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EC number: 850-366-8 | CAS number: 98969-19-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 25-03-2020 to 08-05-2020
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Remarks:
- Guideline study performed under GLP. All relevant validity criteria were met.
- Reason / purpose for cross-reference:
- reference to other study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 112 (Dissociation Constants in Water)
- Deviations:
- no
- Qualifier:
- according to guideline
- Guideline:
- other: EU Method A.25. Dissociation Constants in Water
- Version / remarks:
- April 28, 2017
- Deviations:
- no
- GLP compliance:
- yes
- Dissociating properties:
- yes
- pKa:
- 9.82
- Temp.:
- 19.9 °C
- Conclusions:
- The dissociation constant of the test item was determined using the spectroscopic method to be as follows:
pKa = 9.82 at 20 °C
The optical absorbances at 330 nm of all nine test solutions at various pH (from ca. pH 8 to pH 12) prepared from three 1010 mg/L stock solutions were determined and the seven calculated pKa values were calculated. For each stock solution the respective seven calculated pKa were averaged : (i) pKa 9.83 ± 0.05 ; (ii) pKa 9.81 ± 0.09 and (iii) pKa 9.80 ± 0.09. The mean pKa was 9.82. All relevant validity criteria were considered to be met. Under the conditions of this study, the test item was determined to possess an acidic group with a pKa 9.82. - Executive summary:
The dissociation constant of the substance was determined using the spectroscopic method of OECD TG 112 and EU Method A.25 under GLP. Prior to testing the substance was structurally assessed. The pKa value to be determined was for an acidic group. Initially, the titration method was attempted. A test solution of the test item was titrated with standard acid or base, as appropriate with the pKa values to be determined based on the titration curve obtained. During the performance of the titration method, it was noticed that due to low water solubility of the test item the titration method was not the appropriate method to determine dissociation constant. Therefore, it was decided to perform the spectrophotometric method for the determination of the test item pKa values. A 1010 mg/L stock solution of test item was prepared in methanol. Two test solutions (all 1.01 mg/L) were prepared by diluting the stock solution by factor of 1000 with two buffers (pH 2 and pH 12). Blank solutions were prepared by diluting methanol by factor of 1000 with each of the applicable buffer solutions. From each of the test solutions, an absorption spectrum between 200 and 900 nm was recorded with the appropriate reference solution as reference. The pH of each solution (test and reference solution) was measured using a pH meter. The analytical wavelength was chosen from the absorption spectra recorded from the test item for pH 2 and pH 12. From the absorption spectra of the ionized substance and by comparison with the spectra of the non-ionized substance, it was concluded that the difference in optical absorbance is maximal at 330 nm. Hence 330 nm was chosen as the analytical wavelength. The definitive test was performed at a temperature of 19.9 ± 0.1°C. The optical absorbances at 330 nm of all nine test solutions at various pH (from ca. pH 8 to pH 12) prepared from three 1010 mg/L stock solutions were determined and the seven calculated pKa values were calculated. For each stock solution the respective seven calculated pKa were averaged : (i) pKa 9.83 ± 0.05 ; (ii) pKa 9.81 ± 0.09 and (iii) pKa 9.80 ± 0.09. The mean pKa was 9.82. All relevant validity criteria were considered to be met. Under the conditions of this study, the test item was determined to possess an acidic group with a pKa 9.82.
Applicant assessment indicates: the test item would not significantly ionise at environmentally relevant pH 2 to pH 8 (i.e. < 10% ionisation). The test item would be approximately 10% ionised at pH 8.8. Using the Henderson-Hasselbalch equation the substance would be ca. 15% ionized at pH 9.
Within relevant ECHA guidance environmentally relevant pH is considered to be: fresh surface waters: pH 4 to 9, marine environments: stable approximately pH 8, agricultural soils and sewage treatment plant tanks : pH variable between 5.5 and 7.5. However, based on fresh surface waters pH information presented in WaterBase (European Environment Agency (EEA)) and/or information collated and analysed by Blue Frog Scientific Limited (UK), for EU counties and the UK : datapoints ‘n’ = 22242 ; mean pH = 7.76 ; 2xSD range = 6.73 – 8.79 ; with 5th percentile: pH 6.83, lowest 5th percentile for any country: pH 6.57 and/or 95th percentile: pH 8.31. The realistic environmentally relevant pH range for fresh surface waters would be: pH = ca. 6.6 to ca. 8.3. Consequentially, it is considered the test item will not be significantly ionized (>10%) in relevant fresh waters.
