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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
02-06-2017 to 01-09-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
The competent authority (RIVM and USEPA) have indicated there are concerns with regards to the persistency of the test substance due to conflicting data of biodegradations studies. Therefore the hydrolysis products of 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane have been investigated. Previous studies with organic peroxides have shown them to be influenced by organic matter in the form of Humic acid. Replicates with sterilized natural water and deionized water with humic acid were therefore also investigated.
Sterilised aqueous buffer solutions and test media were spiked with the test substance and incubated (at 12°C) in the dark under controlled laboratory conditions. After appropriate time intervals, buffer solution/test media were analysed to try to identify and quantify the formed hydrolysis products.
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Version / remarks:
Tier 3
Deviations:
yes
Remarks:
see Principles of method if other than guideline
Principles of method if other than guideline:
There were four modifications to OECD guideline 111:
· No thymol was added to the buffer solutions as, based on microbiological experience, the addition of
thymol as a disinfectant is not necessary because the buffer solutions were sterilized also.
· Test temperature of 12 °C was used. As it was the goal to determine the hydrolysis products at
environmental relevant temperatures.
· In addition to the standard OECD guideline buffers, a natural surface water and demineralized water
containing humic acid was tested. The test was performed above the water solubility, this was
necessary to ensure that sufficient hydrolysis product would be generated, to make identification and
quantification possible.
· Test was conducted using techniques not readily available in contract laboratories and was therefore
not conducted to GLP.
GLP compliance:
yes
Radiolabelling:
no
Analytical monitoring:
yes
Buffers:
Buffer solutions were prepared according to the buffer systems as described in Annex 3 of OECD
guideline 111 (OECD, 2004).
Details on test conditions:
De-ionised water
The de-ionised water used in the study contained less than 10 μg/L of copper (not measured under
GLP), with a conductivity of less than 5 μS/cm and less than 2.0 mg/L NPOC-content.

Materials
Test vessels, buffer solution and test media were sterilised. Test solutions were flushed with nitrogen to
minimise oxidation. Test vessels were kept under dark conditions. A temperature-controlled water bath
was used; temperature was measured using a calibrated thermometer, pH was measured using a pH
meter. The pH buffer 7 was made according to the description of Clak and Lubs, described in Annex 3
of OECD 111 (OECD, 2004). The natural surface water was sampled in the Netherlands

Identification of hydrolysis products (Tier 3)
The sterilised buffer solution pH 7, the surface water and demineralized water containing humic acid
were transferred to volumetric flaks and purged with nitrogen for at least 5 minutes.
A stock solution of the test substance was prepared in dichloromethane and spiked to the buffer
solution and the two other media. The solutions were spiked in 50 mL volumetric flasks at a
concentration of approximately 25 mg/L, not exceeding 1 % (v/v) of solvent. Subsequently 10 mL of the
spiked solutions was transferred to multiple sterile glass test vials. The vials were closed tightly and
placed in a thermostatically controlled water bath in the dark at a temperature of 12 ± 0.5°C. At the
moment the test vials were placed in the water bath, the first sample was taken and analyzed using the
analytical methods described in annex 3. Subsequent samples were taken on different time intervals
and analyzed to determine which and the amount of hydrolysis products formed. Samples were
analyzed directly after sampling in order to prevent further hydrolysis and/or thermal decomposition. In
order to ensure that sufficient hydrolysis product would be generated, to make quantification possible,
the water solubility limit was exceeded.
Duration:
90 d
pH:
7
Temp.:
12 °C
Transformation products:
no
Remarks:
no expected or unknown transformation products were seen to increase in concentration during the course of the study
Details on hydrolysis and appearance of transformation product(s):
At the start of the test, next to the test substance, the following products were already percent; MEK (methyl ethyl ketone), acetic acid and MEK type 3. These products are also the expected hydrolysis products. The concentrations of these products were followed during the course of this study, however as the concentrations of these products did not increase significantly, supported by the lack of new products being formed and the Trigonox 301 concentration not decreasing significantly, it was concluded that no hydrolysis products were formed during the 90 day test period at 12 °C.
pH:
7
Temp.:
12 °C
DT50:
> 90 d
Remarks on result:
hydrolytically stable based on preliminary test
Validity criteria fulfilled:
yes
Remarks:
Test temperatures were measured to be within the criteria (12.0 +/- 0.5 oC); the pH value of the buffer pH 7 was measured to be within the criteria (7 +/- 0.1)
Conclusions:
Existing hydrolysis data was brought into question due to the lack of biodegradation and the discrepancies between the test substance and its analogues. Due to this data being critical to the
interpretation of the persistence of the test material an environmentally relevant data point showing apparent rapid hydrolysis in existing data (Harlan 2014) was selected for a repeat and identification of hydrolysis products.
The purpose of this study was to determine the hydrolysis products of 3,6,9-triethyl-3,6,9-trimethyl- 1,4,7-triperoxonane at pH 7 , according to Tier 3 of OECD Guideline No. 111, at a single
environmentally relevant temperature. In addition to the standard buffer solution, the hydrolysis products were also determined in media containing organic material as this has for some peroxide
groups influenced stability. No significant increase in hydrolysis products were detected during the course of this 90 day study. The presence of organic material, addition of an iron complex or elevating the temperature had no effect on the stability of the test substance.
Executive summary:

No significant increase in hydrolysis products were detected during the course of this 90 day study. The presence of organic material, addition of an iron complex or elevating the temperature had no effect on the stability of the test substance.

Description of key information

The results of an OECD 111 Tier 3 test indicate that at a pH value of 7, the half-life (t½) for 3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane at a temperature of 12°C was > 90 days.

Key value for chemical safety assessment

Additional information