Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 231-781-8 | CAS number: 7727-21-1
Hydrolysis
Administrative data
Link to relevant study record(s)
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- 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:
- 2004-11-23
- Deviations:
- no
- GLP compliance:
- no
- Remarks:
- In-house quality and environmental management system in place. Certified in accordance with ISO 9001:2015 and ISO 14001:2015.
- Radiolabelling:
- no
- Analytical monitoring:
- yes
- Remarks:
- Ion chromatography
- Buffers:
- 1) pH-4 buffer solution:
20.43 g potassium hydrogen phthalate were dissolved in 1 L distilled water at 20 °C. To 500 mL of that solution 4.0 mL NaOH 0.1 M and water are added to an overall volume of 1.0 L.
2) pH-7 buffer solution:
13.61 g potassium hydrogen phosphate were dissolved in 1 L distilled water at 20 °C. To 500 mL of that solution 296.3 mL NaOH 0.1 M and water are added to an overall volume of 1.0 L.
3) pH-9 buffer solution:
6.19 g boric acid were dissolved in 1 L distilled water at 20 °C. To 500 mL of that solution 213.0 mL NaOH 0.1 M and water are added to an overall volume of 1.0 L. - Details on test conditions:
- TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: standard laboratory glassware
- Sterilisation method: none
- Lighting: darkness
- Measures taken to avoid photolytic effects:yes, the test was performed unter total darkness.
- Measures to exclude oxygen: none.
TEST MEDIUM
- Volume used/treatment: 50 mL
- Kind and purity of water: distilled water
OTHER TEST CONDITIONS
- Adjustment of pH: none - Duration:
- 4 d
- pH:
- 9
- Temp.:
- 60 °C
- Duration:
- 4 d
- pH:
- 7
- Temp.:
- 60 °C
- Duration:
- 4 d
- pH:
- 4
- Temp.:
- 60 °C
- Duration:
- 32 d
- pH:
- 9
- Temp.:
- 25 °C
- Duration:
- 32 d
- pH:
- 7
- Temp.:
- 25 °C
- Duration:
- 32 d
- pH:
- 4
- Temp.:
- 25 °C
- Duration:
- 31 d
- pH:
- 9
- Temp.:
- 10 °C
- Duration:
- 31 d
- pH:
- 7
- Temp.:
- 10 °C
- Duration:
- 31 d
- pH:
- 4
- Temp.:
- 10 °C
- Number of replicates:
- 2
- Positive controls:
- no
- Negative controls:
- no
- Preliminary study:
- The preliminary hydrolysis test was performed at 50 °C at pH values of 4, 7 and 9. The samples were incubated for five days and analyzed afterwards.
S2O8[2-] (t = 0) S2O8[2-] (t = 5 days)
pH 4 88.21 7.77
pH 7 84.93 13.37
pH 9 97.45 12.33
The persulfate was hydrolyzed to similar degrees at all tested pH values. Given the fact, that in each case the amount of hydrolyzed substance is more than 10 %, the substance cannot be considered hydrolytically stable. Thus, an in-detail study was conducted. - Transformation products:
- not specified
- Key result
- pH:
- 7
- Temp.:
- 12 °C
- Hydrolysis rate constant:
- 0 h-1
- DT50:
- 1 698.18 h
- Type:
- (pseudo-)first order (= half-life)
- Key result
- pH:
- 4
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.025 h-1
- DT50:
- 27.7 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 7
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.019 h-1
- DT50:
- 36.5 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 9
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.019 h-1
- DT50:
- 36.5 h
- Type:
- (pseudo-)first order (= half-life)
- Validity criteria fulfilled:
- yes
- Conclusions:
- APS was shown to be hydrolitically stable at 10 °C and pH 4, 7 and 9, a minor hydrolysis was observed at 25 °C, whereas, a very strong hydrolysis at 60 °C was observed within 4 days. The DT50 at pH 4 and 60 °C was determined to be 27.2 h, at pH 7 and 9 and 60 °C the DT50 was determined to be 36.5 h. The DT50 at environmentally relevant temperature (12 °C) and pH 7 was extrapolated to be 1698.18 h (70.76 d).
