Reaction products of Dihydro-3-(tetrapropenyl)furan-2,5 dione with propane-1,2,diol

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 January 2016 to 07 December 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Key result

Water solubility:

55.09 mg/L

Conc. based on:

other: Free acid

Incubation duration:

24 h

Temp.:

20 °C

pH:

7

Key result

Water solubility:

13.43 mg/L

Conc. based on:

other: Monoester

Incubation duration:

24 h

Temp.:

20 °C

pH:

7

Key result

Water solubility:

< 0.2 mg/L

Conc. based on:

other: Diester

Incubation duration:

24 h

Temp.:

20 °C

pH:

7

Key result

Water solubility:

1.301 mg/L

Conc. based on:

other: Free acid

Remarks:

WATERNT method

Temp.:

25 °C

Remarks on result:

other: (WSKOW method: 2.706 mg/L)

Key result

Water solubility:

6.392 mg/L

Conc. based on:

other: Monoester

Remarks:

WATERNT method

Temp.:

25 °C

Remarks on result:

other: (WSKOW method: 2.136 mg/L)

Key result

Water solubility:

0 mg/L

Conc. based on:

other: Diester

Remarks:

WATERNT method

Temp.:

25 °C

Remarks on result:

other: WSKOW method: 0.0000001598 mg/L

Details on results:

Water Solubility
The mean water solubility results were as follows:
- The acid: 55.09 µg/mL.
- Monoester: 13.43 µg/mL.
- Diester: < 0.2 µg/mL.
- The analysis of the diester gave very variable results and poor calibration lines, because of this the results vary from < 0.02195 µg/mL (LOQ) to 0.2009 µg/mL. Due to these unreliable results, the value reported has been set to the next highest round number of < 0.2 µg/mL.
 
Stability samples
The stability samples run along with the water solubility samples confirmed stability of the samples with mean values as follows:
Mean % recovery for the acid:
- At start of water solubility testing: 134.98* and 147.85*
- After end of water solubility testing: 91.51 and 108.43
Mean % recovery Monoester:
- At start of water solubility testing: 88.04 and 86.95
- After end of water solubility testing: 89.85 and 90.33
Mean % recovery for Diester:
- At start of water solubility testing: 95.76 and 92.35
- After end of water solubility testing: 91.49 and 105.72
*The calibration line for the acid fell outside the acceptance criteria for correlation coefficient of > 0.99 (actual value was 0.97387) so these values are unreliable.
 
Calculated Values
-Calculated values for the water solubility were determined for each of the specified constituents of the test material stated in information provided by the Sponsor.
-The EPI ver 4.1 software used two different methods for calculating the adsorption coefficient, the WSKOW and WATERNT methods. Since experimental values for melting point and Kow were not used in the calculations, the values predicted by the WATERNT method are considered more reliable. The calculated values for the water solubility from these two methods were as follows:
 
- WSKOW calculated values:
Acid: Slightly soluble, predicted water solubility (at 25 °C) 2.706 mg/L.
Monoester: Slightly soluble, predicted water solubility (at 25 °C) 2.136 mg/L.
Diester: Negligible solubility, predicted water solubility (at 25 °C) 0.0000001598 mg/L.
 
- WATERNT calculated values:
Acid: Slightly soluble, predicted water solubility (at 25 °C) 1.3008 mg/L.
Monoester: Slightly soluble, predicted water solubility (at 25 °C) 6.3918 mg/L.
Diester: Negligible solubility, predicted water solubility (at 25 °C) 0.00000060886 mg/L.

Analytical Procedure

- Four validation batches were analysed as follows:

pH7 Val 1: Method validation for pH 7 buffer.

pH4 Val 1:Method validation for pH 4 buffer.

pH9 Val 1: Method validation for pH 9.

pH4 Val 2: Repeat of method validation for pH 4 buffer using freshly prepared samples.

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

Specificity:

Diluting solvent and blank control solutions were free of any components that interfered with the analysis of the test material. The method was therefore considered specific for the test material. All diluent or blank solution peaks had responses that were ≤ 30 % of the responses for the samples at the limit of quantification (LOQ).

