Docusate sodium

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

yes

Remarks:

The EC method A.6 requires a sequenced sampling after 1, 2 and 3 days of equilibration in order to check if saturation was achieved. Due to the long-term saturation period of 35 days sampling was done on day 35 only.

Qualifier:

according to guideline

Guideline:

other: Slow-stir method as referred in the ECHA document 'Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance' (May 2008)

Deviations:

no

Principles of method if other than guideline:

The test substance is a surfactant. The established methods for the determination of the water solubility as
described in EC A.6 and OECD 105 are not applicable to surfactants. Therefore a method variation of the equilibration
step based on the publication of D.J. Letinski et al. (Chemosphere 48 (2002), 257-265) was applied.

GLP compliance:

no

Type of method:

flask method

Water solubility:

8.17 g/L

Temp.:

20 °C

pH:

5

In the following table raw data and measurement results of the saturated solutions after 35 days of slow stearing are given.

Parameter		Solution I	Solution II	Solution III
Weight of the test substance [g]		1.903	2.064	1.965
Volume of double distilled water [mL]		40	40	40
pH of clear saturated solution		5.5	5.0	5.0
Concentration of saturated solution [g/L]	Measurement I	7.690	8.131	8.283
	Measurement II	7.757	8.094	8.190

From a statistical point of view (t-test, confidence level 95%) the results of solution I are outliers. Therefore they were discarded for further calculations. Results of solutions II and III were used for further calculations. The solubility of the test substance in water at 20 °C was obtained by calculating the mean value of solutions II and III. The mean value is 8.17 g/l. The most important contribution to the uncertainty of the result comes from the distribution of analytical measurements. The standard deviation of the results of solutions II and III was calculated to be 0.08 g/l, giving an expanded uncertainty of 0.16 g/l (coverage factor k=2).

An additional contribution to the uncertainty of the solubility arises from the fact that the test substance might be contaminated by sulfur containing compounds (see composition chap. 2.4). Unfortunately, there are to many unknown parameters related to this problem in order to discuss the contribution to the uncertainty on a theoretical basis. These parameters are for example the true content of each of these contaminations,

the solubility of the contaminations in the presence of the main component, the influence of the contaminations on the solubility of the main component etc.

Thus the final result for the water solubility of Docusate sodium at 20 °C is 8.17 ± 0.16 g/l.

Conclusions:

Interpretation of results (migrated information): soluble (1000-10000 mg/L)
The water solubility is 8.17 g/L.

Executive summary:

The water solubility of Docusate Sodium at 20 °C was investigated by the slow-stir method as referred in the ECHA document 'Guidance on information requirements and chemical safety assessment, Chapter R.7a: Endpoint specific guidance' (May 2008). Basic principles and requirements of the established method EC A.6 were followed. The concentration in the saturated solution was determined by XRF measurement to be 8.17 ± 0.16 g/l..

The results of this study are considered to be acceptable for the risk assessment.

Description of key information

8.17 g/L

Key value for chemical safety assessment

Water solubility:

8.17 g/L

at the temperature of:

20 °C

Additional information

For the determination of the water solubility of Docusate Sodium one Klimisch 1 key study is available (Redlich 2010). This study was performed using the internationally accepted slow stir method recommended for surface active substancesa and resulted in 8.17 +/- 0.16 g/L.

The experimentally determined water solubility of 8.17 g/L was considered as reliable and relevant for the further risk assessment.