[No public or meaningful name is available]

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

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 (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: MH-12/2014 (China)
- Expiration date of the lot/batch: 13 November 2019

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Frozen in the dark

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The sample solutions were taken from the waterbath at various times and the pH of each solution recorded. The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).

Buffers:

The test system used sterile buffer solutions at pH’s 4, 7 and 9.

Details on test conditions:

Performance of the Test
Preparation of the Test Solutions
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 7 g/L (Preliminary Test), or 1 g/L (Tier 2) in the relevant buffer solutions. The concentration of each solution did not exceed the lesser of 0.01 mol/L or half the water solubility. The test solutions were split into individual vessels for each data point. The solutions were shielded from light whilst maintained at the test temperature.

Preliminary Test
Sample solutions were prepared at a nominal concentration of 7 g/L at pH 4, 7 and 9 and maintained at 50.0 ± 0.5 °C for a period of 120 hours.

Tier 2
Results from the Preliminary Test showed it was necessary to undertake further testing at pH 7, with solutions (prepared at a nominal concentration of 1 g/L) being maintained at 40.0 ± 0.5 °C, 50.0 ± 0.5 °C and 60.0 ± 0.5 °C for a period of 24, 3.5 and 1.75 hours respectively, further testing at pH 9, with solutions being maintained at 10.0 ± 0.5 °C, 20.0 ± 0.5 °C and 30.0 ± 0.5 °C for a period of 24, 3.5 and 1 hours respectively.

Calculation
The response factors of the standard peak areas (unit peak area per mg/L) were calculated using the following equation.

RF = Rstd / Cstd

where:
RF = response factor for the standard solution
RSTD = peak area for the standard solution
CSTD = concentration for the standard solution (mg/L)

The sample solution (g/L) was calculated using the following equation.

C = (Rspl / RFstd) x (D / 1.00E+03)

where:
C = sample solution concentration (g/L)
RSPL = mean peak area for the sample solution
RFSTD = mean response factor for the standard solutions (unit peak area per mg/L)
D = dilution factor (10)

Calculation of the Degree of Hydrolysis
The decrease in concentration (preliminary test) or the degree of hydrolysis was calculated using the following equation:

Degree of hydrolysis in % = [ (C0 - Ct) / C0 ] · 100

where:
C0 = concentration of time 0
Ct = concentration of time t

Testing the Reaction for Pseudo First Order
The general rate expression for a first order reaction is:

d(c) / dt = - k · c

or in the integrated form

-1n (C0 - Ct) = -k · t

or

ln ct = (-k) · t – ln c0
(equation of a linear function)

Therefore, the rate constant k is the slope of a plot of ln ct versus t. The data were plotted as ln ct versus t. The linear plots prove that the hydrolysis reaction is pseudo first order. The reaction rate constant k can be calculated by regression analysis or the following equation.

-k = (1 / t) · 1n (C0 / Ct)

The half-life was calculated from the following equation:

t½ = 0.693/k

where:
c0 = Concentration of the test solution at time 0 [µg/mL]
ct = Concentration of the test solution at time t [µg/mL]
k = First order rate constant [hours-1]
t1/2 = Half-life [hours]

Evaluation of k at 25 °C
When the rate constants are known for two temperatures the rate constants at other temperatures can be calculated using the Arrhenius equation:

k = A ·e-(E / R·T)

or

1n k = -(E / R) ·1 / T) + 1n A

A plot of ln k versus 1/T gives a straight line with a slope of -E/R.

where:
k = Rate constant, measured at different temperatures
E = Activation energy [kJ/mol]
T = Absolute temperature [K]
R = Gas constant [8.314 J/mol K]
A = Pre-exponential factor

The half-life at 25 °C was interpolated/extrapolated directly from the graph.

