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Environmental fate & pathways

Hydrolysis

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Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
28 September 1998 to 2 December 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1999
Report Date:
1999

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
- The pre-test observation period for the hydrolysis was 7 days instead of 5 days. As also in 7 days no significant hydrolysis occurred, it can be assumed that also in 5 days no hydrolysis occurred.
Qualifier:
according to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
- The pre-test observation period for the hydrolysis was 7 days instead of 5 days. As also in 7 days no significant hydrolysis occurred, it can be assumed that also in 5 days no hydrolysis occurred.)
GLP compliance:
yes
Remarks:
according to “The OECD-Principles of Good Laboratory Practice”, OECD Environment Health and Safety Publications. Series on Principles of Good Laboratory Practice and Compliance Monitoring No. 1, Paris 1998

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: crystalline
Details on test material:
- Name of test material (as cited in study report): Guanidine Carbonate Pure
- Substance type: Salt with organic kation and inorganic anion
- Physical state: White crystalline powder
- Analytical purity: 99.7 %
- Impurities: Sulphate ash <0.05 %, heavy metals calculated as lead, <10 ppm (mg/L), iron 1 ppm, lead <1 ppm, arsenic <3 ppm
- Purity test date: 1998-06-09
- Lot/batch No.: 1867 of Agrolinz Melamin GmbH, St.-Peter-Strasse 25, A-4021 Linz
- Expiration date of the lot/batch: Not specified but considered stable under conditions of storage for at least 5 years
- Storage condition of test material: At room temperature in the dark
Radiolabelling:
no

Study design

Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent products: 0, 1.0, 2.0, 3.0, 46.0, 167.5, 171.5 and 171.75 h
- Sampling method: 1 mL solution was taken from the incubation flask and diluted 1 : 10 with deionized water.
- Sampling intervals/times for pH measurements: 0 and 171.5 or 171.75 h
Buffers:
- pH: Nominal 4, 7 and 9; actual at 24 °C 4.10, 7.00 and 8.95; actual at 50 °C 4.06, 6.97 and 8.77
Buffer pH 4: 500 mL 0.1 mol/L potassium hydrogenphthalate (E. Merck, Darmstadt, Germany, Art: 1.04874, purity: >99.9 %) and 4 mL 0.1 mol/L sodium hydroxide (E. Merck, Art: 6498, purity: >99.0 %) filled up to 1000 mL with deionized water.
Buffer pH 7: 500 mL 0.1 mol/L potassium dihydrogenphosphate (E.Merck, Art: 4873, purity: >99.5 %) and 296.3 mL 0.1 mol/L sodium hydroxide filled up to 1000 mL with deionized water.
Buffer pH 9: 500 mL 0.1 mol/L boric acid (E. Merck, Art: 165, purity: >99.8 %) in 0.1 mol/L potassium chloride (E. Merck, Art: 4936, purity: >99.5 %) and 213 mL 0.1 mol/L sodium hydroxide filled up to 1000 mL with deionized water.
Each buffer solution was degassed with helium for ten minutes and kept one hour at the test temperature 50 "C before use. The deionized water was boiled for 15 minutes and kept in a refrigerator before use.

Details on test conditions:
TEST MEDIUM
- Volume used/treatment: 100 mL (in the solely performed) pre-test
- Lighting: The Solutions were kept in the dark.
- Kind and purity of water: Deionised water, boiled for 15 minutes and kept in a refrigerator before use
- Preparation of test medium: In the (solely performed) pre-test portions of 180 mg of the test substance were weighed in flasks and dissolved in about 100 mL of the appropriate buffer to give solutions of 0.01 mol/L as requested by the guidelines.
OTHER TEST CONDITIONS
- Adjustment of pH: The actual pH of the samples (buffer plus test substance) at the begin of the hydrolysis were 4.9, 7.3 and 9.0 instead of the required values of 4.0, 7.0 and 9.0. This shifts were assumed to be caused by the test substance. No corrections were made
Duration of testopen allclose all
Duration:
171.5 h
pH:
4.9
Temp.:
50 °C
Initial conc. measured:
1.77 g/L
Duration:
171.5 h
pH:
7.3
Temp.:
50 °C
Initial conc. measured:
1.79 g/L
Duration:
171.5 h
pH:
9
Temp.:
50 °C
Initial conc. measured:
1.62 g/L
Number of replicates:
One replicate per pH was used in the pre-test and no main test was required.
Positive controls:
no
Negative controls:
no

Results and discussion

Preliminary study:
In none of the buffer solutions at pH 4, 7 and 9 at 50 °C more than 10 % of the test substance hydrolysed within 5 days.
Transformation products:
no
Dissipation DT50 of parent compoundopen allclose all
Key result
pH:
4.06
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
6.97
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Key result
pH:
8.77
Temp.:
25 °C
DT50:
> 1 yr
Type:
(pseudo-)first order (= half-life)
Remarks on result:
hydrolytically stable based on preliminary test
Details on results:
On the basis of the pre-test results and in accordance with the guidances no main test has been performed.

Any other information on results incl. tables

Table 1: Hydrolysis at 50 °C, pH = 4

Duration [h] pH Temperature [°C] Concentration [g/L] Derivation [%] from concentration at 0 h
0 4.88 50.0 1.77 0
1.0 50.0 1.76 -0.4
2.0 50.0 1.56 -11.4
3.0 50.0 1.66 -5.8
46.0 50.0 1.72 -2.6
167.75 49.9 1.69 -4.0
165.75 49.9 1.81 +2.8
171.50 5.00 49.9 1.75 -1.1

At pH 4 the measured concentration after 2 h was 11.4 % lower than the initial concentration. This was however likely to be caused by the deviation of the analytical method and was not a real decrease as can be seen by the concentration values at later times.

Table 2: Hydrolysis at 50 °C, pH = 7

Duration [h] pH Temperature [°C] Concentration [g/L] Derivation [%] from concentration at 0 h
0 4.88 50.0 1.77 0
1.0 50.0 1.76 -0.4
2.0 50.0 1.56 -11.4
3.0 50.0 1.66 -5.8
46.0 50.0 1.72 -2.6
167.75 49.9 1.69 -4.0
165.75 49.9 1.81 +2.8
171.50 5.00 49.9 1.75 -1.1

Table 3: Hydrolysis at 50 °C, pH = 9

Duration [h] pH Temperature [°C] Concentration [g/L] Derivation [%] from concentration at 0 h
0 8.95 50.0 1.62 0
1.0 50.0 1.56 -3.7
2.0 50.0 1.64 +1.1
3.0 50.0 1.58 -2.5
46.0 50.0 1.71 +5.9
171.5 49.9 1.68 +3.8
171.75 9.00 49.9 1.71 +5.8

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
Guanidine carbonate is hydrolytically stable as evidenced in the pre-test.
Executive summary:

Oberascher (1999) investigated the hydrolytic stability of the test item Guanidine carbonate (CAS 593-85-1) study according to the OECD TG 111 protocol. The GLP-study is considered reliable and conclusive for chemical safety assessment and classification purposes.

The pre-test indicated a half-life at 25 °C of more than one year.

Thus no DT50 was determined and the guanidine kation is considered hydrolytically stable under environmental conditions.