- Executive summary:
A study according to OECD TG 111 was performed to determine the hydrolysis potential of the test item. Inittialla, a Tier 1 tests at for 5 days at 50 °C and H 4, 7 and 9 was performed. Hydrolisys of more than 10 % was observed at all pH levels. Thus, a Tier 2 hydrolysis test was conducted at 10, 25 and 60 °C and pH 4, 7 and 9. Hydrolysis studies at 10 and 25 °C run for ca. 30 days, while at 60 °C the hydrolysis process was finished after 4 days. APS was shown to be hydrolitically stable at 10 °C and pH 4, 7 and 9, a minor hydrolysis was observed at 25 °C, whereas, a very strong hydrolysis at 60 °C was observed within 4 days. The DT50 at pH 4 and 60 °C was determined to be 27.2 h. The DT50 at environmentally relevant temperature (12 °C) was extrapolated to be 1288.76 h (53.7 d).
- Endpoint:
- hydrolysis
- Type of information:
- read-across based on grouping of substances (category approach)
- Adequacy of study:
- weight of evidence
- Justification for type of information:
- READ ACROSS CATEGORY APPROACH
A category group was formed with dipotassium peroxodisulphate (KPS), disodium peroxodisulphate (SPS) and diammonium peroxodisulphate (APS). Several physico-chemical, fate, ecotoxicological and toxicological endpoints were assessed using the category approach. Please refer to the read across justification in chapter 13 for further information. - Transformation products:
- not specified
- Key result
- pH:
- 7
- Temp.:
- 12 °C
- Hydrolysis rate constant:
- 0 h-1
- DT50:
- 1 698.18 h
- Type:
- (pseudo-)first order (= half-life)
- Key result
- pH:
- 4
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.025 h-1
- DT50:
- 27.7 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 7
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.019 h-1
- DT50:
- 36.5 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 9
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.019 h-1
- DT50:
- 36.5 h
- Type:
- (pseudo-)first order (= half-life)
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Study period:
- from 2020-07-03 to 2020-08-26
- 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:
- 2004-11-23
- Deviations:
- no
- GLP compliance:
- no
- Remarks:
- In-house quality and environmental management system in place. Certified in accordance with ISO 9001:2015 and ISO 14001:2015.
- Radiolabelling:
- no
- Analytical monitoring:
- yes
- Remarks:
- Ion chromatography
- Buffers:
- 1) pH-4 buffer solution:
20.43 g potassium hydrogen phthalate were dissolved in 1 L distilled water at 20 °C. To 500 mL of that solution 4.0 mL NaOH 0.1 M and water are added to an overall volume of 1.0 L.
2) pH-7 buffer solution:
13.61 g potassium hydrogen phosphate were dissolved in 1 L distilled water at 20 °C. To 500 mL of that solution 296.3 mL NaOH 0.1 M and water are added to an overall volume of 1.0 L. - Details on test conditions:
- TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: standard laboratory glassware
- Sterilisation method: none
- Lighting: darkness
- Measures taken to avoid photolytic effects:yes, the test was performed unter total darkness.
- Measures to exclude oxygen: none.
TEST MEDIUM
- Volume used/treatment: 50 mL
- Kind and purity of water: distilled water
OTHER TEST CONDITIONS
- Adjustment of pH: none - Duration:
- 31 h
- pH:
- 7
- Temp.:
- 60 °C
- Duration:
- 55 h
- pH:
- 4
- Temp.:
- 60 °C
- Duration:
- 32 d
- pH:
- 4
- Temp.:
- 25 °C
- Number of replicates:
- 2
- Positive controls:
- no
- Negative controls:
- no
- Preliminary study:
- A preliminary hydrolysis test was performed at 50 °C at pH values of 4, 7 and 9 with the category member APS. The samples were incubated for five days and analyzed afterwards.
S2O8[2-] (t = 0) S2O8[2-] (t = 5 days)
pH 4 88.21 7.77
pH 7 84.93 13.37
pH 9 97.45 12.33
The persulfate was hydrolyzed to similar degrees at all tested pH values. Given the fact, that in each case the amount of hydrolyzed substance is more than 10 %, the substance cannot be considered hydrolytically stable. Thus, an in-detail study was conducted. - Test performance:
- The category member APS was determined to be hydrolitically stable at 10 °C and pH 4, 7 and 9. Similar stability was observed in the tests at 25 °C. To adequatelly represent the hydrolysis behaviour of KPS, only pH 4 was tested at 25 °C. If any hydrolyses was observed at pH 4 and 25 °C, further measurements at higher pH-values (7 and/or 9) would have been performed at this temperature.