Furthermore, when the substance was tested at pH 7 and pH 9 within an available log Pow : HPLC study to OECD TG 117 (2020), the log Pow observed was found to be insignificantly affected by the effects of ionisation between pH 7 and pH 9 (i.e. ± 0.1 log units). Thus, supporting inconsequential levels of ionisation of the substance being observed at up to pH 9.
It is considered that the substance will not significantly ionize (>10%) in all environmentally relevant pHs.
References:
1. WaterBase (https://eea.europa.eu ; European Environment Agency (EEA)) and/or information collated by Blue Frog Scientific Ltd. (UK)
2. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7a: Endpoint Specific Guidance, July 2017)
3. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7b: Endpoint Specific Guidance, June 2017)
4. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7c: Endpoint Specific Guidance, June 2017)
Reference
(1) Assessment of the spectra of the pure molecular species and the pure dissociated species (pure anion)(Spectroscopic Method)
The phenolic group in test item can dissociate. The pKa value to be determined is thus for an acidic group. From the spectra of the ionized substance and by comparison with the spectra of the non-ionized substance, it was concluded that the difference in optical absorbance is maximal at 330 nm. Hence 330 nm was chosen as the analytical wavelength.From the absorbance and the actual pH values, the approximate pKa value was calculated to be 9.97. The test was performed at a temperature of 19.9 ± 0.1°C.
Table 1. Pre-test Absorbance Data
Solution
|
Absorbance for the test solution [units] |
Actual pH |
pH 6 |
0.0126 |
6.03 |
pH 7 |
0.0113 |
7.01 |
pH 8 |
0.0166 |
8.06 |
pH 9 |
0.0279 |
9.01 |
pH 10 |
0.0905 |
9.99 |
pH 11 |
0.1606 |
10.93 |
pH 12 |
0.1648 |
11.99 |
(2) Exact determination of the pKa value(Spectroscopic Method)
The optical absorbances at 330 nm of all nine test solutions and the seven calculated pKa values from three stock solutions were determined.
Table 2. Main test Absorbance Data
Concentration stock [mg/L] |
Absorbance for the test solution [units] |
Actual pH |
pKa value |
1010 |
0.0120 |
8.03 |
- |
0.0463 |
9.42 |
9.82 |
|
0.0548 |
9.60 |
9.86 |
|
0.0719 |
9.79 |
9.80 |
|
0.0785 |
10.00 |
9.91 |
|
0.0991 |
10.19 |
9.78 |
|
0.1079 |
10.40 |
9.81 |
|
0.1140 |
10.60 |
9.86 |
|
0.1326 |
12.00 |
- |
|
1010 |
0.0137 |
8.03 |
- |
0.0465 |
9.40 |
9.81 |
|
0.0533 |
9.61 |
9.90 |
|
0.0721 |
9.79 |
9.79 |
|
0.0747 |
10.00 |
9.96 |
|
0.0963 |
10.19 |
9.80 |
|
0.1088 |
10.38 |
9.73 |
|
0.1158 |
10.57 |
9.72 |
|
0.1301 |
12.00 |
- |
|
1010 |
0.0152 |
8.03 |
- |
0.0459 |
9.41 |
9.85 |
|
0.0560 |
9.62 |
9.88 |
|
0.0718 |
9.80 |
9.82 |
|
0.0811 |
10.02 |
9.90 |
|
0.0982 |
10.19 |
9.79 |
|
0.1088 |
10.38 |
9.76 |
|
0.1195 |
10.59 |
9.63 |
|
0.1310 |
12.00 |
- |
For each stock solution the respective seven calculated pKa were averaged and the standard deviation were calculated (information provided below).
Table 3. Definitive Test - Absorbance Data
Concentration stock [mg/l] |
pKa |
Standard deviation |
1010 |
9.83 |
0.05 |
1010 |
9.81 |
0.09 |
1010 |
9.80 |
0.09 |
|
|
|
Mean |
9.82 |
|
The mean calculated pKa value from the three stock solutions was 9.82.
The test was performed at a temperature of 19.9 ± 0.1°C.
