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REACH

Amides, C8-18 (even numbered) and C18-unsatd., N,N-bis(hydroxyethyl)

EC number: 931-329-6 | CAS number: 68155-07-7

Life Cycle description
Uses advised against

Environmental fate & pathways

Adsorption / desorption

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Administrative data

Link to relevant study record(s)

Reference

Endpoint:: adsorption / desorption: screening
Type of information:: (Q)SAR
Adequacy of study:: key study
Reliability:: 2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:: results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification
Justification for type of information:: QSAR prediction from a well-known and acknowledged tool. See below under ''attached background material section' for methodology and QPRF.
Qualifier:: according to guideline
Guideline:: other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals
Principles of method if other than guideline:: The Koc of the test substance was calculated using the MCI (Molecular Connectivity Index) and Kow based approaches of the KOCWIN v 2.01 program (EPISuite v 4.11). Since the test substance is an UVCB, the Koc values were estimated for individual constituents using SMILES codes as the input parameter.
Computational methods:: The Koc of the test substance was calculated using the MCI (Molecular Connectivity Index) and Kow based approaches of the KOCWIN v 2.01 program (EPISuite v 4.11). Since the test substance is an UVCB, the Koc values were estimated for individual constituents using SMILES codes as the input parameter.
: Key result
Phase system:: other: Estimated
Value:: ca. 292.54 L/kg
Remarks on result:: other: MCI based method
Remarks:: (log Koc: 1 to 3.16)
: Key result
Phase system:: other: Estimated
Value:: ca. 328.33 L/kg
Remarks on result:: other: Kow based method
Remarks:: (log Koc: 0.56 to 3.28)
Validity criteria fulfilled:: not applicable
Conclusions:: The Koc of test substance was estimated using KOCWIN v 2.01 program (EPISuite v 4.11), to be 292.54 L/kg (log Koc=2.47) with MCI method and 328.33 L/kg (log koc=2.52) Log Kow method.
Executive summary:: The soil adsorption and desorption potential (Koc) of the test substance, C8-18 and C18-unsatd. DEA, was estimated using the Molecular Connectivity Index (MCI) and the Log Kow methods of the KOCWIN v 2.01 program (EPISuite v 4.11). Since the test substance is a UVCB, the Koc values were estimated for individual constituents using SMILES codes as the input parameter. Using the MCI and log Kow methods, the predicted Koc values for all the constituents were estimated to range from 10 to 1448 L/kg and 3.66 to 1904 L/kg respectively. The corresponding log Koc values ranged from 1 to 3.16 and 0.56 to 3.28 (US EPA, 2019). This indicates a negligible to moderate adsorption potential (US EPA, 2012). Since not all constituents meet the MW and structural fragment molecular descriptor domain criteria as defined in KOCWIN v 2.01 user guide of EPI Suite TM, the Koc predictions were considered to be less accurate. Given that the constituents are structurally very similar and vary only in the carbon chain length, a weighted average value, which considers the percentage of each constituent in the substance, was calculated to dampen the errors in predictions. The weighted average Koc (log Koc) values were calculated as 292.54 L/kg (log Koc=2.47) and 328.33 L/kg (log Koc=2.52), using the MCI and log Kow methods respectively. Based on the above information, the test substance is expected to have a moderate adsorption potential (US EPA, 2012) to soil and sediment, leading to slow migration to ground water. Overall, the KOC predictions for the test substance using KOCWIN model of EPI Suite TM can be considered to be reliable with moderate confidence.

Description of key information

Key value for chemical safety assessment

Koc at 20 °C:: 292.54

Additional information

The soil adsorption and desorption potential (Koc) of the test substance, C8-18 and C18-unsatd. DEA, was estimated using the Molecular Connectivity Index (MCI) and the Log Kow methods of the KOCWIN v 2.01 program (EPISuite v 4.11). Since the test substance is a UVCB, the Koc values were estimated for individual constituents using SMILES codes as the input parameter. Using the MCI and log Kow methods, the predicted Koc values for all the constituents were estimated to range from 10 to 1448 L/kg and 3.66 to 1904 L/kg respectively. The corresponding log Koc values ranged from 1 to 3.16 and 0.56 to 3.28 (US EPA, 2019). This indicates a negligible to moderate adsorption potential (US EPA, 2012). Since not all constituents meet the MW and structural fragment molecular descriptor domain criteria as defined in KOCWIN v 2.01 user guide of EPI Suite TM, the Koc predictions were considered to be less accurate. Given that the constituents are structurally very similar and vary only in the carbon chain length, a weighted average value, which considers the percentage of each constituent in the substance, was calculated to dampen the errors in predictions. The weighted average Koc (log Koc) values were calculated as 292.54 L/kg (log Koc=2.47) and 328.33 L/kg (log Koc=2.52), using the MCI and log Kow methods respectively. Based on the above information, the test substance is expected to have a moderate adsorption potential (US EPA, 2012) to soil and sediment, leading to slow migration to ground water. Overall, the KOC predictions for the test substance using KOCWIN model of EPI Suite TM can be considered to be reliable with moderate confidence.

