2,2'-(naphthalene-1,4-diyl)bis(benzoxazole)

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January from 14 to 25, 2019

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Reason / purpose for cross-reference:

reference to other study

Remarks:

validated analytical method

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

adopted July 27, 1995

Deviations:

yes

Remarks:

the means obtained from two tests with different flows differ by more than 30 %;anyway, the deviation is not considered to affect the integrity and validity of the Study.

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

19 March 2014

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7840 (Water Solubility)

Version / remarks:

March 1998

GLP compliance:

yes (incl. QA statement)

Type of method:

column elution method

Water solubility:

0.002 mg/L

Conc. based on:

test mat.

Temp.:

20 °C

pH:

7.4 - 8.4

Details on results:

The mean concentration at 25 ml/hour flow rate resulted to be 0.00108 µg/ml and the mean concentration at 12.5 ml/hour flow rate resulted to be 0.00136 µg/ml.
Before the pH measurement, 2-point calibration of the pH meter was performed. The calibrated range was between 7.000 and 10.000, the measurement was performed at 20 ±1 °C. The measured pH values were between 7.4 and 8.4.

The means obtained from two tests with different flows differ by more than 30 %; this deviation from testing guideline is considered to be due to limitations of the analytical method at very low concentration. Anyway, the deviation is not considered to affect the integrity and validity of the Study.

CALIBRATION
Mean of the peak areas versus the concentration of the test item showed good linearity in the whole tested range of 0.0001 – 0.1 µg/ml. The calibration graph was calculated applying weighted linear regression. The weighting factor was 1/concentration.

Measured concentration of test item

Time Period	Mean concentration, µg/ml Column 1.	Mean concentration, µg/ml Column 2.
Measured concentration of test item at 25 ml/hour flow rate
70 hours	0.00137	0.00107
71 hours	0.00114	0.00086
72 hours	0.00114	0.00110
73 hours	0.00114	0.00104
74 hours	0.00103	0.000916
Mean	0.00117 µg/ml	0.000997 µg/ml
RSD	11 %	11 %
Mean all	0.00108 µg/ml
Measured concentration of test item at 12.5 ml/hour flow rate
120 hours	0.000170	0.000116
121 hours	0.000108	0.000088
122 hours	0.000103	0.000145
123 hours	0.000142	0.000147
124 hours	0.000185	0.000159
Mean	0.000142 µg/ml	0.000131 µg/ml
RSD	26 %	22 %
Mean all	0.000136 µg/ml

Conclusions:

Water solubility: 0.0015 mg/l at 20 °C and pH 7.4 -8.4

Executive summary:

The water solubility of the test item was determined using the column elution method, according to the OECD guideline 105.

A preliminary test for solubility was carried out as a range finding test for the decision whether the column elution method or the flask method needed to be used for the performance of the main test: a saturated solution of the test item in water was prepared by shaking a mixture of the test item and water at room temperature; after filtration the concentration of the saturated solution was determined to be less than 10 mg/l, therefore the column elution method was chosen for the main test.

Approximately 25 mg of the test item was dissolved in 25 ml tetrahydrofuran and this solution was added to 100 g of the support material. The solvent was completely evaporated. The dry, loaded support material was poured into the micro-columns. They were filled with water and the system was then equilibrated for two hours.

Then the columns were connected to the re-circulating pump. The columns were maintained at 20 ± 0.5 °C. Two different flow rates were applied: 25 ml/hour and 12.5 ml/hour with two replicate micro-columns.

During the calibration, mean of the peak areas versus the concentration of the test item showed good linearity in the whole tested range of 0.0001 – 0.1 µg/ml.

The mean concentration at 25 ml/hour flow rate resulted to be 0.00108 µg/ml and the mean concentration at 12.5 ml/hour flow rate resulted to be 0.00136 µg/ml; therefore the solubility resulted to be 0.0015 µg/ml at 20 °C; the measured pH values were between 7.4 and 8.4.

The means obtained from two tests with different flows differ by more than 30 %; this deviation from testing guideline is considered to be due to limitations of the analytical method at very low concentration. Anyway, the deviation is not considered to affect the integrity and validity of the Study.

Conclusion

Water solubility: 0.0015 mg/l at 20 °C and pH 7.4 -8.4

Description of key information

0.0015 mg/l at 20 °C and pH 7.4 -8.4

Key value for chemical safety assessment

Water solubility:

0.002 mg/L

at the temperature of:

20 °C

Additional information

OECD 105 - column elution method