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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes (incl. certificate)
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: days 0, 1, 2, 3, 4, and 7
Buffers:
- pH: 4.0, 7.0, and 9.0
- Composition of buffer:
* buffer pH 4.0: citrate, NaOH, HCl (Certipur, Merck, P/N 1.09435)
* buffer pH 7.0: Phosphate buffer, (supplier: Bernd Kraft GmbH, P/N 03086)
* buffer pH 9.0: boric acid, NaOH, KCl (Certipur, Merck, No. 1.09461)
Details on test conditions:
TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 25 ml volumetric flasks

TEST MEDIUM
- Volume used/treatment: 5.258 mg (pH 4.0), 5.260 mg (pH 7.0), and 5.266 mg (pH 9.0) of Dicyandiamid in 25 ml volumetric flasks with either buffer solution of pH 4.0, pH 7.0, or pH 9.0
- test concentration of each test: 2.5 mmol/l

STANDARD SOLUTION IV FOR ANALYSES:
- Standard solution IV a: 5.245 mg dicyandiamide were weighed into a 25 ml volumetric flask, dissolved in water and made up ti volume with water
- Standard solution IV b: 5.337 mg dicyandiamide were weighed into a 25 ml volumetric flask, dissolved in water and made up ti volume with water

BLANKS:
- Blank value of each buffer solution (pH 4.0, 7.0, and 9.0) was determined twice.
- Test solutions pH 4.0, 7.0, and 9.0 were determined sixfold, each, immediately after preparation following the analytical procedure described in section "Details on analytical methods"

DETERMINATION OF THE HYDROLYTICAL STABILITY:
- Immediately after preparation of the test solutions, approx. 10 ml of the test solutions (pH 4.0, 7.0, and 9.0) and 10 ml of the blank buffer solutions (pH 4.0, 7.0, and 9.0) were filled into a suitable lockable amber glass flask and stored in an incubation chamber at 50 °C
- After approx. 24, 48, 72, 96, and 168 h (pH 7.0 additionally after 193 h) an aliquot of each test solution and each buffer blank solution were analysed as described above (two injections each)
Duration:
7 d
pH:
4
Initial conc. measured:
2.5 mmol/L
Duration:
8 d
pH:
7
Initial conc. measured:
2.5 mmol/L
Duration:
7 d
pH:
9
Initial conc. measured:
2.5 mmol/L
Number of replicates:
One replicate per pH
Positive controls:
no
Negative controls:
no
Preliminary study:
The preliminary study according to OECD 111 (non GLP) evidences that dicyandiamide is hydrolytically stable (less than 10 % of the test substance was hydrolysed in 5 days).
Test performance:
No details reported
Transformation products:
not measured
Details on hydrolysis and appearance of transformation product(s):
See Table 1
% Recovery:
86.4
pH:
4
Temp.:
49.1 °C
Duration:
7 d
% Recovery:
100
pH:
7
Temp.:
49.1 °C
Duration:
7 d
% Recovery:
99
pH:
7
Temp.:
49.1 °C
Duration:
8 d
% Recovery:
99.7
pH:
9
Temp.:
49.1 °C
Duration:
7 d
pH:
4
Temp.:
49.1 °C
Hydrolysis rate constant:
0.02 d-1
DT50:
ca. 25 d
Type:
not specified
Other kinetic parameters:
No other kinetic parameters reported
Details on results:
TEST CONDITIONS
- pH, sterility, temperature, and other experimental conditions maintained throughout the study: Yes

Table 1: Hydrolytic Stability of Dicyandiamide at different pH values

Storage time

[h]

c(Dicyandiamide) t = 0

[mg/25 ml]

c(Dicyandiamide)

t = x

[mg/25 ml]

Recovery rate

[%]

pH 4.0

Start

5.258

-

100.01

24

5.258

5.169

98.3

48

5.258

5.085

96.7

72

5.258

4.969

94.5

96

5.258

4.851

92.3

168

5.258

4.543

86.4

pH 7.0

Start

5.260

-

99.91

24

5.260

5.266

100.1

48

5.260

5.257

99.9

72

5.260

5.249

99.8

96

5.260

5.260

100.0

168

5.260

5.836

111.0

193

5.260

5.209

99.0

pH 9.0

Start

5.266

-

100.11

24

5.266

5.264

100.0

48

5.266

5.267

100.0

72

5.266

5.264

100.0

96

5.266

5.265

100.0

168

5.266

5.250

99.7

 

Validity criteria fulfilled:
yes
Conclusions:
As less than 10 % of the test substance is hydrolysed in 5 days, the test substance Dicyandiamid is considered hydrolytically stable.
Executive summary:

A test according to OECD Guideline 111 was perfomed to determine the hydrolytical stability of Dicyandiamid.

A preliminary test was conducted with an initial test concentration of Dicyandiamid of 2.5 mmol/L at pH of 4.0, 7.0 and 9.0 at an average temperature of 49.1 °C (maximum: 49.4 °C; minimum: 48.8°C). Concentrations of Dicyandiamid were measured with HPLC/UV at days 0, 1, 2, 3, 4, and 7.

At pH 7.0 and 9.0 the concentration of Dicyandiamid did not change significantly within 7 days. At pH 4.0 the concentration of Dicyandiamid at day 7 was 86.4 % of the initial concentration. The hydrolyses rate constant at pH 4.0 was therefore 0.01968/d. The concentration of Dicyandiamid after 5 days at pH 4.0 was 92.3 % of the initial concentration.

As less than 10 % of the test substance is hydrolysed in 5 days, in accordance with OECD Guideline 111 no further hydrolysis test have to be perfomed. The test substance Dicyandiamid is considered hydrolytically stable.

Description of key information

A GLP test according to OECD Guideline 111 was performed to determine the hydrolytical stability of Dicyandiamid. 
A preliminary test was conducted with an initial test concentration of Dicyandiamid of 2.5 mmol/L at pH of 4.0, 7.0 and 9.0 at 49.1 °C. Concentrations of Dicyandiamid were measured with HPLC/UV at days 0, 1, 2, 3, 4, and 7.
Dicyandiamide was shown to be hydrolytically stable at pH 4.0, 7.0, and 9.0 at approximately 50 °C.

Key value for chemical safety assessment

Additional information

At pH 7.0 and 9.0 the concentration of Dicyandiamid did not change significantly within 7 days.

At pH 4.0 the concentration of Dicyandiamid at day 7 was 86.4 % of the initial concentration. The hydrolyses rate constant at pH 4.0 was therefore 0.01968/d. The concentration of Dicyandiamid after 5 days at pH 4.0 was 90.5 % of the initial concentration.

As less than 10 % of the test substance is hydrolysed in 5 days, in accordance with OECD Guideline 111 no further hydrolysis tests have to be performed. The test substance Dicyandiamid is considered hydrolytically stable.