Cuprate(6-), [2-[[[[3-[[4-chloro-6-[[4-[[4-chloro-6-[(3-sulfophenyl)amino]-1,3,5-triazin-2-yl]amino]-2,5-disulfophenyl]amino]-1,3,5-triazin-2-yl]amino]-2-hydroxy-5-sulfophenyl]azo]phenylmethyl]azo]-5-sulfobenzoato(8-)]-, pentasodium hydrogen, (SP-4-3)-

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2019-08-01 to 2020-04-28

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)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

440/2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Samples were taken at test start (0 h) and at 6-10 spaced time points, normally between 10 and at least 90% of hydrolysis (2 half lives), at each test temperature. After sampling, 100 µL of the sample were diluted with 0.9 mL acetonitrile : methanol : purified water : buffer solution pH 5 (30 : 20 : 37.5 : 12.5), corresponding to a dilution factor of 10, and analyzed.
All test item containing samples were analyzed immediately (if possible less than 30 min until start of analyses, but at least not more than 2.5% of the total study time).

Buffers:

Test Systems Sterile buffer solutions with pH values 4, 7 and 9

Buffer solutions were prepared from chemicals with analytical grade or better quality following the composition guidance given in “KÜSTER-THIEL, Rechentafeln für die Chemische Analytik” and the OECD Guideline No. 111, respectively, by direct weighing of the buffer components (nominal values are given below). Buffers were purged with nitrogen for 5 min and then the pH was checked to a precision of at least 0.1 at the test temperatures. Buffers were sterilized by filtration through 0.2 µm.

Buffer solution pH 4 0.18 g of sodium hydroxide and 5.7555 g of mono potassium citrate were dissolved in 500 mL ultrapure water.

Buffer solution pH 7 3.854 g of ammonium acetate were dissolved in 500 mL ultrapure water.

Buffer solution pH 9 0.426 g sodium hydroxide, 1.8638 g potassium chloride and 1.5458 g boric acid were dissolved in 500 mL ultrapure water.

Reason for the selection The buffer systems were suitable for their pH values.

Chemical Origin Batch number Purity [%]
NaOH VWR 17F284110 ≥ 97
19F204136 99.3
H3BO3 ROTH 028261978 ≥ 99.5
KCl ROTH 079279869 ≥ 99.5
Ammonium acetate VWR 18C204114 99.2
19D044130 98.1
KH2 Citrate SIGMA-ALDRICH BCBW9888 ≥ 98
Ultrapure water MERCK In-house device

Details on test conditions:

Preliminary test: pH 4, 7 and 9 at 50 °C for 120 h
Devinitive test: pH 4, 7 and 9 at 20, 30 and 50 °C, respectively

Duration:

767 h

pH:

4

Temp.:

20 °C

Initial conc. measured:

7.95 g/L

Remarks:

10 samplings

Duration:

767 h

pH:

4

Temp.:

30 °C

Initial conc. measured:

7.95 g/L

Remarks:

10 samplings

Duration:

768 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

7.95 g/L

Remarks:

10 samplings

Duration:

313 h

pH:

7

Temp.:

20 °C

Initial conc. measured:

7.59 g/L

Remarks:

6 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Duration:

314 h

pH:

7

Temp.:

30 °C

Initial conc. measured:

7.59 g/L

Remarks:

6 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Duration:

266 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

7.59 g/L

Remarks:

5 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Duration:

314 h

pH:

9

Temp.:

20 °C

Initial conc. measured:

7.65 g/L

Remarks:

6 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Duration:

314 h

pH:

9

Temp.:

30 °C

Initial conc. measured:

7.65 g/L

Remarks:

6 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Duration:

315 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

7.65 g/L

Remarks:

6 samplings; stopped due to stability after 120 h at 50 °C (criterion for performing the definitive test)

Number of replicates:

Duplicates per pH and sampling date, single injections.
A third replicate was prepared and immediately frozen after sampling for analyses of possible transformation products.

Positive controls:

no

Negative controls:

yes

Remarks:

Buffer solutions (pH value 4, 7 and 9)

Preliminary study:

The preliminary test was conducted with a test item concentration of 1.5 g/L in buffer solutions at pH 4, 7 and 9 at 50 °C. For all pH values the definitive test was performed, as a significant reduction (> 10%) of the test item concentration was observed in the preliminary test (50.8% for pH 4, 25.7% for pH 7 and 21.5% for pH 9).