- Transformation products:
- not specified
- Key result
- pH:
- 7
- Temp.:
- 12 °C
- Hydrolysis rate constant:
- 0.001 h-1
- DT50:
- 558.3 h
- Type:
- (pseudo-)first order (= half-life)
- Key result
- pH:
- 4
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.098 h-1
- DT50:
- 7.1 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 7
- Temp.:
- 60 °C
- Hydrolysis rate constant:
- 0.058 h-1
- DT50:
- 12 h
- Type:
- (pseudo-)first order (= half-life)
- Validity criteria fulfilled:
- yes
- Conclusions:
- KPS showed minor hydrolysis at 25 °C, which was not continuously, but only towards the end of the monitored timeframe. Whereas at 60 °C strong hydrolysis (faster at acidic than at neutral pH values) was observed. The DT50 at pH 4 and 60 °C was determined to be 7.1 h and at pH 7 and 60 °C the DT50 was determined to be 12 h. The DT50 at environmentally relevant temperature (12 °C) and pH 7 was extrapolated to be 558.3 h (23.3 d).
- Executive summary:
A study according to OECD TG 111 was performed to determine the hydrolysis potential of the test item. Initially, a Tier 1 tests at for 5 days at 50 °C and pH 4, 7 and 9 were performed with the category member APS. Hydrolisys of more than 10 % was observed at all pH levels. Thus, a Tier 2 hydrolysis test was conducted at 10, 25 and 60 °C and pH 4, 7 and 9 with APS. It was shown that the persulfate is hydrolytically stable at 10 °C and different pH-levels, therefore, hydrolysis studies with KPS were performed only at the relevant test conditions. Hydrolysis studies at 25 °C and pH 4 and 60 °C and pH 4 and 7 were conducted with KPS. The test at 25 °C run for ca. 30 days, while at 60 °C the hydrolysis process was finished after 2 - 4 days. KPS showed minor hydrolysis at 25 °C, which was not continuously, but only towards the end of the monitored timeframe. Whereas at 60 °C strong hydrolysis (faster at acidic than at neutral pH values) was observed. The DT50 at pH 4 and 60 °C was determined to be 7.1 h and at pH 7 and 60 °C the DT50 was determined to be 12 h. The DT50 at environmentally relevant temperature (12 °C) and pH 7 was extrapolated to be 558.3 h (23.3 d).
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- disregarded due to major methodological deficiencies
- Study period:
- 1951
- Reliability:
- 3 (not reliable)
- Rationale for reliability incl. deficiencies:
- significant methodological deficiencies
- Remarks:
- publicly available literature
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- OECD Guideline 111 (Hydrolysis as a Function of pH)
- Deviations:
- yes
- Remarks:
- The decomposition rates of potassium persulfate in water were investigated at various pH values, ranging from 1 to 10. Assessments were limited to a temperature of 50 °C.
- GLP compliance:
- no
- Radiolabelling:
- no
- Analytical monitoring:
- not specified
- Details on sampling:
- No information available
- Buffers:
- Carbonate buffer; phosphate buffer
- Details on test conditions:
- In the kinetics experiments 100 mL-portions of persulfate and buffer solution were placed in separate vessels and brought to the desired temperature in a thermostat and then mixed. Samples were withdrawn periodically by pipette and were added to a tenfold excess of water at room temperature to practically stop the reaction. Gelatin and supporting electrolyte were then added and the solution was diluted for a known volume. Samples were then analysed using polarographic analysis.
- Number of replicates:
- NA
- Positive controls:
- not specified
- Negative controls:
- not specified
- Statistical methods:
- NA
- Transformation products:
- not specified
- pH:
- 1
- Temp.:
- 50 °C
- Hydrolysis rate constant:
- 0.035 h-1
- DT50:
- 20 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 1.6
- Temp.:
- 50 °C
- Hydrolysis rate constant:
- 0.011 h-1
- DT50:
- 65 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 3
- Temp.:
- 50 °C
- Hydrolysis rate constant:
- 0.006 h-1
- DT50:
- 120 h
- Type:
- (pseudo-)first order (= half-life)
- Key result
- pH:
- 7
- Temp.:
- 50 °C
- Hydrolysis rate constant:
- 0.005 h-1
- DT50:
- 130 h
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 10
- Temp.:
- 50 °C
- Hydrolysis rate constant:
- 3.3 h-1
- DT50:
- 210 h
- Type:
- (pseudo-)first order (= half-life)
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- Potassium persulfate hydrolyses in water, forming potassium ions and persulfate anions. The persulfate anions further oxidize water producing oxygen, sulphate ions and hydrogen ions.
