tris(2-octyldodecyl) citrate

Water solubility

Administrative data

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 August 2017 to April 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

27 July 1995

Deviations:

no

Principles of method if other than guideline:

Method validation:

Analytical Procedure in Double-Distilled Water for Water Solubility Testing
The procedure, SMV (PC) 3201997-02V.sol, for determining the content of test substance in double-distilled water was developed in this study. The method used was liquid chromatography (LC) with time-of-flight mass spectrometry (TOF-MS). A summary of the analytical procedure is shown in Appendix 3 (attached).
The method was originally issued as SMV (PC) 3202997-01V.sol but this contained different LC TOF-MS conditions to those actually used and a narrower calibration range to the one actually used for the water solubility testing. Because of this the method was re-issued as the current version SMV (PC) 3201997-02V.sol.
The method was assessed against the criteria detailed in the following sections:
Specificity
The effect of the matrix containing the analyte was investigated. Blank solutions were prepared and run with the rest of the validation samples, to assess freedom from any interfering (co-chromatographic) peaks.
Sensitivity
The sensitivity (limit of quantification) of the method was assessed at a level considered acceptable for the analytical requirements. The limit of quantification (LOQ) was described as the lowest validation level where acceptable precision and accuracy data were obtained.
Linearity
The analytical calibration covered a range appropriate for the anticipated concentration of test substance in double-distilled water. The linearity of detector response for standard solutions over the concentration range (minimum of five different concentrations) was determined by least squares linear regression with a 1/x weighting. The acceptable correlation coefficient (r) was ≥ 0.99.

Accuracy and Precision (Repeatability)
For procedure SMV (PC) 3201997-02V.sol, the accuracy and precision of the analysis was determined by analysis of five replicates of prepared sample solutions. The sample solutions were prepared at the following concentrations 0.04, 0.1 and 0.5 µg/mL by spiking into double-distilled water from a solution of test substance in THF. The solutions were diluted with THF. The solutions were then further diluted with diluent, if required, to bring the concentration within the calibration range and then analysed using method SMV (PC) 3202072-02V.sol.
Acceptance criteria (SANCO/3029/99 rev. 4.)
Accuracy (recovery)
The mean recovery values should be within 70 to 110 %. (Ideally with the mean in the range 80% to 100%).

A suitable test for outliers may be applied to the accuracy data, for example the Grubbs or Dixons Tests.

Precision (repeatability)
The precision percent relative standard deviation (%RSD) should be ≤ 20%.

Analytical Procedure for Water Solubility Testing
The method validation was carried out twice. In the first batch the mean recovery and percent relative standard deviation (%RSD) values for the high validation level (0.5 µg/mL) failed with values of 114.48 and 21.13%, respectively. These samples were re-diluted and re-analysed and the mean recovery and %RSD were acceptable. Both sets of results have been reported.

The methods were assessed against the criteria detailed in the following sections:
Specificity
Diluting solvent was free of any components that interfered with the analysis of the test substance. There were small responses for the test substance in the diluent blanks and double-distilled water control; however these were all less than 30% of the response for the limit of quantification (0.04 µg/mL) (peak areas ranged from 4 to 22% of the 0.03 µg/mL calibration standard for the diluent blanks and 6% for the water control). Based on this the method was therefore considered specific for the test substance. Example chromatograms of diluting solvent, calibration standards, and validation samples are presented in Figure 2 to Figure 7 (attached).
Sensitivity
The limit of quantification (LOQ) was considered to be the lowest validation level which gave acceptable mean recovery and percent relative standard deviation (%RSD) values which in this case was at 0.04 µg/mL.
In addition the lowest calibration standard used was 0.005 µg/mL and this demonstrated sufficient sensitivity.
Linearity
Response of the LC-MS/TOF system to the test substance was linear with a 1/x weighting, over the range 0.005 to 0.2 μg/mL, with a correlation coefficient >0.99. The linearity of detector response was therefore established. A representative calibration plot is presented in Figure 11 (attached).
Accuracy (Recovery)
The accuracy of the spiked double–distilled water was within the acceptable range of 70 to 110 % mean recovery for the 0.04, 0.1 and 0.5 µg/mL validation levels.
The high validation level at 05 µg/mL originally failed with high mean recovery and %RSD values. The samples were re-diluted and re-analysed and were within the acceptance criteria. The individual results at the 0.5 µg/mL level were generally high (recoveries ranged from 93.79% to 123.44%); however as the mean recovery value was within the acceptance criteria and the maximum concentration found in the water solubility test was 0.08528 µg/mL this is not considered to be an issue.