Sensitivity:

The lowest calibration standard was 0.001 µg/mL (0.000371 µg/mL as the acid, 0.000190 µg/mL as the monoester and 0.000439 µg/mL as the diester which demonstrated sufficient sensitivity. The limit of quantification (LOQ) was defined as the lowest validation level that gave acceptable mean recoveries and percent relative standard deviation (%RSD).

pH	LOQ for the acid (µg/mL)	LOQ for the monoester (µg/mL)	LOQ for the diester (µg/mL)
4	0.01855	0.0095	0.02195
7	0.01855	0.0095	0.02195
9	0.01855	0.0095	2.195

Linearity:

Response of the LC-MS/MS TOF system to the test material with a 1/X weighting, over the range 0.001 to 0.1 μg/mL, (0.000371 to 0.0371 µg/mL as the acid, 0.000190 to 0.0190 µg/mL as the monoester and 0.000439 to 0.0439 µg/mL as the diester with correlation coefficients of > 0.99. The linearity of detector response was therefore established.

Accuracy (Recovery):

The accuracy mean recovery values varied between batches with no one batch showing acceptable recoveries at all validation levels for all three constituents.

pH	Validation batch	Constituent	Acceptable mean recoveries
			Low level	Mid-level	High level
4	1	Acid	No	Yes	No
		Monoester	Yes	Yes	Yes
		Diester	Yes	Yes	Yes
	2	Acid	Yes	Yes	Yes
		Monoester	Yes	Yes	Yes
		Dieste	Yes	Yes	Yes
7	1	Acid	Yes	Yes	Yes
		Monoester	Yes	Yes	Yes
		Diester	Yes	Yes	Yes
9	1	Acid	No	Yes	Yes
		Monoester	Yes	Yes	Yes
		Diester	No	Yes	Yes

The second pH 4 batch was a repeat validation, due to failure of the validation for the acid in the first batch. The pH 9 batch was not repeated as it was decided, in consultation with the Sponsor, that the water solubility test would only be carried out at pH 7 after the repeat validation at pH 4 had been done. The first validation batch at pH 7 was considered acceptable as it only failed at the high level for the acid.

Precision (Repeatability):

The precision %RSD values varied between batches with no one batch showing acceptable recoveries at all validation levels for all three constituents.

The summary of the acceptability of the precision %RSD results is as follows:

 

pH	Validation batch	Constituent	Acceptable %RSD
			Low level	Mid-level	High level
4	1	Acid	No	Yes	Yes
		Monoester	Yes	Yes	Yes
		Diester	Yes	Yes	Yes
	2	Acid	Yes	No	Yes
		Monoester	Yes	Yes	Yes
		Diester	Yes	No	Yes
7	1	Acid	Yes	Yes	Yes
		Monoester	Yes	Yes	Yes
		Diester	Yes	Yes	Yes
9	1	Acid	Yes	Yes	Yes
		Monoester	Yes	Yes	Yes
		Diester	No	Yes	Yes

Due to the poor validation results for the acid and the diester at all three pH levels and the fact that results for all three constituents were required for the water solubility testing it was decided, in consultation with the Sponsor, that the water solubility test would only be carried out at one pH. As the validation at pH 7 had the most consistent validation results it was decided that this would be the test pH used.

Stability samples

Stability sample	Analysis time	Mean % recovery for the acid	Mean % recovery monoester	Mean % recovery diester
1	At start of water solubility testing	135.09*	88.04	95.84
2	At start of water solubility testing	147.97*	86.95	92.43
3	After end of water solubility testing	91.54	89.94	91.52
4	After end of water solubility testing	108.46	90.42	105.76

*The calibration line for the acid fell outside the acceptance criteria for correlation coefficient of > 0.99 (actual value was 0.97387) so these values are unreliable.

Discussion of Differences between Measured and Calculated Water Solubility Values

- The measured water solubility results of 55.09 µg/mL for the acid and 13.43 µg/mL for the monoester are much higher than the EPI Ver. 4.1 calculated values of 2.706 mg/L (WSKOW) and 1.3008 mg/L (WATERNT) for the acid and 2.136 mg/L (WSKOW) and 6.3918 mg/L (WATERNT) for the monoester. This difference in values is probably down to the fact that the EPI Ver. 4.1 values are estimates based on several assumptions.