Test performance:

The definitive test was conducted with a test item concentration of 7.5 g/L in buffer solutions at pH 4, 7 and 9 at temperatures of 20, 30 and 50 °C. Samples were taken at test start (0 h) and at 6-10 spaced time points until test end. Pure test system (buffer solution at the respective pH value) was analyzed at test start and test end and there was no analytical interference with the test item.

Transformation products:

yes

No.:

#1

No.:

#2

No.:

#3

No.:

#4

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

Hydrolysis:
The test item showed a slow hydrolysis rate (> 30 d) for pH 4 at 20 and 30 °C and a moderate hydrolysis (2.4 h ≤ t1/2 ≤ 30 d) for pH 4 at 50 °C.

At pH 7 and 9 no significant reduction of the test item concentration was observed after 266 h at pH 7 and 315 h at pH 9 at 50 °C. Therefore, the definitive study at pH 7 and 9 was stopped and the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.


Transformation products:
During LC-DAD analysis one (major) transformation product was observed. This transformation product (#3) could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI+ ionisation.

At 50 °C three additional (minor) transformation products (#1, #2, #4) were observed during LC-DAD analysis. At 20 and 30 °C only the transformation product #2 was additionally observed. These minor transformation products also could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI+ ionisation.

Key result

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

0 s-1

DT50:

1 077 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

4

Temp.:

30 °C

Hydrolysis rate constant:

0 s-1

DT50:

880 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0 s-1

DT50:

314 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

944 h

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: calculated via Arrhenius calculation

Details on results:

The transformation products could not be ionised and therefore not identified by mass-spectroscopy. The tranformation products identified above are based on the retention times of the HPLC and experience of the sponsor with the environmental behaviour of this kind of dyes.

Results

 

Check of the pH-Value

 

pH-Value of the Test System

measured before application

 

Intended  pH-value	Measured pH‑value
	Preliminary	Definitive Test
	at 50 °C	at 20 °C	at 30 °C	at 50 °C
4.0 ± 0.1	4.033	4.056	4.061	4.062
7.0 ± 0.1	6.950	6.945	6.944	6.951
9.0 ± 0.1	9.031	9.047	9.042	9.041

 

Temperature Monitoring

 

Temperature of the Test System

measured every hour for pH 4, 7 and 9

 

Test	Intended Temperature	Measured Temperature
		Mean ± SD	Min. / Max.
Preliminary	50.0 ± 0.5	50.1 ± 0.01	50.0 / 50.1
pH 4	20.0 ± 0.5	20.1 ± 0.04	20.0 / 20.2
	30.0 ± 0.5	30.0 ± 0.07	29.9 / 30.2
	50.0 ± 0.5	50.0 ± 0.02	49.9 / 50.1
pH 7	20.0 ± 0.5	20.1 ± 0.03	20.0 / 20.2
	30.0 ± 0.5	30.0 ± 0.02	29.9 / 30.0
	50.0 ± 0.5	50.0 ± 0.03	49.9 / 50.1
pH 9	20.0 ± 0.5	20.1 ± 0.03	20.0 / 20.2
	30.0 ± 0.5	30.0 ± 0.02	29.9 / 30.1
	50.0 ± 0.5	50.0 ± 0.03	49.9 / 50.1

 SD = Standard deviation

 

The additional manually taken values confirm the results of the automated temperature recording of the datalogger.

 

 

Preliminary Test

 

In the preliminary test more than 10 % of the test item was degraded after 120 hours at pH 4, 7 and pH 9.

 

Degradation [%] of Reactive Blue 160 at 50 °C after 120 Hours

 

Hydrolysis Time [hours]	Degradation [%]
	pH 4	pH 7	pH 9
120	50.8	25.7	21.5

 

 

 

 

Hydrolysis Results Definitive Test

 

Hydrolysis Results for the Test Item at pH 4 and 20 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.95	2.07
24.3	7.60	2.03
94.6	7.69	2.04
143	8.04	2.08
191	7.61	2.03
264	7.45	2.01
312	7.63	2.03
361	7.78	2.05
434	7.36	2.00
504	7.52	2.02
767	4.02	1.39

 

 

Hydrolysis Results for the Test Item at pH 4 and 30 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.95	2.07
24.7	7.52	2.02
94.9	7.72	2.04
143	7.88	2.06
191	7.72	2.04
265	7.20	1.97
313	7.44	2.01
362	7.41	2.00
434	7.04	1.95
505	7.14	1.97
767	3.57	1.27