- Executive summary:
Hydrolysis: In alkaline, neutral and dilute acid solutions persulfate decomposes according to reaction (1), while in strongly acid solutions reactions (2) and (3) occur:
S2O82-+ H2O --> 2 HSO4- + ½ O2 (1)
H2S2O8+ H2O --> H2SO5 + H2SO4 (2)
H2SO5 + H2O --> H2O2 + H2SO4 (3)
All degradation products are ubiquitous to the natural environment. The rates of decomposition increased with decreasing pH ranging from 0.035 h-1 at pH 1 to 3.3 h-1 at pH 10, respectively DT50 of 20 hour to DT50 of 21 hour. The rate of hydrolysis at pH 7 and 12 °C was calculated using the Arrhenius equation resulting in 3.6E-04 h-1 and DT50 = 1929.6 h (80.4 days).
Referenceopen allclose all
As the APS was found to be unstable at all tested pH values, advanced tests were conducted for all three conditions. The buffered APS solutions were thermostated at 10, 25, as well as 60 °C, respectively.
Hydrolysis at 10 °C
Table 1: Analytic results of the hydrolysis of APS at 10 °C and pH = 4.
APS (10 °C, pH = 4) |
||||||
Day |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
|
|
|
Sample 1 |
Sample 2 |
|
|
1 |
0 (Start) |
0.1171 |
85.40 |
85.35 |
4.03 |
|
4 |
1 |
0.1151 |
85.91 |
85.71 |
4.05 |
|
8 |
2 |
0.1142 |
85.99 |
85.43 |
4.10 |
|
11 |
3 |
0.1157 |
87.98 |
88.00 |
4.08 |
|
15 |
4 |
0.1142 |
88.54 |
88.39 |
4.10 |
|
18 |
5 |
0.1162 |
88.65 |
87.68 |
3.97 |
|
22 |
6 |
0.1147 |
90.90 |
92.08 |
3.90 |
|
25 |
7 |
0.1149 |
91.79 |
92.33 |
4.08 |
|
29 |
8 |
0.1143 |
92.38 |
92.47 |
4.10 |
|
31 |
9 |
0.1182 |
94.54 |
94.78 |
4.06 |
0.5 |
APS is hydrolytically stable at 10 °C and pH=4. Interestingly, the measured APS content was found to increase over the measurement period. The sulfate content of the final sample 9 was determined to be 0.5 %, further confirming the stability of APS under these conditions.
Table 2: Analytic results of the hydrolysis of APS at 10 °C and pH = 7.
APS (10 °C, pH = 7) |
||||||
Day |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
|
|
|
Sample 1 |
Sample 2 |
|
|
1 |
0 (Start) |
0.1201 |
85.53 |
85.06 |
6.97 |
|
4 |
1 |
0.1148 |
86.40 |
84.98 |
6.97 |
|
8 |
2 |
0.1143 |
85.85 |
86.16 |
7.03 |
|
11 |
3 |
0.1142 |
88.27 |
88.29 |
7.04 |
|
15 |
4 |
0.1177 |
88.94 |
88.00 |
7.05 |
|
18 |
5 |
0.1155 |
89.37 |
87.87 |
6.96 |
|
22 |
6 |
0.1165 |
91.54 |
91.77 |
6.88 |
|
25 |
7 |
0.1159 |
82.02 |
91.78 |
7.00 |
|
29 |
8 |
0.1160 |
92.56 |
93.17 |
7.00 |
|
31 |
9 |
0.1185 |
94.89 |
93.52 |
6.96 |
0.1 |
The results from the study at pH = 4 can be confirmed for pH = 7. APS is hydrolytically stable under these conditions (10 °C and pH=7) as well. Likewise, the measured APS content was found to increase over the measurement period. The sulfate content of the final sample 9 was determined to 0.1 %, confirming the stability of APS under these conditions.
Table 3: Analytic results of the hydrolysis of APS at 10 °C and pH = 9.
APS (10 °C, pH = 9) |
||||||
Day |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
|
|
|
Sample 1 |
Sample 2 |
|
|
1 |
0 (Start) |
0.1155 |
84.05 |
84.16 |
8.86 |
|
4 |
1 |
0.1148 |
84.80 |
85.16 |
8.75 |
|
8 |
2 |
0.1152 |
85.95 |
85.25 |
8.80 |
|
11 |
3 |
0.1149 |
88.24 |
88.60 |
8.86 |
|
15 |
4 |
0.1161 |
88.60 |
88.14 |
8.86 |
|
18 |
5 |
0.1176 |
89.19 |
87.77 |
8.85 |
|
22 |
6 |
0.1166 |
90.30 |
91.72 |
8.70 |
|
25 |
7 |
0.1151 |
91.07 |
92.13 |
8.80 |
|
29 |
8 |
0.1145 |
92.56 |
92.68 |
8.70 |
|
31 |
9 |
0.1183 |
93.78 |
93.52 |
8.75 |
0.6 |
The results from the study at pH = 4 and 7 can be confirmed for pH = 9 as well. APS is hydrolytically stable under these conditions (10 °C and pH=9) as well. Likewise, the measured APS content was found to increase over the measurement period. The sulfate content of the final sample 9 was determined to 0.6 %, confirming the stability of APS under these conditions.
