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Environmental fate & pathways

Adsorption / desorption

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Administrative data

Endpoint:
adsorption / desorption: screening
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
17.08.2004 to 07.12.2004
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP study performed

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report date:
2004

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 106 (Adsorption - Desorption Using a Batch Equilibrium Method)
Deviations:
yes
Principles of method if other than guideline:
OECD 107 (Octanol/water partition coefficient) could not be completed because the test substance was unstable in water. As an alternative, OECD 105 (Octanol Solubility) was completed to allow for the calculation of the partition coefficient.
OECD 106 (Soil adsorption/desorption) was similarly not performed due to the instability of the test substance in water.
Each test method is described in its ·own section below which details materials, methods
and test results.
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
(1R,2S,5R)-2-isopropyl-5-methylcyclohexyl (2R,5R)-5-hydroxy-1,3-oxathiolane-2-carboxylate
EC Number:
604-569-1
Cas Number:
147126-62-3
Molecular formula:
C14H24O4S
IUPAC Name:
(1R,2S,5R)-2-isopropyl-5-methylcyclohexyl (2R,5R)-5-hydroxy-1,3-oxathiolane-2-carboxylate
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Radiolabelling:
no

Study design

Test temperature:
20.1 °C+- 0.2 °C

HPLC method

Details on study design: HPLC method:
In order to measure the amount of OSME in water in the presence of soil, it was necessary to develop an HPLC method capable of detecting OSME in the presence of organics present in soil. During the course of the method validation, it became clear that the test substance degrades rapidly in the presence of water.
We characterized OSME in acetonitrile, water, and various acetonitrile water mixtures
by HPLC under the following conditions:

HPLC under the following conditions:
• Flow isocratic at 1 ml/min
• Mobile phase: acetonitrile:buffer ( 0.0425% H3P04), 80:20
• Column: Supelcosil LC-18-S, 25 cm, 5 µm pore size
• Injection volume: 20 µL
• UV detector: 220 nm, Equipment Information: UV detector: Gilson Model 111 B
Chromatograms comparing OSME in acetonitrile and in water are shown in the report.

Batch equilibrium or other method

Analytical monitoring:
yes
Details on sampling:
The chromatogram on· the above left is OSME analyzed immediately after dissolution in water. The chromatogram shows a small peak of residual OSME at a retention time of 5.25 minutes. A large group of poorly resolved peaks consisting of OSME breakdown products can be seen between 2 and 3 minutes retention time. OSME was observed to immediately breaks down in water. Based on our dissociation constant measurements (see Section 16 of this report) and other observations we concluded that the test substance in water contains a single weakly acidic group with a pKa of 7.36 ± 0.05. A pKa of this magnitude rules out the presence of a carboxylic acid group in the breakdown products present in water. Such a strongly acidic group would be expected to display a pKa iiJ the range of 4. This suggested that the hydrolysis in water does not involve hydrolysis at the ester group but rather opening of the oxathiolane ring. Such a ring opening would be predicted to give rise to an enolizeable keto group. Such a group would be expected to display a pKa in the range of 7 or 8.
The enolizeable keto groups in, for example, acetoacetone, display a pKa of 8.2, while diacetyl acetone, displays a pKa of 7.4. The keto groups themselves are not acidic (Albert and Serjeant, 1962).
The HPLC chromatograms showed that a complex mixture of several breakdown products form when OSME was dissolved in water, almost immediately on contact. Our attempts to quench the hydrolysis were unsuccessful although it was possible to slow the rate of degradation by dilution in acetonitrile.
Details on matrix:
water and acetonitrile
Details on test conditions:
Evidence of chemical instability of substance during the test? Yes

Results and discussion

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
Our experiments demonstrated that OSME rapidly degraded in water giving rise to an unidentified series of products. Given the difficulty in isolating and quantifying the individual breakdown products, as would be required in order to conduct a soil adsorption/desorption study, we concluded that it was not possible to conduct an OECD Method 106 analysis within the present scope of work.