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Environmental fate & pathways

Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption: screening
Type of information:
other: Expert statement.
Adequacy of study:
key study
Study period:
2012-10-05 - 2012-10-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Expert statement from testing laboratory, which is certificated under GLP compliance.
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))
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))
GLP compliance:
yes (incl. certificate)
Remarks:
The Department of Health of the Government of The United Kingdom
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No surrogate or analogue material was used.
Test temperature:
Not applicable.
Details on study design: HPLC method:
Not applicable.
Analytical monitoring:
not required
Details on sampling:
Not applicable.
Details on matrix:
Not applicable.
Details on test conditions:
Not applicable.
Computational methods:
Not applicable.
Key result
Sample No.:
#1
Type:
Koc
Value:
ca. 20 000 000 000 000 dimensionless
Remarks on result:
other: Estimation by KOCWINv2.00, since experimental investigations are technically not feasible.
Details on results (HPLC method):
Not applicable.
Adsorption and desorption constants:
Not applicable.
Recovery of test material:
Not applicable.
Concentration of test substance at end of adsorption equilibration period:
Not applicable.
Concentration of test substance at end of desorption equilibration period:
Not applicable.
Details on results (Batch equilibrium method):
Not applicable.
Statistics:
Not applicable.

The determination was not carried out using the HPLC screening method, designed to be compatible with Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001 and Method C.19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 as the method was shown not to be applicable.

The HPLC method is not applicable to strong acids. Although the test substance is not an acid, the sulphonate group is the conjugate base to sulphonic acid. When dissolved in a polar solution, the substance will dissociate since it requires an anion exchange column to obtain consistent retention times. The magnesium sulfonate target substance will only dissociate in the presence of strong acids and is not succeptable to dissociation under environmental conditions. Trial injections were attempted on a cyanopropyl (CN) column with a mobile phase of methanol:water (55:45 v/v) but the peak detected varied in the retention time for each injection separately. It can be assumed, that secondary interactions occurred.

Anionic sulphonate components would need to be analyzed at a pH far below the limits of the test (pH 4.5 to 8.5). However, the adsorption coefficient would then be determined for the dissociated organic component and not for the full, nondissociated structure.

Based on this considerations, the adsorption coefficient of the nondissociated test substance can be expected to be significantly higher than the value which would result by a HPLC determination.

KOCWINv2.00 (Sept 2010) revealed a logKoc of 13.3 based on the representative structure. This value was calculated using alkyl chains of 20 carbons and longer (C22, C24) would result in an even higher estimate.

Validity criteria fulfilled:
yes
Remarks:
Waiving strategy based on valid considerations and in accordance to regulatory requirements.
Conclusions:
An experimental investigation is technically not feasible based on the chemical structure and properties of the test substance. The endpoint is waived by an expert statement from a GLP certified testing laboratory.
Executive summary:

The determination was not carried out using the HPLC screening method, designed to be compatible with Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001 and Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 as the method was shown not to be applicable.

The HPLC method is not applicable to strong acids. Although the magnesium sulfonate target substance (CAS 231297-75-9) is not an acid, the sulphonate group is the conjugate base to sulphonic acid. When dissolved in a polar solution, the substance will dissociate since it requires an anion exchange column to obtain consistent retention times. However, under environmental conditions, dissociation of the substance is not possible (only in presence of a strong acid). Trial injections were attempted on a cyanopropyl (CN) column with a mobile phase of methanol:water (55:45 v/v) but the peak detected varied in the retention time for each injection separately. It can be assumed, that secondary interactions occurred.

Anionic sulphonate components would need to be analyzed at a pH far below the limits of the test (pH 4.5 to 8.5). However, the adsorption coefficient would then be determined for the dissociated organic component and not for the full, nondissociated structure.

Based on these considerations, the adsorption coefficient of the nondissociated test substance is expected to be significantly higher than the value which would result by a HPLC determination.

KOCWINv2.00 (Sept 2010) revealed a logKoc of 13.3 based on the representative structure. This value was calculated using alkyl chains of 20 carbons and longer (C22, C24) would result in an even higher estimate.

Description of key information

Experimental procedure is technically not feasible. Prediction with KOCWINv2.00: logKoc: 13.3

Key value for chemical safety assessment

Koc at 20 °C:
20 000 000 000 000

Additional information

The determination was not carried out using the HPLC screening method, designed to be compatible with Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001 and Method C.19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 as the method was shown not to be applicable.

The HPLC method is not applicable to strong acids. Although magnesium sulfonate target substance (CAS 231297-75-9) is not an acid, the sulphonate group is the conjugate base to sulphonic acid. When dissolved in a polar solution, the substance will dissociate since it requires an anion exchange column to obtain consistent retention times. The magnesium sulfonate target substance will only dissociate in the presence of strong acids and is not succeptable to dissociation under environmental conditions. Trial injections were attempted on a cyanopropyl (CN) column with a mobile phase of methanol:water (55:45 v/v) but the peak detected varied in the retention time for each injection separately. It can be assumed, that secondary interactions occurred.

Anionic sulphonate components would need to be analyzed at a pH far below the limits of the test (pH 4.5 to 8.5). However, the adsorption coefficient would then be determined for the dissociated organic component and not for the full, non-dissociated structure.

Based on these considerations, the adsorption coefficient of the non-dissociated test substance is expected to be significantly higher than the value which would result by a HPLC determination.

KOCWINv2.00 (Sept 2010) revealed a logKoc of 13.3 based on the representative structure. This value was calculated using alkyl chains of 20 carbons and longer (C22, C24) would result in an even higher estimate.

[LogKoc: 13.3]

[LogKoc: 13.3]