The weighted average MCI estimate (Koc = 292.54 L/kg; log Koc = 2.47) was retained for risk assessment purposes as this method is more appropriate for surface active substances.

A supporting study was conducted to determine the adsorption/desorption characteristics of the read across substance, N,N-bis(2-hydroxyethyl)-dodecanamide (abbreviated C12 DEA), according to OECD Guideline 406 (indirect method), in compliance with GLP. The substance was tested in five different soils at 20˚C. Test performance included the determination of: adsorption kinetics, adsorption isotherms (according to Freundlich), desorption kinetics and desorption isotherms (according to Freundlich). Pretests were performed to obtain an optimal soil to solution ratio and to check of the stability of the substance under test conditions (mass balance). Chemical analysis was performed by LC-MS/MS. As initial experiments were performed using unsterile soil conditions and the results indicated a loss of the test substance during the incubation period, subsequent experiments were performed under sterile conditions and a low amount of soil (soil:solution ratio 1:50). The mass balance subsequent to the performance of the adsorption and desorption kinetic experiments was in the range of 80 – 90% for four out of five soils. After an increase of sample size by a factor of 2, mass balance >90% could be established for all 5 soils. Consequently, the isotherm experiments were performed with the scaled-up sample size. The incubation time of 24 h was applied to reach equilibrium conditions. Four (IME-01A, IME-02A, IME-03G and IME-04A) of the five soils were provided. Sorption tests with different concentrations of the test substance were evaluated using the Freundlich equation. The tested concentration ranges were depending on soil and were approximately 55 - 5500 µg/L (soils IME-03G, IME-04A and LUFA 6S) and approximately 8 - 600 µg/L (soil IME-01A and IME-02A). Recovery of test substance from the test system was proved in a separate experiment considering an adsorption time of 23h. For four soils the recoveries were within the range of 90 – 110% and for soil IME-04A a recovery of 89% was determined. The adsorption coefficients (KF) in the adsorption tests varied up to a factor of 10 in a range between 3.7 and 36.8. Normalization to the organic carbon content of the soils results in Koc ads values from 386 to 1127. This indicates that adsorption of the substance depends on the soil organic carbon content, while no dependence on the soil pH was observed. The 1/n values obtained from the adsorption test ranged between 0.73 and 0.79 for four of the five soils. Soil IME-01A showed s lower 1/n value of 0.53. This indicates that the sorption of the substance is mostly linear. Adsorption equilibrium was achieved after 24 h for all soils. The Freundlich adsorption isotherms showed good correlations with correlation coefficients of >0.96 for all soils. Desorption was proven to be almost independent from agitation time for all soils. The correlation coefficients of desorption isotherm are moderate in the range of 0.87 – 0.95. The reason for the moderate R2 values is the low amount of soil applied due to the limited stability of the substance in the test system. 1/n varies in the range of 0.62 to 0.77. Desorption coefficients vary by a factor of 1.5 between 16.7 and 26.8. No correlation between organic carbon content of the soils and desorption could be observed since organic carbon normalized desorption coefficients differ up to a factor of about 4. Also, the soil pH value seemed not to influence the desorption behaviour. Under the conditions of the study, the test substance showed fairly high adsorption and low mobility in soils (Hüben, 2022).

The results of the testing are in line with those obtained from modeling withthe KOCWIN v 2.01 program of EPISuite v 4.11.

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Constituents/Carbon chain length*	Mean/adjusted conc	Mole fraction Xi = (mi/Mi)/∑ (mi/Mi)	Log Koc MCI	Koc (L/kg) MCI	Koc x Xi (MCI)	Domain evaluation
C8	6.0	0.075200289	1	10	0.75	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C10	6.0	0.067068256	1.08	11.9	0.80	MW (ID), Structural fragment ( (Aliphatic Alcohol (-C-OH))
C12	47.5	0.479126606	1.60	39.53	18.94	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C14	17.0	0.156231481	2.12	131.3	20.51	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C16	8.3	0.06962785	2.64	436.1	30.36	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18	7.5	0.058518456	3.16	1448	84.73	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18'	10.0	0.078451053	3.16	1448	113.60	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18''	2.0	0.015776008	3.16	1448	22.84	MW (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
				Koc=	292.54
				Log Koc=	2.47

Constituents/Carbon chain length*	Mean/adjusted conc	Mole fraction Xi = (mi/Mi)/∑ (mi/Mi)	Log Koc (log Kow)	Koc (L/kg) Log Kow	Koc x Xi (Log Kow)	Domain evaluation
C8	6.0	0.075200289	0.56	3.66	0.28	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C10	6.0	0.067068256	1.11	12.76	0.86	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C12	47.5	0.479126606	1.65	45.02	21.57	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C14	17.0	0.156231481	2.20	156.80	24.50	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C16	8.3	0.06962785	2.74	546.40	38.04	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18	7.5	0.058518456	3.28	1904.00	111.42	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18'	10.0	0.078451053	3.16	1457.00	114.30	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
C18''	2.0	0.015776008	3.04	1101.00	17.37	MW (ID), log Kow (ID), Structural fragment (OD) - 1 out of 3 fragments (Aliphatic Alcohol (-C-OH))
				Koc=	328.33
				Log Koc=	2.52