Registration Dossier

Diss Factsheets

Environmental fate & pathways

Hydrolysis

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
from 2009-12-11 to 2009-12-16
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:
13 April 2004
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Version / remarks:
Regulation 440/2008
Deviations:
no
Principles of method if other than guideline:
NA
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
no details given
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were diluted with buffer and water to fit the calibrated range. The pH value if the diluted samples was adjusted to pH 4.5. 2-aminobenzoic acid and then hydrochloric acid solution was added and the solution was thermostated.
Buffers:
All buffers were diluted with ultra-pure water and adjusted with 0.2 M Sodium hydroxide.
pH 4.0: 0.2 M Potassium hydrogen phthalate
pH 7.0: 0.2 M Potassium dihydrogen phosphate
pH 9.0: 0.2 M Boric acid and Potassium chloride
Details on test conditions:
Temperature: 50 °C +/- 0.5 °C
Light and oxygen: the reaction was carried out using a dark thermostat to avoid photolytic effects. Nitrogen was bubbled into the water for 5 minutes before the preparation of the solutions in order to exclude oxygen.

All glassware, water and buffer solutions were sterilised.
Duration:
5 d
pH:
4
Temp.:
50 °C
Initial conc. measured:
ca. 305 mg/L
Duration:
5 d
pH:
7
Temp.:
50 °C
Initial conc. measured:
ca. 381 mg/L
Duration:
5 d
pH:
9
Temp.:
50 °C
Initial conc. measured:
ca. 377 mg/L
Number of replicates:
five
Negative controls:
yes
Remarks:
control buffer
Statistical methods:
Calculation and construction of the calibration curves were carried out using "EXCEL for Windows".
Preliminary study:
The hydrolysis rate of the test item was found to be 47 % at pH 9 and approximately 100 % at pH 4 and 7. For the latter concentrations were below the detection limit after 5 days.
Transformation products:
not measured
% Recovery:
0
pH:
4
Temp.:
50 °C
Duration:
5 d
% Recovery:
0
pH:
7
Temp.:
50 °C
Duration:
5 d
% Recovery:
53
pH:
9
Temp.:
50 °C
Duration:
5 d
Key result
pH:
7
Temp.:
50
DT50:
< 5 d
Type:
not specified

Analysis of Samples

The content of potassium cyanate in the different pH buffer samples was determined at the beginning and the end of hte test periods. Three samples were taken and analysed at the starf of the study. Five samples were taken from five separate tubes of the hydrolysis test and were anaylsed after 120 hours. Sample volume was 1 mL. This was diluted fivefold at the start of the study. At the end of the preliminary test the samples of buffer solution pH 9 were diluted fivefold. The samples of buffer solution pH 4 were analysed without dilution. The samples of buffer solution pH 7 were diluted twofold. One sample was taken from the control vessel anddiluted in the same way as the samples.

Measured data at a temperature of 50 °C at the start and after 120 hours

pH

Sampling time (hour)

Concentration of

potassium cyanate

 (mg/l )

Hydrolysis

(%)

Measured pH

Test vessels

Mean withthe 95% confidence intervals

4

Start

Control buffer

-

4.00

293

305 ± 16.5

-

4.05

316

4.05

306

4.10

120

Control buffer

-

4.05

< LOQ

< LOQ

100

4.42

< LOQ

4.44

< LOQ

4.42

< LOQ

4.44

< LOQ

4.40

7

Start

Control buffer

-

7.00

372

381 ± 10.9

-

7.02

383

7.02

387

7.03

120

Control buffer

-

7.04

< LOQ

< LOQ

100

7.25

< LOQ

7.30

< LOQ

7.28

< LOQ

7.30

< LOQ

7.25

9

Start

Control buffer

-

9.00

390

377 ± 33.1

-

8.98

391

8.98

351

8.99

120

Control buffer

-

8.98

198

198 ± 2.3

47

9.01

204

9.03

197

9.02

201

9.02

193

9.03

 

Validity criteria fulfilled:
yes
Conclusions:
Based on the results of the preliminary test the hydrolysis rate of potassium cyanate was found to be 47 % at pH 9 after 5 days at 50 °C. Hydrolysis rates at pH 4 and pH 7 were approximately 100 %.
Executive summary:

Purpose

The purpose of this study was to evaluate the hydrolysis of potassium cyanate in different pH buffer solutions.

Results:

Based on the results the hydrolysis rate of potassium cyanate was found to be 47 % at pH 9 after 5 days at 50 °C. Hydrolysis rates at pH 4 and pH 7 were approximately 100 %.