Duration:

120 h

Temp.:

50 °C

Initial conc. measured:

7 g/L

Duration:

24 h

pH:

7

Temp.:

40 °C

Initial conc. measured:

1 g/L

Duration:

3.5 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

1 g/L

Duration:

1.75 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

1 g/L

Duration:

24 h

pH:

9

Initial conc. measured:

1 g/L

Duration:

3.5 h

pH:

9

Initial conc. measured:

1 g/L

Duration:

1 h

pH:

9

Initial conc. measured:

1 g/L

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Statistical methods:

No data

Preliminary study:

Preliminary pH 4 Test at 50.0 ± 0.5 ºC
Less than 10 % hydrolysis after 5 days at 50.0 ± 0.5 °C, equivalent to a half-life greater than 1 year at 25 °C.

Preliminary pH 7 Test at 50.0 ± 0.5 ºC
During the Preliminary test at pH 7 (50.0 ± 0.5 °C) there was an instability of pH causing the pH to drop to approximately pH 4, providing a plateau in the hydrolysis results. The Tier 2 test was carried out at a lower concentration with a higher buffer concentration to reduce this effect. The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 40 ± 0.5 °C, 50 ± 0.5 °C and 60 ± 0.5 °C, were required to estimate the rate constant and half-life at 25 °C.

Preliminary pH 9 Test at 50.0 ± 0.5 ºC
During the Preliminary test at pH 9 (50.0 ± 0.5 °C) there was an instability of pH causing the pH to drop to approximately pH 4, providing a plateau in the hydrolysis results. The Tier 2 test was carried out at a lower concentration with a higher buffer concentration to reduce this effect. The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 10 ± 0.5 °C, 20 ± 0.5 °C and 30 ± 0.5 °C, were required to estimate the rate constant and half-life at 25 °C.

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

None

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

44.4 h

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

0.934 h

Details on results:

pH 7 Test at 40.0 ± 0.5 ºC - Tier 2
N.B. The 24 hour samples indicated less than 10 % hydrolysis and are therefore not included in the statistics.

Slope = -5.17E-02
kobs = 0.119 hour-1
= 3.30E-05 second-1
t½ = 5.83 hours

pH 7 Test at 50.0 ± 0.5 ºC - Tier 2
Slope = -0.186
kobs = 0.429 hour-1
= 1.19E-04 second-1
t½ = 1.62 hours

pH 7 Test at 60.0 ± 0.5 ºC - Tier 2
Slope = -0.588
kobs = 1.36 hour-1
= 3.76E-04 second-1
t½ = 0.512 hours

pH 9 Test at 10.0 ± 0.5 ºC - Tier 2
Slope = -3.90E-02
kobs = 8.99E-02 hour-1
= 2.50E-05 second-1
t½ = 7.71 hours

pH 9 Test at 20.0 ± 0.5 ºC - Tier 2
Slope = -0.165
kobs = 0.381 hour-1
= 1.06E-04 second-1
t½ = 1.82 hours

pH 9 Test at 30.0 ± 0.5 ºC - Tier 2
Slope = -0.618
kobs = 1.42 hour-1
= 3.95E-04 second-1
t½ = 0.487 hours

pH 7 Arrhenius Data
From the graph of the data, the rate constant and half-life at 25 °C have been estimated to be as follows:
kobs = 1.56E-02 hour-1
= 4.34E-06 second-1
t½ = 44.4 hours
= 1.85 days

pH 9 Arrhenius Data
From the graph of the data, the rate constant and half-life at 25 °C have been estimated to be as follows:
kobs = 0.742 hour-1
= 2.06E-04 second-1
t½ = 0.934 hours

Tier 2

The mean peak areas relating to the standard and sample solutions are shown in the following tables:

