Propanoic acid, 2-hydroxy-, ammonium salt (1:1), (2S)-

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020-05-25 to 2020-05-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Deviations:

no

GLP compliance:

no

Specific details on test material used for the study:

- Test item: Ammonium-(S)-lactate
- Trade name: PURASAL ® NH/COS
- Batch No.: 1906000773
- CAS No.: 137296-15-2
- EC number: 604-012-2
- Molecular weight: 107.11 g/mol
- Content: ~ 100% (~70% Ammonium lactate, ~30% water)
- Physical state: Light yellow liquid
- Storage conditions: Ambient temperature (10 to 30 °C)
- Expiry date: December 16, 2022

Dissociating properties:

yes

No.:

#1

pKa:

9.1

Temp.:

23 °C

Table 1: Results of the titration of main test I:

Concentration of sodium hydroxide solution	0.1 mol/L
Amount of test item	130.0 mg
Starting volume of the test solution	100 ml
Concentration of test item	0.83 mmolL
Test temperature	23 °C

Volume NaOH / ml	pH	n(A^-) / mmol	n(HA) / mmol	n(HA)/n(A^-)	pKa
3.90	9.05	0.390	0.436	1.117	9.10
3.95	9.06	0.395	0.431	1.090	9.10
4.00	9.07	0.400	0.426	1.064	9.10
4.05	9.09	0.405	0.421	1.039	9.11
4.10	9.10	0.410	0.416	1.014	9.11
4.15	9.12	0.415	0.411	0.990	9.11
4.20	9.13	0.420	0.406	0.966	9.11
4.25	9.14	0.425	0.401	0.943	9.12
4.30	9.16	0.430	0.396	0.920	9.12
4.35	9.17	0.435	0.391	0.898	9.12
Mean value					9.12
Relative standard deviation / %					0.1

Table 2: Results of the titration of main test II:

Concentration of sodium hydroxide solution	0.1 mol/L
Amount of test item	119.0 mg
Starting volume of the test solution	100 ml
Concentration of test item	0.76 mmol/L
Test temperature	23 °C

Volume NaOH / ml	pH	n(A^-) / mmol	n(HA) / mmol	n(HA)/n(A^-)	pKa
3.60	8.98	0.360	0.402	1.117	9.03
3.65	9.00	0.365	0.397	1.088	9.04
3.70	9.02	0.370	0.392	1.060	9.04
3.75	9.03	0.375	0.387	1.033	9.04
3.80	9.05	0.380	0.382	1.006	9.05
3.85	9.06	0.385	0.377	0.980	9.05
3.90	9.08	0.390	0.372	0.954	9.06
3.95	9.09	0.395	0.367	0.930	9.06
4.00	9.11	0.400	0.362	0.906	9.06
4.05	9.12	0.410	0.357	0.882	9.07
Mean value					9.05
Relative standard deviation / %					0.1

Table 3: Results of the titration of main test III:

Concentration of sodium hydroxide solution	0.1 mol/L
Amount of test item	119.0 mg
Starting volume of the test solution	100 ml
Concentration of test item	0.76 mmol/L
Test temperature	23 °C

Volume NaOH / ml	pH	n(A^-) / mmol	n(HA) / mmol	n(HA)/n(A^-)	pKa
3.55	9.01	0.355	0.402	1.131	9.07
3.60	9.03	0.360	0.397	1.101	9.07
3.65	9.04	0.365	0.392	1.073	9.07
3.70	9.06	0.370	0.387	1.045	9.08
3.75	9.07	0.375	0.382	1.017	9.08
3.80	9.09	0.380	0.377	0.991	9.09
3.85	9.11	0.385	0.372	0.965	9.09
3.90	9.12	0.390	0.367	0.940	9.09
3.95	9.14	0.395	0.362	0.915	9.10
4.00	9.15	0.400	0.357	0.891	9.10
Mean value					9.08
Relative standard deviation / %					0.1

Table 4: Summary of the main test

Main test	pKa
I	9.11
II	9.05
III	9.08
Mean value main tests I to III	9.08
Relative standard deviation / %	0.3
pKa	9.1

The mean value of the dissociation constant of the test item was calculated to pK_a= 9.1.

Conclusions:

The mean value of the dissociation constant of the test item was calculated to pKa = 9.1. It was assumed, that the determined pKa in the alkaline range (pKa = 9.1) resulted from the ammonium functionality of the test item.

Executive summary:

In a non-GLP study the dissociation constant of ammonium-(S)-lactate has been determined according to the European Commission Regulation (EC) No. 2017/735. A.25. and according to the OECD test guideline OECD 112 with the titration method. The dissociation constant pKa of the test item in water at 23 °C was determined to 9.1. It was assumed, that the determined pK_a in the alkaline range (pK_a = 9.1) resulted from the ammonium functionality of the test item.

Description of key information

In a non-GLP study the the dissociation constant of ammonium-(S)-lactate has been determined according to the European Commission Regulation (EC) No. 2017/735. A.25. and according to the OECD test guideline OECD 112 with the titration method. The dissociation constant pKa of the test item in water at 23 °C was determined to 9.1.

Key value for chemical safety assessment

pKa at 20°C:

9.1

Additional information

It was assumed, that the determined pK_a in the alkaline range (pK_a = 9.1) resulted from the ammonium functionality of the test item.