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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From July 4, 2014 to May 5, 2015
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
GLP compliance:
no
Remarks:
conducted at the company internal.
Analytical monitoring:
yes
Remarks:
Digital Electronic Indictors + S.S.R. with PID automatic calculation capability
Buffers:
- Acetate buffer pH 4, 0.1 M: solution of 0.1 M acetic acid adjusted to pH 4 using 10 N sodium hydroxide. The buffer contains 0.002% (w/v) PREVENTAL BIT 20.
- Phosphate buffer pH 7, 0.1 M: solution of 0.1 M potassium dihydrogenphosphate adjusted to pH 7 using 10 N sodium hydroxide. The buffer contains 0.002% (w/v) PREVENTAL BIT 20.
- Borate buffer pH 9, 0.1 M: solution of 0.1 M boric acid and 0.1 M potassium chloride adjusted to pH 9 using 10 N sodium hydroxide. The buffer contains 0.002% (w/v) PREVENTAL BIT 20.
Number of replicates:
two
Statistical methods:
System control, data acquisition and data processing were performed using the following programme: Empower version 5.00 (Waters, Milford, MA, USA)
Preliminary study:
At pH 4 a degree of hydrolysis of ≥ 40% after 5 days was observed. The mean recovery of the buffer solutions at pH 9 at t=0 was non detected and was therefore outside the criterion range of 90-110%. Because multiple degradation products were observed at pH 4 and pH 7 and pH 9 and no test substance was detected in the test samples (i.e. a degree of hydrolysis of ≥ 10% ) after 5 days it was decided that the higher Tier test was required to determine the half-life time of the test substance.
Transformation products:
no
% Recovery:
99.3
pH:
4
Temp.:
50 °C
Duration:
0 h
% Recovery:
82.4
pH:
7
Temp.:
50 °C
Duration:
0 h
pH:
9
Temp.:
50 °C
Duration:
0 h
Remarks on result:
not determinable
Remarks:
The low recoveries are probably caused by unstable at pH 9 .
pH:
4
Temp.:
25 °C
Hydrolysis rate constant:
0 h-1
DT50:
173 d
Type:
(pseudo-)first order (= half-life)
pH:
7
Temp.:
25 °C
Hydrolysis rate constant:
1.06 h-1
DT50:
39.3 min
Type:
(pseudo-)first order (= half-life)
pH:
9
Remarks on result:
not determinable

Table 1. Preliminary test-hydrolysis of the test substance at pH 4, pH 7 and pH 9

pH code

Sampling time

Analysed concentration

(mg/l)

Degree of hydrolysis

(%)

Actual pH

Individual

Mean

pH 4

0 hours

99.3

3.90

101

3.90

5 days

45.5

55.7

57.5

3.90

41.1

59.6

3.90

pH 7

0 hours

107

7.10

107

7.10

5 days

N.D.

N.D.

N.D.

7.10

N.D.

N.D.

7.10

pH 9

0 hours

N.D.

9.00

N.D.

9.00

5 days

N.D.

N.D.

N.D.

8.95

N.D.

N.D.

8.95

N.D. means non detected.

 

Table 2. Preliminary test-Recoveries

pH code

Nominal concentration

(mg/l)

Analysed concentration

(mg/l)

Recovery

(%)

Mean recovery

(%)

pH 4

309

305

98.6

99.3

309

309

100

pH 7

107

101

94.3

82.4

107

75.4

70.5

pH 9

115

N.D.

N.D.

N.D.

115

N.D.

N.D.

N.D. means non detected.

