Glycine, N-methyl-, N-coco acyl derivs., sodium salts

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

8 Sept 2017 to 24 Jan 2018

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

see deviations.

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

yes

Remarks:

Due to gel formation, no pre-incubation of samples was performed.

GLP compliance:

no

Type of method:

flask method

Water solubility:

42.19 g/L

Conc. based on:

element

Remarks:

Sodium content was measured in solution.

Loading of aqueous phase:

200 g/L

Incubation duration:

1 h

Temp.:

20 °C

pH:

7

Concentration and Solubility Results

Sample 1 (Flask 1) was excluded from final result calculations as the measured concentration varied from replicates 2 and 3 by more than 15%. As samples 2 and 3 showed good replication, sample 1 was considered an outlier.

Flask	Measured Concentration (ug/L)	Dilution faction of acid(matrix matching)	Concentration of samples taking acid addition into account (ug/L)	Dilution factor of samples	Final concentration of samples (ug/L)
2	84341	1.11	93712.2	50	4685611.1
3	81981	1.11	91090.0	50	4554500.0

Average concentration of samples(ug/L)	Concentration of Test material in sample(g/L)	Concentration of Sodium in Test material(g/kg)	Solubility of Sample(g/L)
4620055.6	4.620	109.5	42.19

The measured solubility for Sodium Cocoyl Sarcosinate was 42.19 g/L (%RSD = 2.0).

 

Results Discussion

During the incubation period, Sodium Cocoyl Sarcosinate formed a gel with water over time. As this affected the accuracy and consistency of the ICP-MS analysis, once it was determined that the saturation equilibrium point was achieved, samples of the aqueous phase (free of undissolved solids) were analysed.

 

The protocol states that the difference in the measured concentration of the samples should be

≤15%. A value of 15.9% was recorded, however sample 1 was considered an outlier and excluded due to the low replicate difference between samples 2 and 3 (%RSD = 2.0). Therefore, samples 2 and 3 were used in the final calculation of solubility.

 

No evidence of chemical instability was observed during this study. However, it was noted that the sample forms a stable gel with water, preventing measurement of solubility over an extended time period. Therefore, in this study solubility was determined over a limited time frame.

 

Observation over the short time period of the solubility test conducted in this study did not indicate that solubility of the material is temperature dependent (>3% per °C) and that any observation of such behaviour would in any case be impossible due to the gelling properties of the sample.

 

Within these limitations no temperature dependence was observed.

 

The final conclusion of this study is therefore that Sodium Cocoyl Sarcosinate had on average a solubility of 42.19 g/L in water at 20 °C.

Description of key information

Water solubility is 42.19 g/L at 20 ºC (OECD 105, modified shake flask)

Key value for chemical safety assessment

Water solubility:

42.19 g/L