Amines, C16-18 (even numbered)-alkyl , salts with phosphoric acid, mono- and di-C16-18 (even numbered) alkyl esters

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

yes

Remarks:

For the analysis of C16H33NH2 at the sampling time #4 & #5, the recovery rate of the quality controls was lower the acceptability range of 80-20% (i.e. 64 and 68%). This deviation was not considered to have affected the outcome of the study.

GLP compliance:

yes (incl. QA statement)

Type of method:

column elution method

Water solubility:

< 0.248 mg/L

Conc. based on:

act. ingr.

Loading of aqueous phase:

496 mg/L

Incubation duration:

ca. 113 h

Temp.:

20 °C

pH:

4

Remarks on result:

not determinable

Remarks:

Both primary amines were not detected in samples after around 113h of test item exposition to ultra-pure water.

Key result

Water solubility:

< 0.031 mg/L

Conc. based on:

act. ingr.

Loading of aqueous phase:

496 mg/L

Incubation duration:

ca. 113 h

Temp.:

20 °C

pH:

4

Remarks on result:

not determinable

Remarks:

Both primary amines were not detected in samples after around 113h of test item exposition to ultra-pure water.

Details on results:

Test item concentrations determined in all samples are presented as follows and attached in background document :

- Table 1 Test item determinations: C16H33NH2, flow rate 25 mL/h
- Table 2 Test item determinations: C16H33NH2, flow rate 12.5 mL/h
- Table 3 Test item determinations: C18H37NH2, flow rate 25 mL/h
- Table 4 Test item determinations: C18H37NH2, flow rate 12.5 mL/h

Conclusions:

The water solubility of the test item at 20°C was determined as follows:

- C16H33NH2 < LD (i.e. 0.031 mg/L)
- C18H37NH2 < LD (i.e. 0.248 mg/L)

Executive summary:

The water solubility of Amines, C16-18 (even numbered)-alkyl , salts with phosphoric acid, mono- and di-C16-18 (even numbered) alkyl esters was determined according to the OECD 105 guideline (column method) and GLP.

 

Due to the complexity of the test item composition (multi-constituant with presence of saturated and unsaturated primary amines as well as alcohols, mono and di ester phosphoric distribution), the sponsor requested the analysis to be performed on the primary amines C₁₆H₃₃NH₂ and C₁₈H₃₇NH₂.

 

As recommended in the test guideline, two runs were performed, the second one at half the flow rate of the first.

 

Both primary amines were not detected in samples throughout the whole test period, the water solubility of the test item is thus determined as follows:

 

• primary amine C16:0 : C₁₆H₃₃NH₂ < LD (i.e. 0.031 mg/L)


• primary amine C18:0 : C₁₈H₃₇NH₂ < LD (i.e. 0.248 mg/L)

 

Description of key information

The water solubility of the test item was determined according to the OECD 105 guideline and GLP. Primary amines were not detected < LD mg/L therefore this result on the whole salt is in coherence with the calculated result obtained on alkylamines C16-C18 alone (calculated value of 7.89 x 10-4 mg/L). In a worst-case approach, the solubility of the Alkyl phosphate and stearyl amine salt (EC = 952-252-4) was considered as driven by the properties of the alkylammonium part. 

Key value for chemical safety assessment

Water solubility:

0.03 mg/L

at the temperature of:

20 °C

Additional information

Alkyl phosphate and stearyl amine salts (EC = 952-252-4) is a multi-constituent manufactured as a solid block. The registered substance is mainly composed by primary alkylamines (CAS 90640-32-7, UVCB), Monoalkyl dihydrogenophosphate and Dialkyl hydrogenophosphate salts (CAS 39471-52-8, Multi-Constituant). This different chemical structures are constituted by saturated and variable chain lenght with C16 and C18.

 

N-hydrogenated tallow alkyl amine (CAS 90640-32-7) among which C16 and C18 n-alkylamines are one of the major constituents. Primary fatty amines in their free (non-protonated) form are very poorly soluble in water.

 

Measurements must be performed at very high pH (pKa 10.6) and due to the very low concentrations experimental determination is often technically not possible. Therefore, values given in Table 1 below are calculated with the exception of C12-, C14- and C16-alylamines. Calculation for the remaining compounds was performed based on their C-Chain distribution according to the formula presented in the publication by Matuura et.al. [1]. As would be expected, a clear trend of decreasing water solubility with increasing chain length is obvious:

Table 1: water solubilities of the commercial substances derived from the water solubilities of the C-chain pure amines (unprotonated).

 

Substance Name	solubility [mg/L]
Dodecan-1-amine	3.70
Tetradecan-1-amine	0.213
Hexadecan-1-amine	1.08 x 10-2
C12-18-(even numbered)-alkylamine	4.63 x 10-3
C16-18-(even numbered, C18 unsaturated)-alkylamine	7.89 x 10-4
C16-18-(even numbered)-alkylamine	7.98 x 10-4
(Z)-Octadec-9-enylamine	6.20 x 10-4
Octadecan-1-amine	5.59 x 10-4

 

Because of their high pKa-values (10.6, i.e. strong bases), at environmentally relevant pH these compounds are fully protonated (99.98% at pH7), i.e. present as alkylammonium-ions.

 

While determining the water solubility of the alkylamine hydrochlorides, a further difficulty is their surface active property: single hydrated molecules are found up to their respective critical micelle concentration (CMC), only. At higher concentrations, molecules will be aggregating to from micelles. Therefore, as a substitute of the water solubility, the CMC is used for surface active compounds. As will be obvious from the following data table, there is a clear decreasing trend for water solubility with increasing hydrocarbon chain legth, as would be expected:

Table 2: Water solubilities of the commercial substances derived from the water solubilities of the hydrochlorides of the C-chain pure amines (protonated form of amine)

 

Substance Name	solubility [mg/L]
Dodecan-1-amine	3.5 x 103
Tetradecan-1-amine	6.9 x 102
Hexadecan-1-amine	6.3x 101
Octadecan-1-amine	1.3 x 101
(Z)-Octadec-9-enylamine	3.8 x 101

 

Conclusion :

 

Regarding the other main constituents, the Phosphoric acid, octadecyl ester (CAS 39471-52-8), has a water solubility less than < 0.162 mg/L at 20°C according an TG OECD 105. To assess the solubility of Alkyl phosphate and stearyl amine salts (EC = 952-252-4) it is of importance to consider the most conservative reliable values found for each endpoint. The water solubility of the registered test item (EC = 952-252-4) was determined according to the OECD 105 guideline (column method) and GLP. Due to the complexity of the test item composition (multi-constituent), the analytical measurements were performed on the primary amines C16 and C18. Both primary amines were not detected in samples throughout the whole test period, the water solubility of the test item is thus determined as follows:

 

primary amine C16:0 : C16H33NH2 < LD (i.e. 0.031 mg/L)
primary amine C18:0 : C18H37NH2 < LD (i.e. 0.248 mg/L)

 

Therefore the key value for the Chemical Safety Assessment is a solubility < 0.031 mg/L at 20°C.

 

This solubility obtained on the test performed on the whole salt is in coherence with the result obtained on Amines, C16-18-alkyl calculated alone (calculated solubility of 7.89 x 10-4 mg/L). In a worst case approach, the environmental fate (e-fate) and ecotoxicity of the Alkyl phosphate and stearyl amine salts (EC = 952-252-4) was considered as driven by the properties of the alkylammonium part.