For the WSKOW estimation method an estimated value of the log Pow is used. For the acid an estimated log Pow of 4.85 was used and for the monoester an estimated log Pow of 5.17 was used. These values of log Pow are much larger than the actual measured log Pow values which ranged from 1.15 to 2.36. Unfortunately it was not possible to identify which of the measured log Pow values applied to which of the three test material constituents so the actual log Pow values could not be accurately used in the EPI Ver 4.1 calculations. However lower log Pow values will give larger estimated water solubility values in the WSKOW calculation. It should also be noted that if a melting point is entered into the EPI Ver 4.1 software this will also be used in the WSKOW calculation; however this could not be done in this case as a definitive melting point could not be measured.

The WATERNT estimation method is a fragment-based method and like all fragment-based methods, the accuracy of its estimates is influenced by the relative number of fragments covered by the model. Generally the more fragments included in the model domain, the more accurate the estimate will be. However as the calculation is based on the combined estimated water solubility values of each fragment it is not going to fully represent the behaviour of the test substance.

As there were no obvious issues with the water solubility testing, such as formation of emulsions, that would indicate any issues with the test and as the results for the different water solubility samples agree well it is considered that the results from this testing are more accurate than the EPI Ver 4.1 calculated values.

Conclusions:

Under the conditions of this study the water solubility of the components of the test material were: Free acid: 55.09 µg/mL, monoester: 13.43 µg/mL and diester: < 0.2 µg/mL.
The calculated values (at 25 °C) were: Free acid: 2.706 mg/L (WSKOW method) and 1.3008 mg/L (WATERNT method), monoester: 2.136 mg/L (WSKOW method) and 6.3918 mg/L (WATERNT method) and diester: 0.0000001598 mg/L (WSKOW method) and 0.00000060886 mg/L (WATERNT method).

Executive summary:

The water solubility of the test material was investigated in accordance with the standardised guideline OECD 105, under GLP conditions.

The analytical methodology used was high performance liquid chromatography (HPLC) with time of flight mass spectrometry (TOF). Based on a preliminary estimation of water solubility, it was determined that the most appropriate method for the determination of water solubility was the shake flask method detailed in OECD guideline 105. The water solubility test was carried out in aqueous pH 7 buffer only.

Under the conditions of this study the water solubility of the components of the test material were free acid: 55.09 µg/mL, monoester: 13.43 µg/mL and diester: < 0.2 µg/mL.

The calculated values (at 25 °C) were: free acid: 2.706 mg/L (WSKOW method) and 1.3008 mg/L (WATERNT method), monoester: 2.136 mg/L (WSKOW method) and 6.3918 mg/L (WATERNT method) and diester: 0.0000001598 mg/L (WSKOW method) and 0.00000060886 mg/L (WATERNT method).

Description of key information

Under the conditions of this study the water solubility of the components of the test material were free acid: 55.09 µg/mL, monoester: 13.43 µg/mL and diester: < 0.2 µg/mL.

 

For the chemical safety assessment, a weighted average water solubility of 23.08 mg/L (at 20°C) was derived, based on the constituents’ experimentally derived water solubilities and their proportion (%) in the substance (see table below).

Constituent	Percentage in substance	Water solubility [µg/mL]	Water solubility component [µg/mL]
2-(tetrapropenyl)succinic acid	37.1	55.09	20.44
Monoester of 2-(tetrapropenyl)-succinic acid with propane-1,2-diol	19	13.43	2.55
Diester of 2-(tetrapropenyl)succinic acid with propane-1,2-diol	43.9	0.2	0.09
Weighted average water solubility component			23.08

Key value for chemical safety assessment

Water solubility:

23.08 mg/L

at the temperature of:

20 °C

Additional information

The water solubility of the test material was investigated in accordance with the standardised guideline OECD 105, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

The analytical methodology used was high performance liquid chromatography (HPLC) with time of flight mass spectrometry (TOF). Based on a preliminary estimation of water solubility, it was determined that the most appropriate method for the determination of water solubility was the shake flask method detailed in OECD guideline 105. The water solubility test was carried out in aqueous pH 7 buffer only.

Under the conditions of this study the water solubility of the components of the test material were free acid: 55.09 µg/mL, monoester: 13.43 µg/mL and diester: < 0.2 µg/mL.