Hydroxyoctadecanoic acid, monoester with glycerol

Water solubility

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

March-April 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: OECD 301B

Version / remarks:

Ready Biodegradability: CO2 Evolution (Modified Sturm Test)

Qualifier:

according to guideline

Guideline:

other: International Standards Organisation (ISO) 10634, 1995. Guideline for the preparation and treatment of Poorly Water-Soluble organic compounds for the subsequent evaluation of their biodegradability in aqueous medium.

Principles of method if other than guideline:

Various methods were used to maximize the amount of test material in deionised water.

GLP compliance:

yes

Type of method:

other: high shear method

Key result

Water solubility:

< 50 mg/L

Conc. based on:

test mat.

Temp.:

25 °C

pH:

7.4

Remarks on result:

other: not soluble in water

Details on results:

The following preliminary solubility/dispersibility work was performed in order to determine the most suitable method of preparation:

i) Ultrasonication: A nominal amount of test item (50 mg) was dispersed in 1 liter of deionized reverse osmosis purified water with the aid of shaking by hand for approximately 1 minute prior to ultrasonication for 30 minutes. This formed a clear colorless water column with particles and chunks of test item visible dispersed throughout.

ii) High Shear Mixing: A nominal amount of test item (50 mg) was dispersed in 1 liter of deionized reverse osmosis water and subjected to high shear mixing (approximately 7500 rpm, 30 minutes) and formed a slightly cloudy dispersion with many fine particles of test item visible dispersed throughout and a layer of foam on the surface.

This work confirmed that the test item was insoluble in water. Therefore the following additional solubility work was conducted to ascertain the best method to employ in the biodegradation test.

iii) Ultrasonication: A nominal amount of test item (50 mg) was dispersed in 400 mL of mineral media with the aid of ultrasonication for 15 minutes. The volume was then adjusted to a final volume of 3 liters with mineral media. This formed a clear colorless media column with chunks of test item visible on surface and at bottom of flask.

iv) High Shear Mixing: A nominal amount of test item (50 mg) was dispersed in 400 mL of mineral media with the aid of high shear mixing (approximately 7500 rpm, for 15 minutes). The volume was then adjusted to a final volume of 3 liters with mineral media. This formed a clear colorless media column with an oily layer of test item visible on the surface with a thin layer of foam. After 48 and 72 hours of magnetic stirring a cloudy dispersion was formed with many particles/globules of test item visible on the surface and dispersed throughout.

v) Preliminary Solution in a Volatile Solvent: The addition of a test item solvent stock to glass fibre filter paper was attempted. A nominal amount of test item (1000 mg) was dissolved in chloroform (10 mL) with the aid of ultrasonication for 2 minutes and formed a clear colorless solution. An aliquot (450 µL) of this solvent stock solution was dispensed to filter paper. The solvent was allowed to evaporate to dryness for approximately 15 minutes. The filter paper was then added to approximately 400 mL mineral medium and subjected to high shear mixing (approximately 7500 rpm, 5 minutes). The volume was then adjusted to 3 liters with mineral medium. This formed a cloudy dispersion with an oily layer of test item visible on the surface with a thin layer of foam. Particles of test item/filter paper were visible dispersed throughout. After 48 and 72 hours of magnetic stirring a very cloudy dispersion was formed with many particles/globules of test item visible on the surface and dispersed throughout. Particles of test item/filter paper were visible dispersed throughout.

vi) Preliminary Solution in a Non-Volatile, Non-Degradable Solvent: A nominal amount of test item (100 mg) was dispersed in silicone oil (10 mL) with the aid of shaking by hand for approximately 1 minute followed by ultrasonication for 15 minutes. A clear colorless solvent was formed with chucks of test item visible.

From the preliminary solubility work and following the recommendations of the International Standards Organisation (ISO 10634, (1995)) it was concluded that the best testable dispersion was found to be obtained when using the high shear mixing method of preparation (method iv).

The water solubility of the test material is substantially less than 50 mg/L.

Conclusions:

The water solubility of the test material was assessed using various methods including ultrasonication and high shear mixing, in preparation for a biodegradability study. It was found that solubility in deionized water was considerably less than 50 mg/L due to the presence of chunks and particles of test material. The conclusion of the study is that the substance is not soluble in water, or is consistent with "poorly water-soluble".

