Registration Dossier
Registration Dossier
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EC number: 253-523-3 | CAS number: 37482-11-4
Adsorption / desorption
Administrative data
Link to relevant study record(s)
Description of key information
Log Koc <3: Adsorption to solid soil phase is not expected. For the substance the Koc value is ca. 2 L/kg (log Koc = 0.28) based on the MCI method.
Key value for chemical safety assessment
Additional information
No experimental data on adsorption / desorption is available for sodium 2 -mercaptoethanolate. The 2-mercapthoethanolate ion is a conjugated base, 2-mercaptoethanol (CAS 60-24-2) its undissociated acid. With a pKa value of ca. 9.5 for both substances, in an aqueous environment with pH 7, they will be present almost exclusively as 2-mercaptoethanol. Therefore, consideration of the sorption behaviour of 2-mercaptoethanol (by read-across) is considered most relevant for environmental assessment.
No experimental data on the sorption potentail is available for 2 -mercaptoethanol. Therefore the (log) Koc was estimated with the MCI method of the KOCWIN (v2.00) module of EPISuite (v4.11). For the read-across substance and the target substance the KOCWIN predicted (log) Koc value is identical as the MCI method is based solely on structure (with exclusion of the sodium ion). Also, the MCI method does not differentiate between the -ethanol versus the -ethanolate structural moiety. The Koc is estimated to be ca. 2 L/kg (log Koc = 0.28) for both substances.
No KOCWIN log Kow method predictions were made as no experimental log Kow is available for the sodium 2-mercaptoethanolate. QSAR predictions for the physicochemical properties of the (sodium) 2 -mercaptoethanolate show that the water solubility may be higher than that of 2 -mercaptoethanol but more importantly, the log Kow is likely to be considerably lower than that of 2 -mercaptoethanol. This is supported by the Kow estimation, deduced from its (seperate) solubility in water and octanol. Based thereon, it may be expected that with increasing pH values and consequentially increasing concentrations of 2 -mercaptoethanolate, the adsorption potential will further decrease.
QSAR-disclaimer
In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.
According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.
For the assessment of the substance (Q)SAR results were used for adsorption / desorption. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and therefore the endpoint(s) sufficiently covered and suitable for risk assessment.
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