 

 

Hydrolysis Results for the Test Item at pH 4 and 50 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.95	2.07
25.3	7.36	2.00
95.9	6.61	1.89
144	6.31	1.84
192	5.57	1.72
265	4.93	1.60
313	4.64	1.53
362	4.11	1.41
435	3.65	1.29
505	3.40	1.22
768	1.23	0.206

 

 

Hydrolysis Results for the Test Item at pH 7 and 20 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.59	2.03
25.2	7.66	2.04
95.8	7.71	2.04
143	8.08	2.09
192	7.77	2.05
265	7.39	2.00
313	7.74	2.05

                Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

 

Hydrolysis Results for the Test Item at pH 7 and 30 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.59	2.03
25.6	7.48	2.01
96.0	7.56	2.02
144	7.92	2.07
192	7.84	2.06
266	7.38	2.00
314	7.66	2.04

                   Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

 

Hydrolysis Results for the Test Item at pH 7 and 50 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.59	2.03
26.1	7.48	2.01
96.7	7.48	2.01
144	7.65	2.04
193	7.02	1.95
266	6.70	1.90

                    Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

 

Hydrolysis Results for the Test Item at pH 9 and 20 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.65	2.03
26.1	7.47	2.01
96.8	7.80	2.05
145	8.13	2.09
193	7.70	2.04
266	7.63	2.03
314	7.67	2.04

                   Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

 

Hydrolysis Results for the Test Item at pH 9 and 30 °C

 

Hydrolysis Time [h]	Concentration [g/L]	Ln Concentration
0.00	7.65	2.03
26.6	7.47	2.01
97.2	7.76	2.05
145	8.16	2.10
193	7.82	2.06
267	7.54	2.02
314	7.90	2.07

                   Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

 

Hydrolysis Results for the Test Item at pH 9 and 50 °C

 

Hydrolysis Time [min]	Concentration [g/L]	Ln Concentration
0.00	7.65	2.03
26.9	7.80	2.05
97.6	7.86	2.06
146	8.09	2.09
194	7.68	2.04
267	7.49	2.01
315	7.49	2.01

                   Stopped, due to stability after 120 h at 50 °C (criteria for performing the definitive test)

 

Kinetics Considerations

 

At pH 7 and 9 the advanced test was stopped, due to stability at 50 °C after 120 h. Therefore no kinetics considerations were done at these pH values.

For pH 4 at all test conditions the ln concentration vs. time plots have regression graphs with slopes significantly non zero. First order reaction kinetics was applied for data computation. A confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved for pH 4 and 50 °C. For pH 4 and 20 and 30 °C, no confirmation of pseudo first order reaction kinetics with coefficients of determination > 0.8 was achieved. Based on the obtained data the pseudo first order reaction kinetics was deemed to be the best fit model for computation of kinetics data.

 

Reaction Rate Constants and Half-Lives at pH 4

 

	pH 4
	20 °C	30 °C	50 °C
Slope of regression graph	-6.41 · 10^-4	-7.86 · 10^-4	-2.21 · 10^-3
Correlation factor [r^2]	0.559	0.627	0.951
Reaction rate constant kobs [1/s]	1.79 · 10^-7	2.19 · 10^-7	6.13 · 10^-7
Half-life T½ [h]	1077	880	314
Confidence interval of half-life T½ [h]	738 to 2712	638 to 1735	276 to 353
Half-life T½ [d]	44.9	36.7	13.1
Confidence interval of half-life T½ [d]	30.8 to 113	26.6 to 72.3	11.5 to 14.7

Rounding differences may be possible, due to the usage of different software

 

 

Arrhenius Calculations

 

Results of Arrhenius Calculations

 

pH value	[°C]	-EA/R	ln A	EA [J * mol^-1]
4	20	-4033	-1.88	3.35 x 10^4
	30
	50

 

 

Transformation Product

 

During LC-DAD analysis one (major) transformation product was observed on peak area basis at all temperatures. This transformation product (hereinafter labelled as T3) could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI⁺ ionisation.

 

At 50 °C three additional (minor) transformation products (hereinafter referred as T1, T2, T4) were observed during LC-DAD analysis. At 20 and 30 °C only the transformation product T2 was observed in addition to T3. These minor transformation products also could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI⁺ ionisation.