The full results are shown in Table 1 (attached).

Precision (Repeatability)
The precision of the spiked double–distilled water had a percent standard deviation (%RSD) of < 20% for the 0.04, 0.1 and 0.5 µg/mL validation levels.

GLP compliance:

yes (incl. QA statement)

Other quality assurance:

ISO/IEC 17025 (General requirements for the competence of testing and calibration laboratories)

Type of method:

flask method

Test material

Test material information

Constituent 1

Reference substance name:

1,2,3-tris(2-octyldodecyl) 2-hydroxypropane-1,2,3-tricarboxylate

EC Number:

603-121-2

Cas Number:

126121-35-5

Molecular formula:

C66H128O7

IUPAC Name:

1,2,3-tris(2-octyldodecyl) 2-hydroxypropane-1,2,3-tricarboxylate

Test material form:

liquid

Details on test material:

Tris(octyldodecyl) citrate 99.87 %
Bis(octyldodecyl) citrate 0.13 %

Specific details on test material used for the study:

The test substance, 2,3-Propanetricarboxylic acid, 2-hydroxy-1,2,3-tris(2-octyldodecyl) ester was allocated the code ESTS 69/17 for reference throughout the study.
Name: 2,3-Propanetricarboxylic acid, 2-hydroxy-1,2,3-tris(2-octyldodecyl) ester (Citmol 320)
Physical state: Clear, faintly yellow liquid
Purity: 99.39%
Molecular weight: 1033.74 g/mol
Storage conditions: Room temperature (15 to 30°C)

Results and discussion

Water solubility

Key result

Water solubility:

< 0.043 µg/L

Conc. based on:

test mat.

Incubation duration:

ca. 457 h

Temp.:

20 °C

pH:

> 5.57 - < 6.83

Details on results:

The samples from vessel 1 showed concentrations both below the calibration line and the LOQ of 0.04 µg/mL for the duration of the testing, with no quantifiable amounts for the first six time points samples.

The first time point samples for vessel 2 were below the calibration line (lowest standard in run was 0.01 µg/mL), the calibration line was then extended down to 0.005 µg/mL, for all successive analysis, and subsequent samples were within the calibration. The first seven time point samples were below the LOQ (0.04 µg/mL) for vessel 2; however subsequent samples were above LOQ and the solubility in vessel 2 stabilised to give results with an acceptable % RSD.

The test temperature was 20 ± 0.5°C with deviations detailed in the Materials and Methods Section and Appendix 1 (attached) (min 19.7, max 20.7°C). The pH measurements are shown in Table 4 and the water solubility results shown in Table 5 (attached).

The samples for vessel 1 gave no quantifiable result for samples 1 to 6, then a mean water solubility value of 0.003 µg/mL with a % RSD of 22.2% for samples 8 to 13. The samples for vessel 2 gave a mean water solubility value of 0.046 µg/mL with a % RSD of 8.4%.

Due to the differences between the results from the two vessels and the fact that the first vessel gave a mean result below the LOQ it was decided that the water solubility would be reported as less than the mean of the LOQ, 0.04 µg/mL, and the mean result from vessel 2, 0.046 µg/mL, which gives a mean value of < 0.043 µg/mL.
Comparative chromatograms are shown in Figure 9 and Figure 10 (attached).

Any other information on results incl. tables

See figures and tables attached.

Applicant's summary and conclusion

Conclusions:

The water solubility of the test substance was found to be <0.043 µg/l at 20 °C ±0.5 °C, under the conditions of the test.

Executive summary:

In this guideline (OECD 105) study, conducted with GLP certification, the water solubility of the test substance was found to be <0.043 µg/l at 20 °C ±0.5 °C.