Sodium (S)-lactate

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

2022-11-15

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:

The test item Sodium (S)-lactate is only available and marketed as concentrated aqueous solution due to the substance's hygroscopic properties. Experimental determination of the melting point of an aqueous solution is not reasonable because the result will be highly influenced by the presence of water. Therefore, the melting point of the test item is estimated by QSAR prediction. Please refer to QPRF/QMRF documentation for detailed information on model suitability.

Qualifier:

according to guideline

Guideline:

other: Guidance on information requirements and chemical safety assessment Chapter R.6: QSARs and grouping of chemicals

Version / remarks:

May 2008

Principles of method if other than guideline:

QSAR prediction using MPBPVP v1.43 of EpiSuite v4.1.

GLP compliance:

no

Type of method:

other: QSAR calculation.

Specific details on test material used for the study:

Canonical: CC(C(=O)[O-])O.[Na+];
Isomeric: C[C@@H](C(=O)[O-])O.[Na+] ;
Stereoisomers do exist. The input of the respective canonical SMILES and isomeric SMILES (see above) for Sodium (S)-lactate and Sodium (R)-lactate all result in identical QSAR predictions. Stereochemistry is not expected to influence melting point predictions for the different lactates.

Melting / freezing pt.:

304.93 °C

Remarks on result:

other: Adapted Joback Method

Melting / freezing pt.:

141.3 °C

Remarks on result:

other: Gold & Ogle Method

Melting / freezing pt.:

223.12 °C

Remarks on result:

other: Mean value

Key result

Melting / freezing pt.:

174.03 °C

Remarks on result:

other: Weighted value used for assessment.

See QPRF/QMRF

Conclusions:

Estimated melting points from MPBPWIN can only be recommended for screening purposes. However, due to the substance’s hygroscopic properties, the test item Sodium (S)-lactate is only available and marketed as aqueous solution and therefore the melting point estimation for the “pure” substance using the MPBPVP methodology is considered adequate for a regulatory conclusion. The estimated melting point for Sodium (S)-lactate is 174.03 °C.

Executive summary:

Crystalline Sodium (S)-lactate has hygroscopic properties and is extremely difficult to isolate. Therefore, the substance is only manufactured and marketed as a concentrated aqueous solution. It can be concluded that the experimental determination of the melting point of an aqueous solution of Sodium (S)-lactate is not representative for the "pure" substance. Therefore, a QSAR estimation using MPBPVP v1.43 of EpiSuite v4.1 is considered to be more practical in this case. The estimated melting point for "pure" Sodium (S)-lactate is 174.03 °C and the substance is considered to be in the applicability domain of the model. MPBPVP methodology is considered adequate for a regulatory conclusion.

Reference 2

Endpoint:

melting point/freezing point

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

Melting / freezing pt.:

-2.2 °C

Atm. press.:

1 atm

Decomposition:

no

Remarks on result:

other: 5 % (w/w) solution of Sodium lactate in water.

Melting / freezing pt.:

-4.1 °C

Atm. press.:

1 atm

Decomposition:

no

Remarks on result:

other: 10 % (w/w) solution of Sodium lactate in water.

Melting / freezing pt.:

-9.7 °C

Atm. press.:

1 atm

Decomposition:

no

Remarks on result:

other: 20 % (w/w) solution of Sodium lactate in water.

Melting / freezing pt.:

-18.2 °C

Atm. press.:

1 atm

Decomposition:

no

Remarks on result:

other: 30 % (w/w) solution of Sodium lactate in water.

Melting / freezing pt.:

-32.5 °C

Atm. press.:

1 atm

Decomposition:

no

Remarks on result:

other: 40 % (w/w) solution of Sodium lactate in water.

A solution more concentrated than those given in the table could not be cryst:allized at temperature higher than -70° C but formed a glassy solid. 50 % Sodium lactate could not be stirred at -35 °C and became solid at about -55 °C. This concentrated solution would perhaps crystallize on long standing at very low temperatures, but it is doubtful if the exact crystallizing temperature could be detected.

Concentration of solution / % (w/w)	Melting point [°C]
5	-2.2
10	-4.1
20	-9.7
30	-18.2
40	-32.5

Conclusions:

The melting point of different concentrated aqueous solutions of Sodium lactate were determined by the freezing temperature method. As a result the following freezing/melting points for the different Sodium lactate concentrations in water were determined:
5 % (w/w) Sodium lactate in water: m.p. = -2.1 °C;
10 % (w/w) Sodium lactate in water: m.p. = -4.1 °C;
20 % (w/w) Sodium lactate in water: m.p. = -9.7 °C;
30 % (w/w) Sodium lactate in water: m.p. = -18.2 °C;
40 % (w/w) Sodium lactate in water: m.p. = -32.5 °C.

Executive summary:

In this experimental study, which is comparable to an OECD 102 (freezing temperature method), the freezing points of different aqueous solutions of Sodium lactate have been determined. Crystalline Sodium lactate is hygroscopic and extremely difficult to isolate, thus only manufactured and marketed as a concentrated aqueous solution.

As a result the following freezing/melting points for the different Sodium lactate concentrations in water were determined:

5 % (w/w) Sodium lactate in water: m.p. = -2.1 °C;

10 % (w/w) Sodium lactate in water: m.p. = -4.1 °C;

20 % (w/w) Sodium lactate in water: m.p. = -9.7 °C;

30 % (w/w) Sodium lactate in water: m.p. = -18.2 °C;

40 % (w/w) Sodium lactate in water: m.p. = -32.5 °C.

This information is used in a read-across approach in the assessment of the target substance.

Description of key information

The QSAR estimation using MPBPVP v1.43 of EpiSuite v4.1 resulted in a melting point of 174.03 °C for Sodium (S)-lactate.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

174.03 °C

Additional information

Crystalline Sodium (S)-lactate has hygroscopic properties and is extremely difficult to isolate. Therefore, the substance is only manufactured and marketed as a concentrated aqueous solution. It can be concluded that the experimental determination of the melting point of an aqueous solution of Sodium-(S)-lactate is not representative for the "pure" substance. Therefore, a QSAR estimation using MPBPVP v1.43 of EpiSuite v4.1 is considered to be more practical in this case. The estimated melting point for "pure" Sodium (S)-lactate is 174.03 °C and the substance is considered to be within the applicability domain of the model. MPBPVP methodology is considered adequate for a regulatory conclusion.

Supporting information for this endpoint can be derived from an experimental study, comparable to an OECD 102 (freezing temperature method), in which the freezing points of different concentrated aqueous solutions of Sodium lactate were determined:

5 % (w/w) Sodium lactate in water: m.p. = -2.1 °C;

10 % (w/w) Sodium lactate in water: m.p. = -4.1 °C;

20 % (w/w) Sodium lactate in water: m.p. = -9.7 °C;

30 % (w/w) Sodium lactate in water: m.p. = -18.2 °C;

40 % (w/w) Sodium lactate in water: m.p. = -32.5 °C;

A solution more concentrated than those show above could not be crystallized at temperatures higher than -70° C but formed a glassy solid. 50 % Sodium lactate could not be stirred at -35 °C and became solid at about -55 °C.

The supporting information is used in a read-across approach in the assessment of the substance to be registered.