Hydrolysis at 25 °C
Table 4: Analytic results of the hydrolysis of APS at 25 °C and pH = 4.
APS (25 °C, pH = 4) |
||||||
Day |
Sample-ID |
weighed-in sample [g] |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
1 |
0 (Start) |
0.1117 |
85.66 |
85.95 |
4.08 |
|
5 |
1 |
0.1133 |
85.62 |
85.57 |
4.09 |
|
8 |
2 |
0.1128 |
85.57 |
85.40 |
4.05 |
|
12 |
3 |
0.1180 |
85.95 |
86.14 |
3.94 |
|
15 |
4 |
0.1121 |
85.21 |
85.41 |
4.03 |
|
19 |
5 |
0.1138 |
85.20 |
85.40 |
4.01 |
|
22 |
6 |
0.1125 |
84.72 |
84.21 |
4.05 |
|
26 |
7 |
0.1123 |
84.45 |
84.39 |
3.99 |
|
29 |
8 |
0.1142 |
77.80 |
78.07 |
3.81 |
|
32 |
9 |
0.1121 |
68.94 |
68.82 |
3.82 |
3.22 |
APS is hydrolytically stable until after sample 7 (after approx. 3 weeks). Afterwards, the APS content was found to decrease significantly. Likewise, the pH value drops to 3.8 indicating that the buffer is used up at this point. The sulfate content was analysed to 3.2% which is a lower value than anticipated from the decreased amount of persulfate. This might be explained by the fact that persulfates can decompose via a different pathway in the acidic milieu and form monoperoxosulfate SO52- as an intermediate decomposition product which was not determined analytically during this study.
Table 5: Analytic results of the hydrolysis of APS at 25 °C and pH = 7.
APS (25 °C, pH = 7) |
||||||
Day |
Sample-ID |
weighed-in sample [g] |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
1 |
0 (Start) |
0.1122 |
84.63 |
84.97 |
7.03 |
|
5 |
1 |
0.1135 |
85.64 |
85.77 |
6.99 |
|
8 |
2 |
0.1158 |
86.19 |
86.12 |
6.96 |
|
12 |
3 |
0.1157 |
86.50 |
86.69 |
6.93 |
|
15 |
4 |
0.1183 |
86.78 |
86.84 |
6.97 |
|
19 |
5 |
0.1134 |
86.67 |
86.57 |
6.94 |
|
22 |
6 |
0.1122 |
87.95 |
87.67 |
7.00 |
|
26 |
7 |
0.1113 |
87.95 |
88.00 |
6.93 |
|
29 |
8 |
0.1170 |
82.39 |
82.82 |
6.85 |
|
32 |
9 |
0.1136 |
82.98 |
83.43 |
6.81 |
2.40 |
The results from the study at pH = 7 indicate that almost no hydrolysis was observed under these conditions. After one month the persulfate content was reduced by approx. 2.5 %. The analysed amount of SO42- in the terminal sample was 2.40 % which is in good accordance to the decomposed amount of persulfate. Analogous to the study at pH = 4 the final pH-value of the sample is slightly lower than the original sample at the beginning of the measurement indicating that the buffer was at its limit.
Table 6: Analytic results of the hydrolysis of APS at 25 °C and pH = 9.
APS (25 °C, pH = 9) |
||||||
Day |
Sample-ID |
weighed-in sample [g] |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
1 |
0 (Start) |
0.1130 |
85.66 |
85.95 |
8.76 |
|
5 |
1 |
0.1121 |
85.77 |
85.99 |
8.72 |
|
8 |
2 |
0.1144 |
86.51 |
86.43 |
8.71 |
|
12 |
3 |
0.1130 |
86.49 |
86.52 |
8.69 |
|
15 |
4 |
0.1144 |
86.75 |
87.00 |
8.71 |
|
19 |
5 |
0.1146 |
87.46 |
87.09 |
8.67 |
|
22 |
6 |
0.1122 |
87.07 |
86.94 |
8.70 |
|
26 |
7 |
0.1121 |
87.46 |
87.21 |
8.68 |
|
29 |
8 |
0.1135 |
82.07 |
82.77 |
8.51 |
|
32 |
9 |
0.1124 |
83.00 |
82.58 |
8.52 |
2.94 |
The results from the study at pH = 9 is very similar to the result obtained at pH = 7. APS is hydrolytically stable under these conditions as well. After one month the persulfate content was reduced by approx. 3 %. The analysed amount of SO42- in the terminal sample was 2.94 % which is in good accordance to the decomposed amount of persulfate. Analogous to the study at pH = 4 the final pH-value of the sample is slightly lower than the original sample at the beginning of the measurement indicating that the buffer was at its limit.