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
from 2008-12-02 to 2009-06-26
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: Water solubility (IUCLID5 section 4.8)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: EU Method A.6 (Water Solubility)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
water solubility: 96.4 g/L
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Samples were taken and measured after 2, 4, 7.5, 24 and 30 hours and on days 4, 5, 6 and 7 in order to collect information about the kinetics of hydrolysis.
1.0 mL of the diluted sample was mixed with 1.0 mL of 0.02-molar anthranilic acid and kept at 40 °C for 10 minutes. Then, 2 mL HCl 37% were added, the solution was heated to 100 °C for 1 minute and then left to cool down to room temperature.
Buffers:
Deionised water (conductivity below 0.1 S/cm and TOC below 5 ppm) was used for the test (commercially available doubly distilled water guarantees conductivity as large as 5 µS/cm).
Estimation method (if used):
NA
Details on test conditions:
In a water solubility study also hydrolysis was observed and recorded at 20°C.
Duration:
7 d
Temp.:
20 °C
Initial conc. measured:
97.06 mg/L
Number of replicates:
2 Experiments with different sampling times (one sample each).
Positive controls:
no
Negative controls:
no
Statistical methods:
NA
Preliminary study:
NA
Test performance:
NA
Transformation products:
yes
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
Qualitative analysis of the remaining solution showed presence of ammonia, which could not be detected in a freshly prepared solution of the test item. Literature also describes hydrolysis of cyanates to ammonia and carbon dioxide with time.
Key result
pH:
10
Temp.:
20 °C
DT50:
7 d
Type:
not specified
Other kinetic parameters:
Cyanates decompose in aqueous solutions forming ammonia and carbonate. This process started after the sampling of day three. A DT50 of 7 days could be estimated from the measured concentrations at 20°C. This DT50 corresponds to 13 days at 12°C.

Day

Absorption diluted sample

Concentration in flask

Difference to previous sample

pH

#

310 nm

g/L

%

---

3

0.93045

90.6

---

approx. 10

4

0.79955

78.0

-14.0

approx. 10

5

0.69131

67.5

-13.4

approx. 10

6

0.57957

56.7

-16.0

approx. 10

7

0.47523

46.6

-17.8

approx. 10

 

Validity criteria fulfilled:
not applicable
Conclusions:
Cyanates decompose in aqueous solutions forming ammonia and carbonate. This process started after the sampling of day three. A DT50 of 7 days could be estimated from the measured concentrations at 20°C. This DT50 corresponds to 13 days at 12°C.
Executive summary:

In a water solubility study also hydrolysis was observed and recorded at 20°C. Samples were taken and measured after 2, 4, 7.5, 24 and 30 hours and on days 4, 5, 6 and 7 in order to collect information about the kinetics of hydrolysis. Qualitative analysis of the solution showed presence of ammonia, which could not be detected in a freshly prepared solution of the test item. Literature also describes hydrolysis of cyanates to ammonia and carbon dioxide with time. Cyanates decompose in aqueous solutions forming ammonia and carbonate. This process started after the sampling of day three. A DT50 of 7 days could be estimated from the measured concentrations at 20°C. This DT50 corresponds to 13 days at 12°C.

Description of key information

Based on the results of the preliminary test the hydrolysis rate of potassium cyanate was found to be 47 % at pH 9 after 5 days at 50 °C. Hydrolysis rates at pH 4 and pH 7 were approximately 100 %. From a water solubility study with the structural analogue sodium cyanate a DT50 of 13 d at 12 °C could be extrapolated. this value is used as worst case value in the risk assessment.

Key value for chemical safety assessment

Half-life for hydrolysis:
13 d
at the temperature of:
12 °C

Additional information

In a screening study (Gaal, 2010), the hydrolysis of potassium cyanate in different pH buffer solutions was evaluated. Based on the results of the test, the hydrolysis rate of potassium cyanate was found to be 47 % at pH 9 after 5 days at 50 °C. Hydrolysis rates at pH 4 and pH 7 were approximately 100 %. This finding is supported by the study of Hartley (1983), where it could be shown that potassium cyanate is hydrolyzed to ammonia and potassium bicarbonate.

In a water solubility study with the structural analogue sodium cyanate also hydrolysis was observed and recorded at 20°C. Samples were taken and measured after 2, 4, 7.5, 24 and 30 hours and on days 4, 5, 6 and 7 in order to collect information about the kinetics of hydrolysis. Qualitative analysis of the solution showed presence of ammonia, which could not be detected in a freshly prepared solution of the test item. Literature also describes hydrolysis of cyanates to ammonia and carbon dioxide with time. Cyanates decompose in aqueous solutions forming ammonia and carbonate. This process started after the sampling of day three. A DT50 of 7 days could be estimated from the measured concentrations at 20°C. This DT50 corresponds to 13 days at 12°C.

Taking all available data together a worst case DT50 of 13 d at 12°C could be concluded