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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:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP study according to EU Method C.19; since HPLC method could not be performed due to ionic interactions between the test substance and the stationary phase of the column, the Koc was calculated using a QSAR
Cross-reference
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))
Deviations:
yes
Remarks:
see comment below
Qualifier:
according to
Guideline:
OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))
Deviations:
yes
Remarks:
see comment below
Principles of method if other than guideline:
The adsorption potential of the substance could not be determined experimentally by the HPLC method due to surface-active properties of the substance leading to interferences with the column. An estimation of the organic carbon-water partitioning coefficient (Koc) by a QSAR method on the basis of the Kow value therefore was being conducted.
GLP compliance:
yes
Type of method:
HPLC estimation method
Media:
soil

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): MXDA/SM ADDUCT
- Physical state: pale yellow viscous liquid
- Analytical purity: not reported
- Impurities (identity and concentrations): not reported
- Composition of test material, percentage of components:
Component 1: 54.9 %
Component 2: 4.7 %
Component 3: 36.4 %
Conponent 4: 4.0 %
- Isomers composition: not reported
- Purity test date: not reported
- Lot/batch No.: PMS-02A
- Expiration date of the lot/batch: not reported
- Stability under test conditions: not reported
- Storage condition of test material: room temperature in the dark, until 12 April 2002, thereafter, room temperature, in the dark, under nitrogen
Radiolabelling:
no

Study design

Test temperature:
not applicable

HPLC method

Details on study design: HPLC method:
An investigative study, injecting samples onto a cyano column at pH 3 and pH 7, concluded that the ionised form of the test substance was not valid for HPLC estimation of the adsorption coefficient. Over the pH range investigated the test material remained in the ionised form. However, the surface chemistry of the stationary phase of the HPLC column altered significantly, with residual free silanol groups being deactivated under acidic conditions. As the test material was retained at pH 7 but eluted at pH 3, it was evident that retention was not due to partitioning but was due to secondary ionic interactions with free silanols. The main determination could not be completed at pH 3 as this exceeded the valid environmental range of the method.

Batch equilibrium or other method

Computational methods:
As the HPLC method was not valid due to ionic interactions with the stationary phase, an estimation of the adsorption coefficient was performed by QSAR calculation. The test material was assigned the chemical class of non-hydrophobic chemicals and the adsorption coefficient calculated using the equation log10 Koc = (0.52 x log10 Kow) + 1.02 = (0.52 x >6.2) + 1.02 = >4.24

Results and discussion

Adsorption coefficient
Type:
Koc
Value:
> 4.24

Results: HPLC method

Details on results (HPLC method):
Not applicable since the HPLC method could not be used due to ionic interactions of the test substance with the stationary phase

Any other information on results incl. tables

Although computer estimations indicated a potential overestimation of the experimental partition coefficient for a number of components, QSAR calculations have been used to estimate the organic carbon-water partition coefficient. The experimental log Kow was >6.2 and this value was usedin the calculation although computational estimations suggested that the partition coefficient had been possibly overestimated due to secondary interactions between the surface active test substance and the analytical column. The high octanol-water partition coefficient was chosen as a worst case option since at pH's found in the environment, the amine groups present on the test material will be ionised. Typically cationic species bind strongly to soil due to partitioning onto organic matter and also ionic interactions with clay particles.

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
The substance was found to be surface active and to interact with the analytical column. The organic carbon-water partitioning coefficient (Koc) of the substance could therefore not be determined by the HPLC method. The Koc was determined by QSAR calculations using the experimentally determined log Kow of >6.2 (calculation with KOCWIN, version 2.0, Syracuse Research Corporation). The calculated log Koc was >4.24 showing that the substance has potential to adsorb to soil and sediment particles under environmental conditions.
Executive summary:

The organic carbon-water partition coefficient (Koc) of the substance MXDA/SM ADDUCT was determined in accordance with EU Method C.19 under GLP. In a preliminary test performed at pH 3 and pH 7, the suitability of a cyano column for the HPLC test was studied. It was demonstrated that the test material was present in an ionised form over the range of tested pH values. The surface chemistry of the stationary phased of the HPLC column altered significantly depending on the pH value, with residual free silanol groups being deactivated under acidic conditions. As the test material was retained at pH 7 but eluted at pH 3, it was evident that retention of the substance was not only due to partitioning but was also due to secondary ionic interactions with free silanols. The main determination of the Koc thus could not be completed at pH 3 as this exceeded the valid environmental range of the method. Since the HPLC method was not valid due to the ionic interactions with the stationary phase, an estimation of the Koc was performed by QSAR calculations using the KOCWIN computational tool (version 2.0, Syracuse Research Corporation). The Koc in the relevant equation for non-hydrophobic substances was based on the Log Kow of the substances by using the following equation: log Koc = (0.52 x log Kow_experimental) + 1.02. Considering the experimental value for the log Kow of >6.2, the value for the organic carbon-water partitioning coefficient was calculated as log Koc >4.24. Although computational estimations may potentially overestimate the Koc, this calculated value was considered as a reasonable worst case estimation given that the substance may occur in an ionised form under environmental pH conditions. This is because the amine groups present on the test substance will be ionised at pH values found in the environment and the cationic species tend to bind strongly to soil due to partitioning onto organic matter or interactions with clay minerals. In conclusion, it can be expected that the substance MXDA/SM ADDUCT has the potential to adsorb to soil and sediment particles under environmental conditions.