Hydrolysis at 60 °C
Table 7: Analytic results of the hydrolysis of APS at 60 °C and pH = 4.
APS (60 °C, pH = 4) |
||||||
Date, Time |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
2019-03-25, 07:00 |
0 (Start) |
0.1138 |
84.48 |
84.37 |
4.09 |
|
2019-03-25, 15:00 |
1 |
0.1127 |
59.51 |
59.42 |
3.83 |
|
2019-03-26, 06:00 |
2 |
0.1136 |
37.68 |
38.58 |
3.60 |
|
2019-03-26, 11:00 |
3* |
0.1138 |
28.74 |
28.76 |
3.47 |
|
2019-03-26, 15:00 |
4* |
0.1134 |
28.56 |
28.94 |
3.46 |
|
2019-03-27, 06:00 |
5* |
0.1130 |
20.00 |
19.09 |
3.43 |
|
2019-03-27, 13:00 |
6* |
0.1134 |
15.97 |
15.82 |
3.42 |
|
2019-03-28, 06:00 |
7** |
0.1150 |
11.06 |
11.05 |
3.35 |
|
2019-03-28, 13:00 |
8** |
0.1123 |
10.45 |
10.43 |
3.36 |
|
2019-03-29, 06:00 |
9** |
0.1130 |
7.53 |
7.53 |
3.36 |
81.87*** |
* dilution factor for ion chromatographic analysis = 8000
** dilution factor for ion chromatographic analysis = 4000
*** dilution factor for ion chromatographic analysis = 80000
APS decomposes rather quickly under the test conditions. After approx. 4 days less than 10 % of the original content was found in the respective samples. The amount of sulfate detected in the terminal sample is in good agreement with that finding. At this temperature it was not possible to hold the pH value of the buffered solutions at 4. It drifted steadily to 3.36 throughout the study.
Table 8: Analytic results of the hydrolysis of APS at 60 °C and pH = 7.
APS (60 °C, pH = 7) |
||||||
Date, Time |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
2019-03-25, 07:00 |
0 (Start) |
0.1146 |
85.23 |
85.19 |
7.05 |
|
2019-03-25, 15:00 |
1 |
0.1123 |
74.68 |
74.19 |
6.96 |
|
2019-03-26, 06:00 |
2 |
0.1128 |
53.73 |
54.32 |
6.63 |
|
2019-03-26, 11:00 |
3* |
0.1138 |
49.63 |
48.97 |
6.57 |
|
2019-03-26, 15:00 |
4* |
0.1143 |
46.77 |
46.95 |
6.55 |
|
2019-03-27, 06:00 |
5* |
0.1129 |
32.42 |
32.33 |
6.41 |
|
2019-03-27, 13:00 |
6* |
0.1128 |
30.41 |
30.42 |
6.40 |
|
2019-03-28, 06:00 |
7** |
0.1139 |
22.69 |
22.90 |
6.21 |
|
2019-03-28, 13:00 |
8** |
0.1127 |
20.82 |
21,06 |
6.20 |
|
2019-03-29, 06:00 |
9** |
0.1158 |
14.29 |
14.22 |
6.06 |
72.04*** |
* dilution factor for ion chromatographic analysis = 8000
** dilution factor for ion chromatographic analysis = 4000
*** dilution factor for ion chromatographic analysis = 40000
APS decomposes rather quickly at these conditions, however somewhat slower than at pH = 4. The amount of sulfate detected in the terminal sample (72.04 %) is in good agreement with the corresponding APS content. As for the previous study at pH = 4 it was also not possible to keep the pH value of the buffered solutions at 7. It drifted steadily to a final value of 6.06 during the study.
Table 9: Analytic results of the hydrolysis study of APS at 60 °C and pH = 9.
