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Adsorption / desorption

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Reference
Endpoint:
adsorption / desorption
Remarks:
adsorption
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study conducted in accordance with generally accepted scientific principles, possibly with incomplete or methodological deficiencies, which do not affect the quality of relevant results.
Justification for type of information:
QSAR prediction
Qualifier:
no guideline followed
Principles of method if other than guideline:
No determination of the adsorption coefficient was possible by the HPLC screening method, Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, as the method is not valid for organic acids. A QSAR was conducted instead
GLP compliance:
no
Type of method:
other: No determination of the adsorption coefficient was possible by the HPLC screening method, Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, as the method is not valid for organic acids therefore a QSAR was used instead.
Media:
other: A QSAR was conducted
Specific details on test material used for the study:
SMILES : C(O)C(O)C(O)C(O)C(O[Na])C(=O)O[Fe](OC(=O)(C(C(C(C(CO)O)O)O)O[Na]))(OC(=O)(C(C(C(C(CO)O)O)O)O[Na]))
CHEM : iron(3+) ion trisodium tris(3,4,5,6-tetrahydroxy-2-oxidohexanoate)
MOL FOR: C18 H30 O21 Na3 Fe1
MOL WT : 707.24
Radiolabelling:
no
Test temperature:
Room temperature
Details on study design: HPLC method:
The method is not valid for organic acids. Therefore in place of experimental data, an estimate of the adsorption coefficient was obtained by calculation using Quantitative Structure Activity Relationships (QSAR’s), the details of which are provided in the technical guidance documents in support of Commission Directive 93/67/EEC on risk assessment for new substances.
Analytical monitoring:
no
Computational methods:
The adsorption coefficient of the test item components was estimated using a computer-based atom fragment contribution method, KOCWIN, version 2.00 (September 2010), © 2000-2008 US Environmental Protection Agency. The calculation was performed using the estimated partition coefficient value (log10 Pow) of -19.91 (KOWWIN v.1.68).
Type:
log Koc
Value:
-11.37
Temp.:
20 °C
Remarks on result:
other: % organic carbon was not stated
Details on results (HPLC method):
HPLC method was found to be not suitable for organic acids.
Therefore a QSAR estimate was used instead using KOCWIN which is included in EPIsuite. The fragment constant method (MCI) was not used
Because this method can no calculate the Koc with metals in the structure.

KOCWIN v2.00 Results:
                KOCWIN Program (v2.00) Results:
==============================
SMILES : C(O)C(O)C(O)C(O)C(O[Na])C(=O)O[Fe](OC(=O)(C(C(C(C(CO)O)O)O)O[Na]))(OC(=O)(C(C(C(C(CO)O)O)O)O[Na]))
CHEM  : iron(3+) ion trisodium tris(3,4,5,6-tetrahydroxy-2-oxidohexanoate)
MOL FOR: C18 H30 O21 Na3 Fe1
MOL WT : 707.24
--------------------------- KOCWIN v2.00 Results ---------------------------
NOTE: METAL (Na, Li or K) are REMOVED TO ALLOW ESTIMATION via MCI!

 Koc Estimate from Log Kow:
 -------------------------
        Log Kow (Kowwin estimate) ......................... :-19.91
        Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... :-10.0877
        Fragment Correction(s):
                 2  Aliphatic Alcohol (-C-OH) ........... : -0.8229
                 2  Misc (C=O) Group (aliphatic attach).... : -0.4586
        Corrected Log Koc .................................. :-11.3692
 
                        Estimated Koc: 4.274e-012 L/kg  <===========
Adsorption and desorption constants:
Estimated Koc: 4.274e-012 L/kg
Log Koc = -11.36

The calculated adsorption coefficient (log10 Koc) of (Gluconate)3 -FeNa3 was calculated to be -11.37.

Discussion:

The dissociation constants of the acidic functional groups were estimated to be 3.35 (ACD/Labs I-Lab 2.0). Subsequently, as this values of dissociation constant was less than 4.5; 10% or greater of the unionized form of the test item cannot be achieved within the environmentally relevant pH range of 5.5 to 7.5. Therefore as the unionized form of the test item is not of environmental relevance, and the HPLC estimation method is invalid for the ionised form of the acidic functional group, the adsorption coefficient of the test item was estimated using a QSAR technique.

Validity criteria fulfilled:
not applicable
Conclusions:
Using a QSAR calculation, the adsorption coefficient (log10 Koc) of the test item was estimated to be -11.37.
Executive summary:

Adsorption Coefficient:

No determination of the adsorption coefficient was possible by the HPLC screening method, Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, as the method is not valid for organic acids. Using a QSAR calculation (based on the estimated partition coefficient), the adsorption coefficient of the test item was calculated to be log10 Koc -11.37

Description of key information

Based on expirience from Sodium glucoheptonate (CAS no 31138 -65 -5) no attempt has been made to quantify the Koc of (Gluconate)3 -FeNa3 using the OECD 121 method. Determination of the adsorption coefficient was not possible by the HPLC screening method, Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, as the method is not valid for organic acids.

Using a QSAR calculation (based on the estimated partition coefficient), the adsorption coefficient of the test item was calculated to be log10 Koc -11.37.

Key value for chemical safety assessment

Koc at 20 °C:
0

Additional information

No determination of the adsorption coefficient was possible by the HPLC screening method, Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001, as the method is not valid for organic acids.

In place of experimental data, an estimate of the adsorption coefficient was obtained by calculation using Quantitative Structure Activity Relationships (QSAR’s). Using a QSAR calculation (based on the estimated partition coefficient), the adsorption coefficient of the test item was calculated to be log10 Koc -11.37 (Koc 4.27e-12).

[LogKoc: -11.37]