pH 7 - 40.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 102 mg/L	1.3654 x 10^7
Standard 107 mg/L	1.4406 x 10^7
Initial Sample A, pH 7	1.3780 x 10^7
Initial Sample B, pH 7	1.3749 x 10^7
2.0 Hour Sample A, pH 7	1.0907 x 10^7
2.0 Hour Sample B, pH 7	1.1013 x 10^7
2.5 Hour Sample A, pH 7	1.0396 x 10^7
2.5 Hour Sample B, pH 7	1.0101 x 10^7
3.0 Hour Sample A, pH 7	9.7303 x 10^6
3.0 Hour Sample B, pH 7	9.7217 x 10^6
3.5 Hour Sample A, pH 7	7.0607 x 10^6
3.5 Hour Sample B, pH 7	9.1666 x 10^6
4.0 Hour Sample A, pH 7	8.6521 x 10^6
4.0 Hour Sample B, pH 7	8.5190 x 10^6
5.0 Hour Sample A, pH 7	7.6421 x 10^6
5.0 Hour Sample B, pH 7	7.7125 x 10^6
6.0 Hour Sample A, pH 7	6.7872 x 10^6
6.0 Hour Sample B, pH 7	6.8221 x 10^6
Standard 104 mg/L	1.4074 x 10^7
Standard 104 mg/L	1.3432 x 10^7
24.0 Hour Sample A, pH 7	9.6379 x 10^5
24.0 Hour Sample B, pH 7	9.4856 x 10^5

 

pH 7 - 50.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 103 mg/L	1.3881 x 10^7
Standard 102 mg/L	1.3744 x 10^7
Initial Sample A, pH 7	1.4167 x 10^7
0.5 Hour Sample A, pH 7	1.1660 x 10^7
1.0 Hour Sample A, pH 7	9.1570 x 10^6
1.5 Hour Sample A, pH 7	7.7388 x 10^6
2.0 Hour Sample A, pH 7	6.0489 x 10^6
2.5 Hour Sample A, pH 7	4.2968 x 10^6
3.0 Hour Sample A, pH 7	4.0360 x 10^6
3.5 Hour Sample A, pH 7	3.1537 x 10^6
Standard 103 mg/L	1.3858 x 10^7
Standard 102 mg/L	1.3703 x 10^7
Initial Sample B, pH 7	1.4072 x 10^7
0.5 Hour Sample B, pH 7	1.1129 x 10^7
1.0 Hour Sample B, pH 7	8.9992 x 10^6
1.5 Hour Sample B, pH 7	7.0426 x 10^6
2.0 Hour Sample B, pH 7	5.7150 x 10^6
2.5 Hour Sample B, pH 7	4.8178 x 10^6
3.0 Hour Sample B, pH 7	3.9012 x 10^6
3.5 Hour Sample B, pH 7	3.1857 x 10^6

pH 7 - 60.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 105 mg/L	1.4335 x 10^7
Standard 105 mg/L	1.4499 x 10^7
Initial Sample A, pH 7	1.3923 x 10^7
Initial Sample B, pH 7	1.4030 x 10^7
0.25 Hour Sample A, pH 7	1.0042 x 10^7
0.25 Hour Sample B, pH 7	1.0084 x 10^7
0.5 Hour Sample A, pH 7	7.4774 x 10^6
0.5 Hour Sample B, pH 7	7.2293 x 10^6
0.75 Hour Sample A, pH 7	4.9115 x 10^6
0.75 Hour Sample B, pH 7	5.0567 x 10^6
1.00 Hour Sample A, pH 7	3.6499 x 10^6
1.00 Hour Sample B, pH 7	3.7387 x 10^6
1.25 Hour Sample A, pH 7	2.6039 x 10^6
1.25 Hour Sample B, pH 7	2.9199 x 10^6
1.5 Hour Sample A, pH 7	1.7630 x 10^6
1.5 Hour Sample B, pH 7	1.7165 x 10^6
1.75 Hour Sample A, pH 7	1.3658 x 10^6
1.75 Hour Sample B, pH 7	1.3066 x 10^6

 