APS (60 °C, pH = 9) |
||||||
Date, Time |
Sample-ID |
weighed-in |
S2O82- [%] |
pH |
SO42- |
|
Sample 1 |
Sample 2 |
|||||
2019-03-25, 07:00 |
0 (Start) |
0.1160 |
85.86 |
85.77 |
8.88 |
|
2019-03-25, 15:00 |
1 |
0.1165 |
69.94 |
70.58 |
8.71 |
|
2019-03-26, 06:00 |
2 |
0.1122 |
50.78 |
51.25 |
8.34 |
|
2019-03-26, 11:00 |
3* |
0.1116 |
45.03 |
44.50 |
8.19 |
|
2019-03-26, 15:00 |
4* |
0.1136 |
43.53 |
43.38 |
8.16 |
|
2019-03-27, 06:00 |
5* |
0.1130 |
35.42 |
35.33 |
7.68 |
|
2019-03-27, 13:00 |
6* |
0.1143 |
31.89 |
31.59 |
7.60 |
|
2019-03-28, 06:00 |
7** |
0.1117 |
21.52 |
21.65 |
7.00 |
|
2019-03-28, 13:00 |
8** |
0.1165 |
19.21 |
19.26 |
3.30 |
|
2019-03-29, 06:00 |
9** |
0.1159 |
13.60 |
12.93 |
2.93 |
78.17*** |
* dilution factor for ion chromatographic analysis = 8000
** dilution factor for ion chromatographic analysis = 4000
*** dilution factor for ion chromatographic analysis = 40000
APS decomposes at 60 °C and pH=9 with a similar rate compared to the study at pH = 7. The amount of sulfate detected in the terminal sample is again in good agreement with the corresponding APS content. As for the previous studies at 60 °C it was also not possible to keep the pH value of the buffered solutions at 9. Especially close to the end of the study the pH value of the sample fell rapidly to a final value of 2.93.
Hydrolysis tests were conducted at 25 °C, pH = 4, as well as 60 °C, pH = 4 and 60 °C, pH = 7.
Hydrolysis at 25 °C
Table 1: Analytic results of the hydrolysis of KPS at 25 °C and pH = 4.
KPS (25 °C, pH = 4) | ||||||
Day | Sample-ID | weighed-in sample [g] | S2O82- [%] | pH | SO42- | |
Sample 1 | Sample 2 | |||||
1 | 0 (Start) | 0.1355 | 70.50 | 70.62 | 4.02 |
|
4 | 1 | 0.1356 | 70.58 | 70.47 | 4.02 |
|
7 | 2 | 0.1355 | 69.50 | 69.61 | 4.02 |
|
11 | 3 | 0.1344 | 68.74 | 68.52 | 4.03 |
|
14 | 4 | 0.1344 | 68.64 | 68.52 | 4.03 |
|
18 | 5 | 0.1346 | 68.73 | 68.35 | 3.99 |
|
21 | 6 | 0.1378 | 68.59 | 68.67 | 4.05 |
|
25 | 7 | 0.1355 | 67.92 | 68.12 | 4.02 |
|
28 | 8 | 0.1356 | 66.16 | 66.45 | 4.00 |
|
32 | 9 | 0.1352 | 64.65 | 64.91 | 3.98 | 7.02 |
KPS is hydrolytically stable until after sample 7 (after approx. 3 weeks). Afterwards, the KPS content was found to decrease significantly. The pH value was stable over the study. The final sulfate content was analyzed to be 7.02 % matching the reduced persulfate content within the margin of error.
Hydrolysis at 60 °C
Table 2: Analytic results of the hydrolysis of APS at 60 °C and pH = 4.
KPS (60 °C, pH = 4) | ||||||
Date, Time | Sample-ID | weighed-in | S2O82- [%] | pH | SO42- | |
Sample 1 | Sample 2 | |||||
2020-07-20, 07:00 | 0 (Start) | 0.1363 | 71.45 | 71.41 | 4.02 |
|
2020-07-20, 15:00 | 1 | 0.1355 | 32.03 | 31.62 | 3.55 |
|
2020-07-21, 06:00 | 2* | 0.1344 | 7.25 | 7.22 | 3.20 |
|
2020-07-21, 14:00 | 3** | 0.1346 | 3.48 | 3.48 | 3.21 | 70.05*** |
* dilution factor for ion chromatographic analysis = 8000
** dilution factor for ion chromatographic analysis = 4000
*** dilution factor for ion chromatographic analysis = 80000
KPS decomposes rather quickly under the given test conditions. After approx. 24 hours less than 10 % of the original content was found in the respective samples. The amount of sulfate detected in the terminal sample is in good agreement with that finding. At this temperature it was not possible to hold the pH value of the buffered solutions at 4. It drifted steadily to 3.21 throughout the study.
The decomposition of PPS follows a first order kinetic under these conditions. The rate constant (inverse of the trend line’s slope) can be obtained with a coefficient of determination of R2 = 99.9 % to a value of k = 0.098 h-1. The respective half-life value was calculated to be 7.1 h.
