Trihexadecyl citrate

Partition coefficient

Administrative data

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 October 2017 to 4 May 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 123 (Partition Coefficient (1-Octanol / Water), Slow-Stirring Method)

Version / remarks:

11 July 2006

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

slow-stirring method

Partition coefficient type:

octanol-water

Test material

Test material information

Constituent 1

Reference substance name:

Trihexadecyl citrate

EC Number:

224-931-9

EC Name:

Trihexadecyl citrate

Cas Number:

4560-68-3

Molecular formula:

C55H106O6

IUPAC Name:

trihexadecyl citrate

Test material form:

liquid

Specific details on test material used for the study:

The test substance, Triisocetyl Citrate was allocated the Smithers Viscient code ESTS 262/17 for reference throughout the study.
Name: Triisocetyl Citrate
Physical state: Clear liquid
Arrival date: 4 September 2017
Re-test date: 4 September 2019
Storage conditions: Room temperature (15 to 30°C)

Results and discussion

Partition coefficient

Key result

Type:

log Pow

Partition coefficient:

7.27

Temp.:

24.9 °C

pH:

> 5.61 - < 9.27

Remarks on result:

other: Mean (weighted for 1/variance)

Details on results:

Analytical Procedure for Partition Coefficient Testing
Originally a method was developed using liquid chromatography (LC) with time-of-flight mass spectrometry (ToF-MS); however when the validation was attempted for this there were issues with low and changing sensitivity. It was thought that this was due to contamination of the LC-ToF-MS instrument due to its heavy use. Four validation batches were attempted using the LC-ToF-MS but reliable results could not be obtained so no data has been reported for this.

Because of these issues it was decided to modify the method for analysis using an alternative liquid chromatography (LC) with mass spectrometry (MS/MS) instrument. This gave good sensitivity and reproducibility so this was the methodology which was validated.

The method was assessed against the criteria detailed in the following sections: 

Specificity
Diluent and double-distilled water saturated with n-octanol and n-octanol saturated with double-distilled water controls were free of any components that interfered with the analysis of Triisocetyl Citrate. The method was therefore considered specific for Triisocetyl Citrate. Example chromatograms of diluent, n-octanol saturated with double-distilled water control and double-distilled water saturated with n-octanol control are shown in Figure 9, Figure 10 and Figure 11 (attached), respectively.

Sensitivity
The lowest calibration standard, 0.0005 µg/mL; this demonstrated sufficient sensitivity. The LOQ was 0.075M (63998 µg/mL mean fortification level) for n-octanol saturated with double-distilled water and 0.01 µg/mL for double-distilled water saturated with n-octanol. Example chromatograms of the lowest standard and LOQ samples are shown in Figure 12, Figure 15 and Figure 18 (attached), respectively.

Linearity
Response of the LC-MS/MS system to Triisocetyl Citrate was quadratic with a 1/x weighting, over the range 0.0005 to 0.05 μg/mL, with a correlation coefficient >0.99. The linearity of detector response was therefore established. Example chromatograms of the lowest and highest calibration standards are shown in Figure 12 and Figure 13 (attached) and a representative calibration plot is shown in Figure 14 (attached).

Accuracy (Recovery)
The accuracy of the spiked n-octanol saturated with double-distilled water sample was within 70-110% mean recovery for 0.075M, 0.1M and 0.125M recovery levels. The full results are shown in Table 3 (attached).

The accuracy of the spiked double-distilled water saturated with n-octanol samples was within 70 to 110% mean recovery for 0.01, 0.05 and 0.1 µg/mL recovery levels. The full results are shown in Table 4 (attached).

Example chromatograms of validation samples are shown in Figure 15 to Figure 20 (attached).

Precision (Repeatability)
The precision of the samples had a percent standard deviation (%RSD) of < 20% for all levels for both phases. The full results are shown in Table 3 and Table 4 (attached).

Example chromatograms of validation samples are shown in Figure 15 to Figure 20 (attached).



Partition Coefficient
The partition coefficient test was initiated on 27 April 2018 by stirring n-octanol and water at the test temperature with test substance added to the vessels on 30 April 2018, at 08:50, and sampling commencing on 1 May 18 and finishing on 4 May 2018. The test temperature was set at 25 ± 1.0°C. The actual temperature measured during the test ranged from 24.5°C to 26.3°C with a mean temperature of 24.9°C. The temperature deviated from the acceptable range on three occasions for a total period of 45 minutes, for 15 minutes on 2 May 18 up to 26.3°C, for 15 minutes on 3 May 18 up to 26.2°C and for 15 minutes on 4 May 18 up to 26.1°C. Each occasion coincided with a sampling timepoint, where the incubator temperature increased to compensate for the door of the incubator being opened.

The sampling times and pH measurements are shown in Table 9 (attached) and the partition coefficient results shown in Table 10 (attached) .

For the aqueous phase analysis, 8 mL of water was taken from the vessels and 2 mL THF added to the samples and the samples further diluted 0.2 mL to 1 mL with diluent. The control was treated in like manner. During the test, it was found that the concentration was lower than expected, so the further dilution step was not performed for the samples to be within the calibration range.

For the n-octanol phase analysis, 0.02 mL was taken from the vessels and diluted to 10 mL with THF. The samples were further diluted 0.1 mL to 10 mL with THF, then 0.1 mL to 10 mL with diluent. The control was treated in a likewise manner.

The calculated mass balance values were 87.00% for vessel 1, 100.53% for vessel 2 and 113.91% for vessel 3.

The samples were found to be within the validation range and a mean partition coefficient (Log Pow), weighted for 1/variance, of 7.27 was obtained with a weighted standard deviation of 0.0804.

Comparative chromatograms are shown in Figure 29 to Figure 36 (attached).

Applicant's summary and conclusion

Conclusions:

The octanol-water partition coefficient of the test substance was determined to be 7.27 Log Pow at 24.9 °C, under the conditions of the test.

Executive summary:

In this guideline (OECD 123) study, conducted with GLP certification, the octanol-water partition coefficient was found to be 7.27 at 24.9 °C.