pH 9 - 10.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 103 mg/L	1.3020 x 10^7
Standard 104 mg/L	1.4321 x 10^7
Initial Sample A, pH 9	1.3392 x 10^7
Initial Sample B, pH 9	1.2491 x 10^7
1.0 Hour Sample A, pH 9	1.1666 x 10^7
1.0 Hour Sample B, pH 9	1.2046 x 10^7
2.0 Hour Sample A, pH 9	1.0612 x 10^7
2.0 Hour Sample B, pH 9	1.0766 x 10^7
3.0 Hour Sample A, pH 9	9.7681 x 10^6
3.0 Hour Sample B, pH 9	9.7669 x 10^6
4.0 Hour Sample A, pH 9	8.9954 x 10^6
4.0 Hour Sample B, pH 9	8.6560 x 10^6
5.0 Hour Sample A, pH 9	7.8111 x 10^6
5.0 Hour Sample B, pH 9	8.1407 x 10^6
6.0 Hour Sample A, pH 9	7.2337 x 10^6
6.0 Hour Sample B, pH 9	7.4981 x 10^6
Standard 105 mg/L	1.4363 x 10^7
Standard 102 mg/L	1.3937 x 10^7
24.0 Hour Sample A, pH 9	1.5277 x 10^6
24.0 Hour Sample B, pH 9	1.5452 x 10^6

 

pH 9 - 20.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 103 mg/L	1.3020 x 10^7
Standard 104 mg/L	1.4321 x 10^7
Initial Sample A, pH 9	1.3392 x 10^7
Initial Sample B, pH 9	1.2491 x 10^7
0.5 Hour Sample A, pH 9	1.1032 x 10^7
0.5 Hour Sample B, pH 9	1.0868 x 10^7
1.0 Hour Sample A, pH 9	8.7474 x 10^6
1.0 Hour Sample B, pH 9	8.8671 x 10^6
1.5 Hour Sample A, pH 9	7.5113 x 10^6
1.5 Hour Sample B, pH 9	7.3794 x 10^6
2.0 Hour Sample A, pH 9	5.8502 x 10^6
2.0 Hour Sample B, pH 9	5.9626 x 10^6
2.5 Hour Sample A, pH 9	5.2187 x 10^6
2.5 Hour Sample B, pH 9	4.9937 x 10^6
3.0 Hour Sample A, pH 9	4.0597 x 10^6
3.0 Hour Sample B, pH 9	4.0501 x 10^6
3.5 Hour Sample A, pH 9	3.4949 x 10^6
3.5 Hour Sample B, pH 9	3.4925 x 10^6

 

pH 9 - 30.0 ± 0.5 °C Tier 2 Testing

Solution	Mean Peak Area
Standard 101 mg/L	1.3498 x 10^7
Standard 104 mg/L	1.3912 x 10^7
Initial Sample A, pH 9	1.0594 x 10^7
Initial Sample B, pH 9	1.0458 x 10^6
0.08 Hour Sample A, pH 9	9.5097 x 10^6
0.08 Hour Sample B, pH 9	9.1754 x 10^6
0.17 Hour Sample A, pH 9	7.1215 x 10^6
0.17 Hour Sample B, pH 9	8.4110 x 10^6
0.25 Hour Sample A, pH 9	7.4856 x 10^6
0.25 Hour Sample B, pH 9	7.3957 x 10^6
0.33 Hour Sample A, pH 9	6.5182 x 10^6
0.33 Hour Sample B, pH 9	5.8680 x 10^6
0.42 Hour Sample A, pH 9	5.6080 x 10^6
0.42 Hour Sample B, pH 9	5.7774 x 10^6
0.50 Hour Sample A, pH 9	5.1638 x 10^6
0.50 Hour Sample B, pH 9	4.8960 x 10^6
0.75 Hour Sample A, pH 9	3.6562 x 10^6
0.75 Hour Sample B, pH 9	3.5909 x 10^6
1.00 Hour Sample A, pH 9	2.5133 x 10^6
1.00 Hour Sample B, pH 9	2.4386 x 10^6

 

The test item concentrations at the given time points are shown in the following tables:

pH 7 Test at 40.0 ± 0.5 ºC - Tier 2

Time (Hours)	Concentration (g/L)	Log10 concentration (g/L)	% mean initial concentration
0 (A)	1.02	7.88 x 10^-3	-
0 (B)	1.02	6.92 x 10^-3	-
2.0 (A)	0.806	-9.37 x 10^-2	79.2
2.0 (B)	0.814	-8.94 x 10^-2	80.0
2.5 (A)	0.768	-0.114	75.5
2.5 (B)	0.746	-0.127	73.4
3.0 (A)	0.719	-0.143	70.7
3.0 (B)	0.718	-0.144	70.6
3.5 (A)	0.522	-0.283	51.3
3.5 (B)	0.677	-0.169	66.6
4.0 (A)	0.639	-0.194	62.9
4.0 (B)	0.630	-0.201	61.9
5.0 (A)	0.565	-0.248	55.5
5.0 (B)	0.570	-0.244	56.0
6.0 (A)	0.502	-0.300	49.3
6.0 (B)	0.504	-0.297	49.6
24.0 (A)	7.30 x 10^-2	-1.14	7.18
24.0 (B)	7.19 x 10^-2	-1.14	7.07