Table 3: Analytic results of the hydrolysis of KPS at 60 °C and pH = 7.
KPS (60 °C, pH = 7) | ||||||
Date, Time | Sample-ID | weighed-in | S2O82- [%] | pH | SO42- | |
Sample 1 | Sample 2 | |||||
2020-07-27, 07:00 | 0 (Start) | 0.1346 | 73.05 | 72.27 | 7.02 |
|
2020-07-27, 13:00 | 1 | 0.1348 | 63.33 | 63.03 | 6.98 |
|
2020-07-28, 06:00 | 2 | 0.1348 | 28.20 | 28.07 | 6.56 |
|
2020-07-28, 13:00 | 3* | 0.1357 | 18.35 | 18.47 | 6.55 |
|
2020-07-29, 06:00 | 4* | 0.1360 | 6.14 | 6.26 | 6.31 |
|
2020-07-27, 14:00 | 5** | 0.1372 | 3.05 | 3.03 | 6.26 | 68.13*** |
* dilution factor for ion chromatographic analysis = 10000
** dilution factor for ion chromatographic analysis = 1000
*** dilution factor for ion chromatographic analysis = 80000
APS decomposes rather quickly under the given test conditions, however significantly slower than at pH = 4. After approx. 48 h less than 10% of the original content was found in the respective samples. The amount of sulfate detected in the terminal sample is in good agreement with that finding. At this temperature, it was also not possible to hold the pH value of the buffered solutions at 7. It drifted steadily to 6.26 throughout the study.
The decomposition of PPS follows a first order kinetic under these conditions. The rate constant (inverse of the trend line’s slope) can be obtained with a satisfactory coefficient of determination of R2 = 98.5 % to a value of k = 0.058 h-1. The respective half-life value was calculated to be 12.0 h.
Half-lives of potassium persulfate at 50 °C as a function of pH were calculated from data in the Kolthoff and Miller report.
pH-value |
1.0 |
1.6 |
3.0 |
7.0 |
10.0 |
Half-life (hours) |
20 |
65 |
120 |
130 |
210 |
DT50 at pH 7: 130 h (5.4 d) at 50 °C = 1929.6 h (80.4) d at 12 °C (Arrhenius equation)
Description of key information
KPS showed minor hydrolysis at 25 °C, which was not continuously, but only towards the end of the monitored timeframe. Whereas at 60 °C strong hydrolysis (faster at acidic than at neutral pH values) was observed. The DT50 at pH 4 and 60 °C was determined to be 7.1 h and at pH 7 and 60 °C the DT50 was determined to be 12 h. The DT50 at environmentally relevant temperature (12 °C) and pH 7 was extrapolated to be 558.3 h (23.3 d).
Key value for chemical safety assessment
- Half-life for hydrolysis:
- 23.3 d
- at the temperature of:
- 12 °C
Additional information
A study according to OECD TG 111 was performed to determine the hydrolysis potential of the test item. Initially, a Tier 1 tests at for 5 days at 50 °C and pH 4, 7 and 9 were performed with the category member APS. Hydrolisys of more than 10 % was observed at all pH levels. Thus, a Tier 2 hydrolysis test was conducted at 10, 25 and 60 °C and pH 4, 7 and 9 with APS. It was shown that the persulfate is hydrolytically stable at 10 °C and different pH-levels, therefore, hydrolysis studies with KPS were performed only at the relevant test conditions. Hydrolysis studies at 25 °C and pH 4 and 60 °C and pH 4 and 7 were conducted with KPS. The test at 25 °C run for ca. 30 days, while at 60 °C the hydrolysis process was finished after 2 - 4 days. KPS showed minor hydrolysis at 25 °C, which was not continuously, but only towards the end of the monitored timeframe. Whereas at 60 °C strong hydrolysis (faster at acidic than at neutral pH values) was observed. The DT50 at pH 4 and 60 °C was determined to be 7.1 h and at pH 7 and 60 °C the DT50 was determined to be 12 h. The DT50 at environmentally relevant temperature (12 °C) and pH 7 was extrapolated to be 558.3 h (23.3 d).
In a disregarded study from 1951 on the hydrolysis of KPS at pH levels from 1 to 10, the rates of decomposition of KPS increased with decreasing pH ranging from 0.035 h-1 at pH 1 to 3.3 h-1 at pH 10, respectively, DT50 of 20 hour to DT50 of 21 hour. The rate of hydrolysis at pH 7 and 12 °C was calculated using the Arrhenius equation resulting in 3.6E-04 h-1 and DT50 = 1929.6 h (80.4 days).
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
