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Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2011-05-26
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP study, but good scientific documentation
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Qualifier:
equivalent or similar to
Guideline:
EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)
Principles of method if other than guideline:
In this study the stability of SIKA Hardener MH in water and in organic solvents (acetonitrile and methanol) was investigated. In order to assess the hydrolysis sampling was performed at representative and relevant points in time. The degradation products of SIKA Hardener MH were identified and the degradation product's stability was investigated in media used for ecotoxicological studies (OECD and ISO medium).
GLP compliance:
no
Remarks:
Non-GLP study, but good scientific documentation
Specific details on test material used for the study:
- Batch no.: 10191-AKm
- Purity: 100.5 %
- Expiry date: 2013-06-16
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
Stock solutions:
- 25 mg/mL SIKA Hardener MH in acetonitrile (for stability test in acetonitrile)
- 25 mg/mL SIKA Hardener MH in methanol (for stability test in methanol)
- 10 mg/mL SIKA Hardener MH in acetonitrile (for stability test in water)
- 1 mg/mL degradation product of SIKA Hardener MH (Aldehyde M) in acetonitrile (for stability test in OECD and ISO medium)

Preparation of working solutions for investigating the stability/hydrolysis via LC/MS and LC/MS/MS, respectively:
- For stability test in organic solvents:
The stock solutions were diluted with methanol or acetonitrile in three steps (25x, 10x, 10x) from 25 mg/mL to 10 µg/mL. The stock solution prepared on methanol was diluted with methanol containing 1mM ammonium formate.
- For stability test in water:
The stock solution (10 mg/mL MH in acetonitrile) was quickly diluted with ultra-pure water in one step from 10 mg/mL to 10 µg/mL and 100 µg/mL, respectively.
- For stability test in OECD and ISO medium:
The stock solutions were diluted to 2.5, 5, 10, 25, 50, 75, 100, 150 ng/mL concentrations with water, ISO or OECD medium.
The protriptyline hydrochloride concentration was 125 ng/mL in each working solutions. Protriptyline hydrochloride was used as internal standard.
Buffers:
- OECD medium: aqueous buffer solution prepared in accordance with OECD guideline no. 201 (Algae), pH = 8.1
- ISO medium: aqueous buffer solution prepared in accordance with OECD guideline no. 202 (Daphnia sp.), pH = 6 - 9
Details on test conditions:
- Solvent: ultra-pure water, acetonitrile and methanol (for SIKA Hardener MH), ultra-pure water, OECD and ISO medium (for Aldehyde M)
- Sampling: immediately after dilution, 0.5 and 1 minutes later (in water); immediately after dilution, 2 and 4 hours later (in acetonitrile); immediately after dilution (in methanol); immediately after dilution, 13 and 26 hours later (in ISO and OECD medium)
- Other:
In order to assess the adsorption of the test item to the vial's surface the stock solution (10 mg/mL SIKA Hardener MH in acetonitrile) was quickly diluted to 10 µg/mL or 100 µg/mL in one step with ultra-pure water. After homogenization the solution was transferred out into another vial. To recover the adsorbed test item the original vial was washed with equal volume of acetonitrile. Then the rinsing acetonitrile was injected directly into the LC/MS system.
Number of replicates:
3 replicates (in OECD and ISO medium for SIKA Hardener MH's degradation product)
Positive controls:
no
Negative controls:
no
Transformation products:
yes
No.:
#1
No.:
#2
Details on hydrolysis and appearance of transformation product(s):
#1 degradation product:
- CAS no.: 23588-51-4
- CAS name: 4-Morpholinepropanal, a,a-dimethyl-
- IUPAC name: 2,2-dimethyl-3-(morpholin-4-yl)propanal
- Common name: Aldehyde M

#2 degradation product:
- CAS: 124-09-4
- CAS name: Hexamethylenediamine
- IUPAC name: 1,6-Hexanediamine
% Recovery:
0
Temp.:
25 °C
Duration:
ca. 0.6 min
Key result
Temp.:
25 °C
DT50:
ca. 0.3 min
Details on results:
Calibration:
Calibration series were prepared from separate stock solutions for Aldehyde M (as reference compound) and for Aldehyde M originated as degradation product from the hydrolysis of SIKA Hardener MH in water, OECD and ISO medium immediately after dilution, 13 and 26 hours later. The concentration of Aldehyde M in these different media showed good linearity in the 2.5 - 150 ng/mL concentration range. The calibration curves were constructed applying linear regression.

Investigation of the hydrolysis of SIKA Hardener MH and identification of its degradation products:

In acetonitrile no degradation products of SIKA Hardener MH (Aldehyde M, m/z: 172.1 amu) could be detected, even after a storage for 24 hours (see Figures 1 - 3). In contrast after mixing SIKA Hardener MH with the protic solvent methanol an intense signal of the degradation product Aldehyde M (m/z: 172.1 amu) and its methanol-adduct (m/z: 204.0) could be observed (see Figure 4). MS spectra of SIKA Hardener MH in ultrapure water at a low concentration level (10 µg/mL) (see Figure 5) showed immediately after dilution an alomost complete hydrolysis. No signals of SIKA Hardener MH (m/z: 423.1 amu for [MH+H+]) could be detected. At the high concentration level (100 µg/mL) (see Figure 6) weak MS signals of SIKA Hardener MH (~ 8 % relative abundance) and intense signals of the degradation products Aldehyde M (m/z: 172.1 amu), its methanol-adduct (m/z: 204.0) and the corresponding amine (m/z: 171.1 amu) could be detected immediately after preparation. The weak signal of the parent compound practically disappeared within approximately 1 minute (see Figure 7, 8).