pH 7 Test at 50.0 ± 0.5 ºC - Tier 2

Time (Hours)	Concentration (g/L)	Log10 concentration (g/L)	% mean initial concentration
0 (A)	1.05	2.13 x 10^-2	-
0 (B)	1.05	1.94 x 10^-2	-
0.5 (A)	0.864	-6.33 x 10^-2	82.5
0.5 (B)	0.827	-8.25 x 10^-2	78.9
1.0 (A)	0.679	-0.168	64.8
1.0 (B)	0.669	-0.175	63.8
1.5 (A)	0.574	-0.241	54.7
1.5 (B)	0.523	-0.281	49.9
2.0 (A)	0.448	-0.348	42.8
2.0 (B)	0.425	-0.372	40.5
2.5 (A)	0.319	-0.497	30.4
2.5 (B)	0.358	-0.446	34.2
3.0 (A)	0.299	-0.524	28.6
3.0 (B)	0.290	-0.538	27.7
3.5 (A)	0.234	-0.631	22.3
3.5 (B)	0.237	-0.626

Validity criteria fulfilled:

yes

Conclusions:

The estimated rate constant and half-lives at 25 °C of the test item are:
At pH 4 the estimated half-life at 25 °C was >1 year.
At pH 7 the estimated rate constant was 4.34E-06 s-1 at 25 °C with an estimated half-life of 44.4 hours.
At pH 9 the estimated rate constant was 2.06E-04 s-1 at 25 °C with an estimated half-life of 0.934 hours.

Executive summary:

The hydrolysis behavior as a function of pH of FAT 40069/DTE has been evaluated according to OECD Guideline 111 and EU Method C.7.

During the Preliminary test at pH 7 (50.0 ± 0.5 °C) there was an instability of pH causing the pH to drop to approximately pH 4, providing a plateau in the hydrolysis results. The Tier 2 test was carried out at a lower concentration with a higher buffer concentration to reduce this effect. The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 40 ± 0.5°C, 50 ± 0.5°C and 60 ± 0.5 °C, were required to estimate the rate constant and half-life at 25 °C. The results are summarized below:

pH	Estimated rate constant (s^-1) at 25 °C	Estimated half-life at 25 °C
4	-	>1 year
7	4.34 x 10^-6	44.4 hours
9	2.06 x 10^-4	0.934 hours

 

 

Description of key information

The test substance FAT 40069 has been determined to be hydrolytically stable, i.e. a half-life of greater than 1 year at 25 °C at pH 4, 44.4 hours at pH 7 and 0.934 hours at pH 9.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

25 °C

Additional information

The hydrolysis behaviour as a function of pH of test substance FAT 40069/DTE has been evaluated according to OECD Guideline 111 and EU Method C.7. During the Preliminary test at pH 7 (50.0 ± 0.5 °C) there was an instability of pH causing the pH to drop to approximately pH 4, providing a plateau in the hydrolysis results. The Tier 2 test was carried out at a lower concentration with a higher buffer concentration to reduce this effect. The extent of hydrolysis after 120 hours indicated that further tests (Tier 2), conducted at 40 ± 0.5 °C, 50 ± 0.5 °C and 60 ± 0.5 °C, were required to estimate the rate constant and half-life at 25 °C.

The results are summarized below:

pH	Estimated rate constant (s^-1) at 25 °C	Estimated half-life at 25 °C
4	-	>1 year
7	4.34 x 10^-6	44.4 hours
9	2.06 x 10^-4	0.934 hours