 

Based on the small retention time differences and the comparable UV-VIS spectra, it can be assumed, that all observed transformation products are structurally similar to the parent compound. On basis of the available information (non-ionizability, comparable UV-VIS spectra and small retention time differences) and the chemical sense, three transformation product structures were postulated. The postulated structures are probable candidates for the observed signals, but, due to their non-ionizability and the unavailability of reference materials, these structures could not be confirmed. 

It could be assumed that all transformation products are present as copper complexes.

 

Formation of the Transformation Products T2 and T3 at pH 4 and 20 °C

 

Hydrolysis Time [h]	[peak Area, mAU]
	T2	T3
0.00	-	-
24.3	180	-
94.6	439	-
143	416	-
191	370	-
264	282	-
312	291	-
361	336	-
434	277	-
504	-	386
767	73	515

 

 

Formation of the Transformation Products T2 and T3 at pH 4 and 30 °C

 

Hydrolysis Time [h]	[peak Area, mAU]
	T2	T3
0.00	-	-
24.7	225	-
94.9	234	-
143	498	-
191	147	-
265	94	-
313	87	592
362	246	776
434	85	825
505	56	1168
767	-	1716

 

 

Formation of the Transformation Products T1 to T4 at pH 4 and 50 °C

 

Hydrolysis Time [h]	[peak Area, mAU]
	T1	T2	T3	T4
0.00	-	-	-	-
25.3	-	-	668	-
95.9	-	523	2058	-
144	--	462	2713	-
192	-	986	3330	-
265	-	1110	3777	-
313	-	1273	4134	-
362	-	1292	4177	-
435	-	1788	4366	-
505	-	2375	4530	-
768	2072	963	4195	2111

 

 

 

Validity Criteria

 

Validity Criteria

 

Validity criterion	Required	This study
First order kinetic	To confirm first order behavior, the regression graph must have a correlation factor of ≥ 0.8.	pH 4 20 °C: 0.563 30 °C: 0.632 50 °C: 0.949
Temperature	The test temperature should be within ± 0.5 °C of the nominal temperature.	pH 4 20.1 ± 0.04 30.0 ± 0.07 50.0 ± 0.02
Test systems	The pH values of the buffer solutions should be in the range of ± 0.1 pH at test temperature.	Fulfilled
Sensitivity	Sensitivity of the analytical method should be sufficient to quantify test item concentrations at least down to a 90% reduction of the initial concentration.	Fulfilled

 

 

Validity criteria fulfilled:

yes

Conclusions:

The test item showed a slow hydrolysis rate for pH 4 at 20 and 30 °C with a calculated half-life of 39.3 days at 25°C and a moderate hydrolysis rate for pH 4 at 50 °C.
At pH 7 and 9 no significant reduction of the test item concentration was observed at 50°C and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.
One major (T3) and three additional (minor) transformation products (T1, T2, T4) were observed. These transformation products could not be ionised and hence not mass-spectroscopically identified. It is therefore concluded that they consist of copper complex structures similar to the test item itself.

Executive summary:

Hydrolysis as a function of pH was determined according to OECD Guideline No. 111 and Council Regulation (EC) No. 440/2008, Method C.7 for the test item Reactive Blue 160 (batch number: 15741) from 2019 08 01 to 2020-04-28 at the test facility.

Analyses of the test item Reactive Blue 160 were performed via LC DAD on a reversed phase analytical column using the test item as external standard. The analytical method was validated with satisfactory results with regard to linearity, accuracy, precision and specificity.

The preliminary test was conducted with a test item concentration of 1.5 g/L in buffer solutions at pH 4, 7 and 9 at 50 °C. For all pH values the definitive test was performed, as a significant reduction (> 10%) of the test item concentration was observed in the preliminary test.

The definitive test was conducted with a test item concentration of 7.5 g/L in buffer solutions at pH 4, 7 and 9 at temperatures of 20, 30 and 50 °C. Samples were taken at test start (0 h) and at 6   10 spaced time points until test end. Pure test system (buffer solution at the respective pH value) was analyzed at test start and test end and there was no analytical interference with the test item.

At pH 7 and 9 no significant reduction of the test item concentration was observed after 266 h at pH 7 and 315 h at pH 9 at 50 °C. Therefore, the definitive study at pH 7 and 9 was stopped and the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.

Reaction rate constants, half-lives and activation energies were calculated from the analyzed samples at pH 4 based on a first order reaction kinetics model.

