Dilactide

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low octanol water partition coefficient and the adsorption potential of this substance is related to this parameter

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Type:

Koc

Value:

< 20.9 dimensionless

Type:

log Koc

Value:

< 1.32 dimensionless

Details on results (HPLC method):

Lactic acid eluted before phenol; phenol has a designated log Koc of 1.32. No relevant differences in the results were observed at neutral pH and pH 2.0.

Validity criteria fulfilled:

yes

Remarks:

With only one reference substance, no calibration curve could be established. Therefore, the study is not valid.

Conclusions:

Lactic acid log Koc < 1.32. This result can be adopted for dilactide, in view of its rapid hydrolysis, forming lactic acid.

Executive summary:

The adsorption coefficient (Koc) of lactic acid 93% aq. on soil and on sewage sludge was determined using high performance liquid chromatography (HPLC).

The Koc and log Koc value of the test substance at neutral pH and at pH 2 was < 20.9 and < 1.32, respectively.

This result can be adopted for dilactide, in view of its rapid hydrolysis, forming lactic acid.

 

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reference 3

Endpoint:

adsorption / desorption, other

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Type:

Koc

Value:

ca. 1 L/kg

Remarks on result:

other: The Koc may vary by pH. The estimated value is applicable to the neutral pH range.

Validity criteria fulfilled:

not applicable

Conclusions:

The adsorption/desorption coefficient of lactic acid was estimated to be approximately 1 L/kg using the QSAR model KOCWIN v2.00.

Executive summary:

The adsorption/desorption coefficient of lactic acid was estimated to be approximately 1 L/kg using the QSAR model KOCWIN v2.00.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

No experimental data on dilactide are available. In aqueous environments dilactide rapidly hydrolyses into lactic acid. Therefore, the adsorption/desorption behaviour of dilactide in the environment can be understood in terms of the adsorption/desorption behaviour of lactic acid.

Both estimated soil organic carbon-water partitioning coefficients indicate that lactic acid does not have an inherent high tendency to adsorb onto soil particles, but is more likely to be found in aquatic compartments. The estimated KOC based on the KOW data equals 0.2218 L/kg. The calculated KOC from the molecular connectivity index is 1 L/kg. These QSAR estimations are supported by an experimental study indicating that the KOC of lactic acid is much lower than 20.9.

In addition, the log Kow of dilactide was determined to be 0.4, indicating a very low potential to adsorb to organic carbon. The possibility that adsorption is driven by other factors than lipophilicity (e.g., surface activity, ionizability, cf. Regulation (EU) 2021/979) is assessed as follows: The surface tension of dilactide in water is 70.7 mN/m, thus higher than the cut-off value of 60 mN/m defined in the EU Method A.5 (surface tension). Therefore, dilactide is not surface active. In addition, the adsorption/desorption behaviour of dilactide in the environment can be understood in terms of lactic acid as dilactide decomposes rapidly to lactic acid. With an octanol-water partition coefficient (log Kow) of -0.54 no significant adsorption of lactic acid to organic matter is expected. Furthermore, lactic acid is readily biodegradable. Therefore, the waiving criteria according to Annex VIII, column 2 of section 9.3.1 of the REACH Regulation, as amended by Regulation (EU) 2021/979, are fulfilled. Performance of an adsorption/desorption study is not required.

Key value for chemical safety assessment

Koc at 20 °C:

1