis reaction is carried out in a thermostatically controlled water bath.
- After reaction time 10 mL of test solution is diluted to 100 mL. This solution is measured according to the method AAK 10/87.
- only brown glass reaction flasks are used to exclude photolytic effects.
Duration:
20 h
pH:
4
Temp.:
50
Initial conc. measured:
1.02 g/L
Duration:
57
pH:
4
Temp.:
39
Initial conc. measured:
1.02 g/L
Duration:
40
pH:
9
Temp.:
50
Initial conc. measured:
1 g/L
Duration:
266 h
pH:
9
Temp.:
39
Initial conc. measured:
1 g/L
Number of replicates:
at pH 4: 2 replicates
at pH 9: 2 replicates
Positive controls:
no
Negative controls:
no
Statistical methods:
The constant k, at 25 °C, is calculated using the values of Kobs, at 50 °C and 39 °C (Arrhenius relation).


Preliminary study:
pH 4 initial concentration (average): 1.00 g/L at 50 °C, final concentration: 0.02 g/L
pH 7 initial concentration (average): 1.03 g/L at 50 °C, final concentration: 0.93 g/L
pH 9 initial concentration (average): 1.00 g/L at 50 °C, final concentration: 0.16 g/L
Transformation products:
not measured
pH:
4
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
17.8 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r^2=0,999
pH:
4
Temp.:
39 °C
Hydrolysis rate constant:
0 s-1
DT50:
44.3 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r^2=0,9999
pH:
9
Temp.:
50 °C
Hydrolysis rate constant:
0 s-1
DT50:
43 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r^2=0,9981
pH:
9
Temp.:
39 °C
Hydrolysis rate constant:
0 s-1
DT50:
206.7 h
Type:
(pseudo-)first order (= half-life)
Remarks on result:
other: r^2=0,9993
Details on results:
no data

At 50 °C the hydrolysis of Monoazo Yellow TZ 2382 is lower than 10 % at pH 7 and greater than 10 % at pH 4 and 9.


Hence, the hydrolysis is examined at pH 4 and 9. To be sure that the hydrolysis is lower than 10 % at pH 7 the test was repeated. The result thereof is 6.6 %.

Validity criteria fulfilled:
yes
Conclusions:
FAT 40224/C is hydrolytically stable.
Executive summary:

A hydrolysis study was performed with FAT 40224/C, following the EC C.10 guideline. No positive or negative control was performed. The test substance is stable at pH 7 at 50 °C: it has a half-life time longer than one year at pH 7 at 25 °C. Half-life time of the test substance at pH 4 at 25 °C = 157 h. Half-life time of the test substance at pH 9 at 25 °C = 1816 h. Based on the test results, FAT 40224/C is hydrolytically stable.

Description of key information

A hydrolysis study was performed with FAT 40224/C, following the EC C.10 guideline. No positive or negative control was performed. The test substance is stable at pH 7 at 50 °C: it has a half-life time longer than one year at pH 7 at 25 °C. Half-life time of the test substance at pH 4 at 25 °C = 157 h. Half-life time of the test substance at pH 9 at 25 °C = 1816 h. Based on the test results, FAT 40224/C is hydrolytically stable.

Key value for chemical safety assessment

Half-life for hydrolysis:
1 816 h
at the temperature of:
25 °C

Additional information

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