4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]diphthalic anhydride

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

September 2021 to December 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

GLP compliance:

yes (incl. QA statement)

Type of method:

column elution method

Specific details on test material used for the study:

Batch number: CT20201015
Re-test date: 10th September 2022
Storage conditions: store in a cool dry place

During the water solubility study, the anhydride is expected to ring-open to form the corresponding di-acid. Therefore, the water solubility will be that of the di-acid rather than the anhydride.

Key result

Water solubility:

< 0.062 mg/L

Conc. based on:

test mat.

Incubation duration:

24 h

Temp.:

20 °C

Remarks on result:

other: pH not measured

Details on results:

Preliminary Test

Test item 6FDA (0.1 g) was placed into a 10 mL measuring cylinder and topped up incrementally with water, whilst shaking, until the 10 mL mark was reached to make a 10000 mg/L solution. Dissolution was not observed.

Test item 6FDA (0.1 g) was placed into a 100 mL measuring cylinder and topped up incrementally with water, whilst shaking, until the 100 mL mark was reached to make a 1000 mg/L solution. Dissolution was not observed.

Test item 6FDA (0.98 mg) was placed into a 1 L flask containing 1 L of HPLC grade water. The flask was placed in a sonicator for 10 minutes, after which particles could still be seen in the bottle. The bottle was placed on a shaker at 20 oC and allowed to shake for 66 hours. Upon inspection the test item appeared undissolved.

Limit of Detection Test

To confirm the preliminary findings, a HPLC method was developed and the LOD was found to be 0.062 mg/L.

The 1000 mg/L aqueous suspension prepared for the preliminary estimation was analysed and found to have a concentration of approximately 200 mg/L. This was a contradiction to the less than 10 mg/L result for the preliminary estimation.

Further Analysis

Two preparations of 1 mg/L and 1 g/L concentrations were prepared and found to have 360 mg/L and 203000 mg/L respectively. It is believed that the solutions may have picked up some sodium or potassium ions from the glass vessels whilst standing.

To confirm this hypothesis the test item (20 mg) was added to 0.1M sodium hydroxide (20 mL). After sonication for approx 5 minutes followed by gentle warming the test item was fully dissolved. The presence of NaOH appeared to significantly increase the solubility of the test item. It is suspected that after the anhydride functional groups have been hydrolysed to the carboxylic acid groups, the free acid form of the molecule is less soluble than the various salt forms. Testing was therefore repeated using plastic vessels.

Preliminary Test - Plastic vessels

Preliminary estimation was repeated using a plastic vessel; 0.92 mg of test item was mixed with 1000 mL of water in a plastic vessel, placed on a shaker at 20 oC and left for 24 hours. A duplicate plastic vessel was filled with water and put on the shaker at the same time as a control. After shaking an aliquot was taken and filtered through a syringe filter into a HPLC vial. Water was taken from the duplicate vessel and used as a blank. The filtered sample and the blank were passed through the HPLC system.

The preliminary water solubility was found to be below the limit of detection (<0.062 mg/L)

Based on test guidelines when solubility is below 10 mg/L, the column elution method should be used to determine water solubility. However, as it was observed that glassware impacts results and the column elution method employs the use of glass beads, this method is unsuitable for determination of water solubility of the test item.

Conclusions:

The water solubility of the test item 6FDA was determined to be below the limit of detection (<0.062 mg/L)

Executive summary:

The water solubility of the test substance 6FDA was determined according to the OECD guideline 105 using a preliminary estimation and analysed using HPLC analysis.  The test substance is an anhydride that ring-opens in the presence of water to form the diacid.  It was found that the substance was incompatible with glassware as sodium and potassium ions form a salt with the di-acid which drastically increases the water solubility.  Therefore plastic vessels were used.  As such, a column elution method could not be used as the column requires the use of glassbeads.  Therefore, the preliminary estimation has been used to determine the water solubility.

 

The water solubility of 6FDA was determined to be below the limit of detection (<0.062 mg/L).

Description of key information

The water solubility of the test substance 6FDA was determined according to the OECD guideline 105 using a preliminary estimation and analysed using HPLC analysis.  The test substance is an anhydride that ring-opens in the presence of water to form the diacid.  It was found that the substance was incompatible with glassware as sodium and potassium ions form a salt with the di-acid which drastically increases the water solubility.  Therefore plastic vessels were used.  As such, a column elution method could not be used as the column requires the use of glassbeads.  Therefore, the preliminary estimation has been used to determine the water solubility.

 

The water solubility of 6FDA was determined to be below the limit of detection (<0.062 mg/L).