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EC number: 943-932-1 | CAS number: 26834-28-6
Water solubility
Administrative data
Link to relevant study record(s)
Description of key information
In a study using the flask method (Laus 2014), the water solubility could not be conclusively assessed, due to the inability of the lab to achieve a clear solution. After several-fold dilution, the clear solution contained no detectable amount of the test substance. A QSAR according to Waternt v1.01 (EPIWIN) showed a water solubility of 4.8E-04 µg/L. This low value indicates that the water solubility of NaDNNSA is similar to the water solubility of the structural analogues DNNSA and BaDNNSA.
Key value for chemical safety assessment
- Water solubility:
- 0.229 mg/L
- at the temperature of:
- 20 °C
Additional information
In the water solubility tests that are available for all compounds, difficulties to assess an actual value were seen. This is not surprising in view of the complex structure of the substances. The ECHA guidance on Information Requirements[1]indicates for UVCB substances: “solubility of a single substance in water is not applicable to substances which are multi-component, such as multi-constituent or UVCB substances, i.e. complex substances. The usually accepted meaning of ‘solubility’ in such cases is ‘the composition of the aqueous solution formed at equilibrium under a defined set of conditions’. Temperature and the amount of substance added per unit volume of water (i.e. the ‘loading’) are the main factors to consider. It may not always be possible to establish that equilibrium of all components has been achieved; in these cases, time and type of agitation of the test vessels must also be described”. Different components of the UVCB may exhibit different water solubility, so that in practice water solubility is not a single point, but likely to a range. It is noted that for complex substances water solubility may also be dependent on the loading rate. In addition, the analytical method (in all available studies based on a single peak in the chromatogram) may influence the assessed value strongly.
The methods to assess the water solubility of the source and target substances included both column elution and slow stirring approaches. The column elution test with NaDNNSA showed that the water solubility could not be conclusively assessed, as it was not possible to achieve a clear solution. Similar problems were found in the study on LiDNNSA.
In view of the uncertainties of the assessment of the water solubility on NaDNNSA described above, QSARs were run using the Epiwin model for NaDNNSA, although the Epiwin model in principle is not suitable for salts. The structures of NaDNNSA as shown in table 1 can be modelled but do not reflect the actual substance accurately, as this substance is an ionizable salt. Therefore the most reliable estimation for water solubility will be based on the test with the acid, which shows a water solubility of 0.229 mg/L. This value is considered to represent a worst case estimate for use in any risk assessment of NaDNNSA.
[1]Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance, Aug 2014
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