Reference 2

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

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

Qualifier:

no guideline followed

Principles of method if other than guideline:

QSAR model

GLP compliance:

no

Type of method:

other: structural analysis

Specific details on test material used for the study:

No test material used.
CAS Number: 1323-42-8
SMILES : O=C(OC(CO)CO)C(O)CCCCCCCCCCCCCCCC
CHEM : Octadecanoic acid, hydroxy-, monoester with 1,2,3-propanetriol
MOL FOR: C21 H42 O5
MOL WT : 374.57

Key result

Water solubility:

0.647 mg/L

Conc. based on:

other: Structural components

Temp.:

25 °C

pH:

7

Remarks on result:

other: assume neutral pH

Details on results:

Water Sol from Kow (WSKOW v1.42) Results:
========================================

Water Sol: 0.6469 mg/L

SMILES : O=C(OC(CO)CO)C(O)CCCCCCCCCCCCCCCC
CHEM : Octadecanoic acid, hydroxy-, monoester with 1,2,3-propanetriol
MOL FOR: C21 H42 O5
MOL WT : 374.57
---------------------------------- WSKOW v1.42 Results ------------------------
Log Kow (estimated) : 5.08
Log Kow (experimental): not available from database
Log Kow used by Water solubility estimates: 5.08

Equation Used to Make Water Sol estimate:
Log S (mol/L) = 0.693-0.96 log Kow-0.0092(Tm-25)-0.00314 MW + Correction

Melting Pt (Tm) = 69.00 deg C (Use Tm = 25 for all liquids)

Correction(s): Value
-------------------- -----
No Applicable Correction Factors

Log Water Solubility (in moles/L) : -5.763
Water Solubility at 25 deg C (mg/L): 0.6469

The regression equations used by the WSKOWWIN program were trained with a dataset of 1450 compounds. WSKOWWIN estimates water solubility for any compound with one of two possible equations.  The equations are equations 19 and 20 from Meylan and Howard (1994a) or equations 11 and 12 from the journal article (Meylan et al., 1996).  The equations are:

     log S (mol/L)  =  0.796 - 0.854 log Kow - 0.00728 MW + ΣCorrections
    log S (mol/L)  =  0.693 - 0.96 log Kow - 0.0092(Tm-25) - 0.00314 MW + ΣCorrections

 (where MW is molecular weight, Tm is melting point (MP) in deg C [used only for solids]) ... Summation of Corrections (ΣCorrections) are applied as described in Appendix E.   When a measured MP is available, that equation is used; otherwise, the equation with just MW is used.
 
Accuracy statistics when a measured MP is used: r2 = 0.970. SD = 0.409. Avg Deviation = 0.313.

In this exercise, an experimental melting point is known and was entered into the input data.

Conclusions:

The water solubility of the substance is estimated to be < 1 mg/L, specifically 0.6469 mg/L, using the WSKOW (v.1.42) model of EPI Suite (v4.11).

Description of key information

Insoluble or poorly-soluble in water.

Key value for chemical safety assessment

Water solubility:

0.65 mg/L

at the temperature of:

20 °C

Additional information

The manufacturer of the registered substance has long considered this solid flaked material as "insoluble" in water. This is expected considering the fact it is the glycerol ester of a long-chain fatty acid., and is consistent with a modeled value (WSKOW, v 1.42) of 0.65 mg/L at 20 °C, although a different model using fragment constants estimates a higher solubility (4.95 mg/L). An experimental study (OECD 301B) was undertaken in which dissolution of the substance in deionised purified water was attempted, aided by techniques such as ultrasonication and high shear mixing. Both of these techniques failed to solubilise 50 mg of test material in a liter of water. The substance appears to meet the criteria for a "poorly water-soluble organic compound", according to the ISO (10634, 1995).

These observations and modeled water solubility estimates are in line with other substances of similar chemical structure. Water solubility values of other glycerides, as reported in the 2014 OECD SIDS for "Glycerides Category", range from 0.05 to 3020 mg/L at 20 °C. Two related triglyceride compounds, hydrogenated castor oil (CAS 61790 -39 -4) and castor oil (CAS 8001 -79 -4), which are metabolised to GMHS, are also insoluble in water (CIR, 2007). A metabolite of GMHS, 12 -hydroxystearic acid (CAS 106 -14 -9) is reported to have a water solubility less than 1 mg/L (ECHA registration dossier). These estimated and experimental values consistently support the conclusion that the registered substance is insoluble or poor soluble in water.