L-(+)-lactic acid

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

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:

The QMRF and QPRF for the QSAR calculation are available below (see attached background material).

Qualifier:

according to guideline

Guideline:

other: REACH guidance on information requirements and chemical safety assessment, chapter R.6: QSARs and grouping of chemicals, May 2008.

GLP compliance:

no

Type of method:

other: QSAR calculation, KOCWIN v2.00

Media:

other: organic carbon (simulated, QSAR)

Specific details on test material used for the study:

- Name of test material (as cited in study report): L-(+)-lactic acid; (2S)-2-hydroxypropanoic acid
- SMILES: O=C(O)[C@H](C)O

Radiolabelling:

no

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.

Reference 2

Endpoint:

adsorption / desorption: screening

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Remarks:

GLP compliant guideline study, but with significant deviations from methodology prescribed by the test guidelines (only one reference substance) hence not reliable.

Qualifier:

according to guideline

Guideline:

OECD Guideline 121 (Estimation of the Adsorption Coefficient (Koc) on Soil and on Sewage Sludge using High Performance Liquid Chromatography (HPLC))

Qualifier:

according to guideline

Guideline:

EU Method C.19 (Estimation of the Adsorption Coefficient (KOC) on Soil and Sewage Sludge Using High Performance Liquid Chromatography (HPLC))

GLP compliance:

yes

Type of method:

HPLC estimation method

Media:

other: HPLC column

Specific details on test material used for the study:

Batch No. 0712002519

Radiolabelling:

no

Test temperature:

Column temperature: 35 °C

Details on study design: HPLC method:

EQUIPMENT
- Apparatus: Alliance Separation Module 2695
- Detection system: Dual lambda absorbance detector 2487

MOBILE PHASES
- Type: 30/70 methanol/water (neutral); 30/70 methanol/phosphate buffer (pH 2.0)
- Solutes for dissolving test and reference substances: water (lactic acid); methanol (phenol)

DETERMINATION OF DEAD TIME
- Method: by means of homologous series/by inert substances which are not retained by the column

REFERENCE SUBSTANCES
- Identity: Phenol

DETERMINATION OF RETENTION TIMES
- Quantity of test substance introduced in the column: 10 µl; 209 ng (neutral), 135 ng (pH 2)
- Quantity of reference substances: 10 µl; 100 ng

REPETITIONS
- Number of determinations: all samples were measured in duplicate; controls were injected once

EVALUATION
- Calculation of capacity factors k': Not calculated
- Calculation of retention times: Not given other than in (single) chromatogram run printouts
- Determination of the log Koc value: <1.32 (i.e. < phenol log Koc)

Key result

Type:

Koc

Value:

< 20.9

Type:

log Koc

Value:

< 1.32

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

Conclusions:

Lactic acid log Koc < 1.32.

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.

Description of key information

Both estimated soil organic carbon-water partitioning coefficients indicate that the substance does not has inherently a 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 1L/kg. These QSAR estimations are supported by an experimental study indicating that the KOC of lactic acid is much lower than 20.9.

Key value for chemical safety assessment

Koc at 20 °C:

1