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Physical & Chemical properties

Water solubility

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Description of key information

The water solubility of diisotridecyl adipate was assessed in an OECD 105 (Column Elution) study, resulting in 0.743 µg/L (± 0.088 µg/L) and 0.644 µg/L (± 0.047 µg/L) at flow rates of 0.50 mL/min and 0.25 mL/min, respectively. Results were found to meet the required quality criteria with a relative standard deviation less than 30 % within one sample batch and between sample batches at different flow rates and therefore the water solubility was determined to be 0.7 µg/L in deionized water.

Key value for chemical safety assessment

Water solubility:
0.7 µg/L
at the temperature of:
20 °C

Additional information

The water solubility of diisotridecyl adipate (DITA) was assessed in a study performed according to OECD guideline 105 (Column Elution) and GLP (Kotthoff, 2016). Bi-distillated water was used as test medium. Water solubilities are determined to be 0.743 μg/L (± 0.088 μg/L) and 0.644 μg/L (± 0.047 µg/L) at flow rates of 0.50 mL/min and 0.25 mL/min, respectively. Thus the water solubility is considered to be 0.7 µg/L in deionized water.

This finding is in line with values reported in the literature and measured for the structurally similar read-across substances use for the hazard assessment of DITA in this dossier. In the literature a water solubility of 0,001 mg DITA /L is described. This value is supported by EPIWIN calculations resulting in a value of 0.000000511 mg/L which can be interpreted as 0.1 mg/L and hence insolubility of the substance. A further measured value of 1.12 mg/L has been determined using the flask method (Harlan, 2010). In the ECHA guidance (R7.A) this method is only recommended for substances with higher water solubility (> 10 mg/L). Therefore this method is not considered to be appropriate for assessing the water solubility of DITA. Two other existing experimental results (Oxea, 2010 and Sasol, 2010) are considered limit tests up to the detection limits of the used analytical method.

Based on the poor solubility of DITA in water and the complex nature of this test compound, it is difficult to establish an appropriate experimental test setup for the determination of the exact water solubility of the substance. In parallel to the key study (OECD 105, Kotthoff, 2016) further water solubility experiments were conducted using other methods. For instance, tests according to a slow-stir protocol were performed and resulted in concentrations of 1.966 and 0.711 µg/L, respectively (2 replicates). However, since the key study fulfills the criteria as described in the respective OECD guideline (105) for insoluble/poorly soluble test substances, this value is selected as key information.

In addition to the determination of water solubility in deionized water, as laid out in the guideline, side experiments were set up to assess the solubility of diisotridecyl adipate in ecotoxicological test media (purified test water and ISO standard medium). The results indicate a high variability and differences in regard to the test medium and also among the individual replicates (a complete listing of results of the various side experiments can be found in the Water Solubility key study endpoint record in the IUCLID file). These observations could indicate the presence of undissolved test material and an overestimation of the exposure concentration.

Further water solubility tests in pure water and test media are currently ongoing using the passive dosing approach. The aim is to establish a test system which provides consistent and reproducible results in water and media to improve the accuracy and reliability of both the water solubility value and the exposure concentrations in ecotoxicological tests.