The test item showed a slow hydrolysis rate (> 30 d) for pH 4 at 20 and 30 °C and a moderate hydrolysis (2.4 h ≤ t1/2 ≤ 30 d) for pH 4 at 50 °C.

Classification Scheme based on Hydrolysis Half-life

Classification       t ½

fast       ≤ 2.4 h

moderate       ≥ 2.4 h and ≤ 30 d

slow       > 30 d

 

Reaction Rate Constants and Half-Lives at pH 4

      pH 4

      20 °C       30 °C       50 °C       25 °C 1)

Reaction rate constant kobs [1/s]       1.79 · 10-7       2.19 · 10-7       6.13 · 10-7       2.04· 10-7

Half-life T½ [h]       1077       880       314       944

Half-life T½ [d]       44.9       36.7       13.1       39.3

Number of data points       11       11       11       EA = 3.35 · 104 J * mol-1

Slope of regression graph       significantly non-zero       

1)       =  values calculated via Arrhenius equation

EA       = activation energy

During LC-DAD analysis one (major) transformation product was observed. This transformation product (hereinafter labelled as T3) could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI+ ionisation.

At 50 °C three additional (minor) transformation products (hereinafter referred as T1, T2, T4) were observed during LC-DAD analysis. At 20 and 30 °C only the transformation product T2 was additionally observed. These minor transformation products also could not be mass-spectroscopically identified, as no chromatographic signals could be generated for the observed transformation products using LC-MS employing ESI+ ionisation.

On basis of the available information (non-ionizability, comparable UV-VIS spectra and small retention time differences) and the chemical sense, three transformation product structures were postulated. The postulated structures are probable candidates for the observed chromatographic transformation product signals.

Description of key information

The test item showed a slow hydrolysis rate for pH 4 at 20 and 30 °C with a calculated half-life of 39.3 days at 25°C and a moderate hydrolysis rate for pH 4 at 50 °C.

At pH 7 and 9 no significant reduction of the test item concentration was observed at 50°C and therefore the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.

Key value for chemical safety assessment

Half-life for hydrolysis:

39.3 d

at the temperature of:

25 °C

Additional information

Hydrolysis as a function of pH was determined according to OECD Guideline No. 111 and Council Regulation (EC) No. 440/2008, Method C.7. Analyses of the test item Reactive Blue 160 were performed via LC‑DAD on a reversed phase analytical column using the test item as external standard. The analytical method was validated with satisfactory results with regard to linearity, accuracy, precision and specificity.

The preliminary test was conducted with a test item concentration of 1.5 g/L in buffer solutions at pH 4, 7 and 9 at 50 °C. For all pH‑values the definitive test was performed, as a significant reduction (> 10%) of the test item concentration was observed in the preliminary test. The definitive test was conducted with a test item concentration of 7.5 g/L in buffer solutions at pH 4, 7 and 9 at temperatures of 20, 30 and 50 °C. Samples were taken at test start (0 h) and at 6 ‑ 10 spaced time points until test end. Pure test system (buffer solution at the respective pH‑value) was analyzed at test start and test end and there was no analytical interference with the test item. At pH 7 and 9 no significant reduction of the test item concentration was observed after 266 h at pH 7 and 315 h at pH 9 at 50 °C. Therefore, the definitive study at pH 7 and 9 was stopped and the test item was considered as hydrolytically stable under this condition.

Reaction rate constants, half-lives and activation energies were calculated from the analyzed samples at pH 4 based on a first order reaction kinetics model.

Reaction Rate Constants and Half-Lives at pH 4

	pH 4
	20 °C	30 °C	50 °C	25 °C ^1)
Reaction rate constant kobs [1/s]	1.79 · 10^-7	2.19 · 10^-7	6.13 · 10^-7	2.04· 10^-7
Half-life T½ [h]	1077	880	314	944
Half-life T½ [d]	44.9	36.7	13.1	39.3
Number of data points	11	11	11	EA = 3.35 · 10^4J * mol^-1
Slope of regression graph	significantly non-zero

1)     =  values calculated via Arrhenius equation

E_A     = activation energy

The test item showed a slow hydrolysis rate (> 30 d) for pH 4 at 20 and 30 °C and a moderate hydrolysis (2.4 h ≤ t_1/2 ≤ 30 d) for pH 4 at 50 °C.

At pH 7 and 9, the test item was considered as hydrolytically stable under this condition and a half-life of > 1 year could be assumed for environmental typical temperatures.