Furthermore via the analysis of the solvent that was used for washing the vial containing test item solution, it could be shown that the very fast and intense degradation of SIKA Hardener MH is the predominant process resulting in prompt disappearance of the test items in water. Thus the adsorption of the test item on the vial's surface can be excluded.

The degradation products (Aldehyde M and hexandiamine) were identified via their MS signals (m/z: 172.1 amu and m/z: 171.1 amu, respectively) (see Figure 5 - 8).

The storage stability of the degradation product of SIKA Hardener MH (Aldehyde M) was evaluated in aqueous solutions (ultra-pure water, OECD and ISO medium). In ultrapure water (see Figure 9 - 10) Aldehyde M (reference item as well as item originated from the hydrolysis of SIKA Hardener MH) is stable for at least 26 hours. In aqueous buffer solutions (OECD and ISO medium) a rapidly decreasing signal of Aldehyde M (during 26 h storage) was observed (see Figure 11 - 14). In OECD medium approximately 5 times and in ISO medium approximately 1.5 times lower Aldehyde M concentration were measured after 26 hours.

Validity criteria fulfilled:
not specified
Conclusions:
The hydrolysis of SIKA Hardener MH in different media (ultra-pure water, aprotic and protic organic solvents like acetonitrile and methanol) and the stability of SIKA Hardener MH's degradation product (Aldehyde M) in water and aqueous buffer solutions (OECD and ISO medium) at room temperature were investigated using LC/MS and LC/MS/MS, respectively. Measurements revealed a very fast hydrolysis of SIKA Hardener MH in water and water-based media (t1/2 < 0.6 minutes in water). The degradation products of the hydrolysis of SIKA Hardener MH are 2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M) and hexanediamine.
Executive summary:

The hydrolysis of SIKA Hardener MH and the identification of the decomposition products was assessed in a way similar to the methods described in OECD guideline no. 111 and EU method C.7.

The hydrolysis of SIKA Hardener MH in different media (water, aprotic and protic organic solvents like acetonitrile and methanol) and the stability of the degradation product (2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M)) in water and aqueous buffer solutions (OECD and ISO medium) at room temperature was investigated using LC/MS.

Measurements revealed a very fast hydrolysis of SIKA Hardener MH in water and water-based media (t1/2 < 0.6 minutes in water). The degradation products of the hydrolysis of SIKA Hardener MH 2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M) and hexanediamine were successfully identified via their MS signals. In the aprotic organic solvent acetonitrile SIKA Hardener MH is stable for at least 26 hours storage. In contrast in the protic solvent methanol SIKA Hardener MH is not stable.

The storage stability of the degradation product of SIKA Hardener MH (Aldehyde M) was evaluated in aqueous solutions (ultra-pure water, OECD and ISO medium). In ultra-pure water Aldehyde M is stable for at least 26 hours. In aqueous buffer solutions (OECD and ISO medium) a rapidly decreasing signal of Aldehyde M was observed. In OECD medium approximately 5 times and in ISO medium approximately 1.5 times lower Aldehyde M concentration were measured after 26 hours. This observation indicates that the measured concentration of Aldehyde M in these ecotoxicological media does not reflect its real concentration.

Description of key information

The hydrolysis of SIKA Hardener MH in different media (ultra-pure water, aprotic and protic organic solvents like acetonitrile and methanol) and the stability of SIKA Hardener MH's degradation product (Aldehyde M) in water and aqueous buffer solutions (OECD and ISO medium) at room temperature were investigated using LC/MS and LC/MS/MS, respectively. Measurements revealed a very fast hydrolysis of SIKA Hardener MH in water and water-based media (t1/2 < 0.6 minutes in water). The degradation products of the hydrolysis of SIKA Hardener MH are 2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M) and hexanediamine.

Key value for chemical safety assessment

Half-life for hydrolysis:
0.6 min
at the temperature of:
25 °C

Additional information

The hydrolysis of SIKA Hardener MH and the identification of the decomposition products was assessed in a way similar to the methods described in OECD guideline no. 111 and EU method C.7.

The hydrolysis of SIKA Hardener MH in different media (water, aprotic and protic organic solvents like acetonitrile and methanol) and the stability of the degradation product (2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M)) in water and aqueous buffer solutions (OECD and ISO medium) at room temperature was investigated using LC/MS.

Measurements revealed a very fast hydrolysis of SIKA Hardener MH in water and water-based media (t1/2 < 0.6 minutes in water). The degradation products of the hydrolysis of SIKA Hardener MH 2,2-dimethyl-3-(morpholin-4-yl)propanal (Aldehyde M) and hexanediamine were successfully identified via their MS signals. In the aprotic organic solvent acetonitrile SIKA Hardener MH is stable for at least 26 hours storage. In contrast in the protic solvent methanol SIKA Hardener MH is not stable.

The storage stability of the degradation product of SIKA Hardener MH (Aldehyde M) was evaluated in aqueous solutions (ultra-pure water, OECD and ISO medium). In ultra-pure water Aldehyde M is stable for at least 26 hours. In aqueous buffer solutions (OECD and ISO medium) a rapidly decreasing signal of Aldehyde M was observed. In OECD medium approximately 5 times and in ISO medium approximately 1.5 times lower Aldehyde M concentration were measured after 26 hours. This observation indicates that the measured concentration of Aldehyde M in these ecotoxicological media does not reflect its real concentration.