 

Table 3. Rate constants (kobs) and half-life time (t½) at pH 4 and pH 7

Temperature

(°C)

kobs(hours-1)

t½

pH 4

pH 7

pH 4

pH 7

20

1.03× 10-4

8.31× 10-1

280 days

50.0 mins

25

1.67× 10-4

1.06

173 days

39.3 mins

40

6.43× 10-4

2.09

44.9 days

19.9 mins

50

4.61× 10-2

2.11

15.0 days

19.7 mins

 

Validity criteria fulfilled:
yes
Conclusions:
According to OECD 111 and EC C.7 test method, the rate constant (kobs) of Everzol Red CDN Crude at 25°C are 1.67 × 10-4 and 1.06 hour-1 respectively at pH=4 and pH=7. And the half-life time of Everzol Red CDN Crude at 25°C are 173 days and 39.3 mins respectively at pH=4 and pH=7.
Executive summary:

This test using the procedures outlined in the Everlight Study Plan for 140623-11, OECD 111 (OECD, 2004) and EC C.7 (EC no. 440/2008).

In the preliminary test, the multiple degradation products were observed at pH=4 and pH=7 and pH=9 and no test substance was detected in the test samples (i.e. a degree of hydrolysis of ≥ 10 % ) after 5 days it was decided that the higher Tier test was required to determine the half-life time of the test substance. In main study,the mean recoveries of the buffer solutions at pH=4 and t=0 fell within the criterion range of 90-110 %. It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance. At pH=7, the mean recoveries of the buffer solutions at t=0 fell within the criterion range of 70-110 %. Analysis of different waiting times cause two samples at the same time have 20-30 % difference. At pH=9, the mean recovery of the buffer solutions at t=0 was non detected and was therefore outside the criterion range of 90-110 %. The low recoveries are probably caused by unstable at pH=9. For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. At all temperatures linear relationships were obtained. The half-life times of the test substance were determined according to the model for pseudo-first order reactions. All logarithms of the relative concentrations were correlated with time using linear regression analysis. The rate constant (kobs) and half-life time of the test substance at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C.Therefore, the rate constant (kobs) of Everzol Red CDN Crude at 25°C are 1.67× 10-4 and 1.06 hour-1 respectivelyat pH=4 and pH =7. And the half-life time of Everzol Red CDN Crude at 25°C are 173 days and 39.3 mins respectively at pH=4 and pH=7.

Description of key information

The rate constant (kobs) of Everzol Red CDN Crude at25°C are 1.67× 10-4 and 1.06 hour-1 respectivelyat pH=4 and pH=7. And the half-life timeof Everzol Red CDN Crude at25°C are 173 days and 39.3 mins respectively at pH=4 and pH=7(OECD TG111).

Key value for chemical safety assessment

Additional information

In the preliminary test, the multiple degradation products were observed at pH=4 and pH=7 and pH=9 and no test substance was detected in the test samples (i.e. a degree of hydrolysis of ≥ 10% ) after 5 days it was decided that the higher Tier test was required to determine the half-life time of the test substance.In Main study,the mean recoveries of the buffer solutions at pH=4 and t=0 fell within the criterion range of 90-110% . It demonstrated that the analytical method was adequate to support the hydrolysis study on the test substance. At pH=7, the mean recoveries of the buffer solutions at t=0 fell within the criterion range of 70-110%. Analysis of different waiting times cause two samples at the same time have 20-30% difference. At pH=9, the mean recovery of the buffer solutions at t=0 was non detected and was therefore outside the criterion range of 90-110%. The low recoveries are probably caused by unstable at pH=9. For testing of pseudo-first order kinetics the mean logarithms of the relative concentrations between 10% and 90% were plotted against time. At all temperatures linear relationships were obtained. The half-life times of the test substance were determined according to the model for pseudo-first order reactions. All logarithms of the relative concentrations were correlated with time using linear regression analysis. The rate constant (kobs) and half-life time of the test substance at each temperature was obtained and the Arrhenius equation was used to determine the rate constant and half-life time at 25°C. Therefore, the rate constant (kobs) of Everzol Red CDN Crude at 25°C are 1.67× 10-4 and 1.06 hour-1 respectivelyat pH=4 and pH=7. And the half-life time of Everzol Red CDN Crude at 25°C are 173 days and 39.3 mins respectively at pH=4 and pH=7.