Description of key information
pKa = 9.82 at 20 °C, OECD TG 112, 2020
Further information: the test item would not significantly ionise at environmentally relevant pH 2 to pH 8 (i.e. < 10% ionisation). The test item would be approximately 10% ionised at pH 8.8. Using the Henderson-Hasselbalch equation the substance would be ca. 15% ionized at pH 9. From data within WaterBase (European Environment Agency) database, the realistic environmentally relevant pH range for European fresh surface waters would be: pH = ca. 6.6 to ca. 8.3. Therefore, it is considered that the substance will not significantly ionize (>10%) in all environmentally relevant pHs.
Key value for chemical safety assessment
- pKa at 20°C:
- 9.82
Additional information
Key study : OECD TG 112, 2020 : The dissociation constant of the substance was determined using the spectroscopic method of OECD TG 112 and EU Method A.25 under GLP. Prior to testing the substance was structurally assessed. The pKa value to be determined was for an acidic group. Initially, the titration method was attempted. A test solution of the test item was titrated with standard acid or base, as appropriate with the pKa values to be determined based on the titration curve obtained. During the performance of the titration method, it was noticed that due to low water solubility of the test item the titration method was not the appropriate method to determine dissociation constant. Therefore, it was decided to perform the spectrophotometric method for the determination of the test item pKa values. A 1010 mg/L stock solution of test item was prepared in methanol. Two test solutions (all 1.01 mg/L) were prepared by diluting the stock solution by factor of 1000 with two buffers (pH 2 and pH 12). Blank solutions were prepared by diluting methanol by factor of 1000 with each of the applicable buffer solutions. From each of the test solutions, an absorption spectrum between 200 and 900 nm was recorded with the appropriate reference solution as reference. The pH of each solution (test and reference solution) was measured using a pH meter. The analytical wavelength was chosen from the absorption spectra recorded from the test item for pH 2 and pH 12. From the absorption spectra of the ionized substance and by comparison with the spectra of the non-ionized substance, it was concluded that the difference in optical absorbance is maximal at 330 nm. Hence 330 nm was chosen as the analytical wavelength. The definitive test was performed at a temperature of 19.9 ± 0.1°C. The optical absorbances at 330 nm of all nine test solutions at various pH (from ca. pH 8 to pH 12) prepared from three 1010 mg/L stock solutions were determined and the seven calculated pKa values were calculated. For each stock solution the respective seven calculated pKa were averaged : (i) pKa 9.83 ± 0.05 ; (ii) pKa 9.81 ± 0.09 and (iii) pKa 9.80 ± 0.09. The mean pKa was 9.82. All relevant validity criteria were considered to be met. Under the conditions of this study, the test item was determined to possess an acidic group with a pKa 9.82.
Applicant assessment indicates: the test item would not significantly ionise at environmentally relevant pH 2 to pH 8 (i.e. < 10% ionisation). The test item would be approximately 10% ionised at pH 8.8. Using the Henderson-Hasselbalch equation the substance would be ca. 15% ionized at pH 9.
Within relevant ECHA guidance environmentally relevant pH is considered to be: fresh surface waters: pH 4 to 9, marine environments: stable approximately pH 8, agricultural soils and sewage treatment plant tanks : pH variable between 5.5 and 7.5. However, based on fresh surface waters pH information presented in WaterBase (European Environment Agency (EEA)) and/or information collated and analysed by Blue Frog Scientific Limited (UK), for EU counties and the UK : datapoints ‘n’ = 22242 ; mean pH = 7.76 ; 2xSD range = 6.73 – 8.79 ; with 5th percentile: pH 6.83, lowest 5th percentile for any country: pH 6.57 and/or 95th percentile: pH 8.31. The realistic environmentally relevant pH range for fresh surface waters would be: pH = ca. 6.6 to ca. 8.3. Consequentially, it is considered the test item will not be significantly ionized (>10%) in relevant fresh waters.
Furthermore, when the substance was tested at pH 7 and pH 9 within an available log Pow : HPLC study to OECD TG 117 (2020), the log Pow observed was found to be insignificantly affected by the effects of ionisation between pH 7 and pH 9 (i.e. ± 0.1 log units). Thus, supporting inconsequential levels of ionisation of the substance being observed at up to pH 9.
It is considered that the substance will not significantly ionize (>10%) in all environmentally relevant pHs.
References:
1. WaterBase (https://eea.europa.eu ; European Environment Agency (EEA)) and/or information collated by Blue Frog Scientific Ltd. (UK)
2. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7a: Endpoint Specific Guidance, July 2017)
3. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7b: Endpoint Specific Guidance, June 2017)
4. ECHA Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7c: Endpoint Specific Guidance, June 2017)
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