Hydrocarbons, C5-rich

Adsorption / desorption

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 and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

This endpoint is adapted in accordance with REACH Annex XI, Section 1.3 (QSAR). Episuite and the KOCWIN models are well documented and commonly used QSARs for predicting the biodegradation potential of chemicals. Constituents within LOA streams fall within the applicability domain of these models and they have been recommended by ECHA in the Information Requirement Guidelines.

Reason / purpose for cross-reference:

(Q)SAR model reporting (QMRF)

Qualifier:

no guideline required

Principles of method if other than guideline:

The Soil Adsorption Coefficient Program (KOCWIN) estimates the soil adsorption coeffiecient (Koc) of organic compounds. Koc can be defined as "the ratio of the amount of chemical adsorbed per unit weight of organic carbon (oc) in the soil or sediment to the concentration of the chemical in solution at equilibrium"; it is represented by the following equation:

Koc =  (µg adsorbed/g organic carbon) / (µg/ml solution)

The units of Koc are typically expressed as either L/kg or ml/g.

Predicted values of Koc are often used in environmental fate assessment because measurement of Koc is expensive. Traditional estimation methods rely upon the octanol/water partition coefficient (log Kow) or related parameters, but the first-order molecular connectivity index (MCI) has been used successfully to predict Koc values for hydrophobic organic compounds. See details in the cross-reference.

Key result

Type:

log Koc

Remarks:

MCI method

Value:

>= 1.5 - <= 2.65 dimensionless

Remarks on result:

other: Result from QSAR prediction. Range based on the measured constituetns in the streams.

Type:

log Koc

Remarks:

Kow method

Value:

>= 1.85 - <= 4.04 dimensionless

Remarks on result:

other: Result from QSAR prediction. Range based on the measured constituents in the streams.

The MCI model outperforms the log Kow model and covers a wider range of chemical structures. Therefore, more weight is given to the MCI-calculated Koc than the log Kow based Koc but both are included for comparison. Details of the constituents and their log Koc values are found in the KOCWIN QMRF/QPRF (see cross-reference).

Conclusions:

The predicted log Koc of constituents of these streams range from 1.5 to 2.65 (MCI method) and from 1.85 to 4.04 (log Kow method). The MCI model outperforms the log Kow model and covers a wider range of chemical structures. Therefore, more weight is given to the MCI-calculated Koc than the log Kow based Koc.

Executive summary:

The log Koc of measured constituents (at equal or above 0.1% w/w) of this category has been predicted using the EPISUITE v4.11 KOCWIN (2017) program, which uses methodology described by Sahljic et al., (1995) and Meylan et al. (1995). The predicted log Koc for this category using the MCI method is 1.5 to 2.65.

Description of key information

This endpoint is adapted in accordance with REACH Annex XI, Section 1.3 (QSAR). The predicted log Koc of measured constituents (at equal or above 0.1% w/w) of this category with KOCWIN and the MCI method ranges from 1.5 to 2.65. It is not feasible to perform adsorption/desorption tests in UVCB streams.

Additional information

The log Koc of measured constituents of this category (at equal or above 0.1% w/w) has been predicted using the EPISUITE v4.11 KOCWIN (2017) program, which uses methodology described by Sahljic et al., (1995) and Meylan et al. (1995). The predicted log Koc of constituents of these streams range from 1.5 to 2.65 (MCI method) and from 1.85 to 4.04 (log Kow method). The MCI model outperforms the log Kow model and covers a wider range of chemical structures. Therefore, more weight is given to the MCI-calculated Koc than the log Kow based Koc.