Sodium dihydrogenorthophosphate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Testing was conducted between 29 September 2009 and 15 October 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Deviations:

no

GLP compliance:

yes

Remarks:

Date of inspection: 19 August 2008 Date of Signature: 04 March 2009

Type of method:

flask method

Remarks:

The determination was carried out using the flask method, Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.

Water solubility:

> 50.2 - < 52 other: % w/w

Temp.:

20 °C

pH:

>= 3.6 - <= 4

Details on results:

Please see section Remarks on results including tables and figures.

Preliminary test

The sample concentrations and observations recorded on completion of each 24 hour equilibration period are shown in the following tables:

Table5.3– Observations after Equilibration at 30°C

Sample Identity	Concentration (% w/w)	Observations
1	29.9	Clear colourless solution, free from any excess, un-dissolved test material.
2	40.6	Clear colourless solution, free from any excess, un-dissolved test material.
3	50.2	Clear colourless solution, free from any excess, un-dissolved test material.
4	60.0	Clear colourless solution containing a small quantity of excess, un‑dissolved test material.
5	70.0	Clear colourless solution containing a large quantity of excess, un‑dissolved test material.

 

Table5.4– Observations after Equilibration at 20°C

Sample Identity	Concentration (% w/w)	Observations
1	29.9	Clear colourless solution, free from any excess, un-dissolved test material.
2	40.6	Clear colourless solution, free from any excess, un-dissolved test material.
3	50.2	Clear colourless solution, free from any excess, un-dissolved test material.
4	60.0	Clear colourless solution containing a small quantity of excess, un‑dissolved test material.
5	70.0	Sample has almost completely solidified; contained very little solution.

Table5.5– Observations after Equilibration at 10°C

Sample Identity	Concentration (% w/w)	Observations
1	29.9	Clear colourless solution, free from any excess, un-dissolved test material.
2	40.6	Clear colourless solution, free from any excess, un-dissolved test material.
3	50.2	Clear colourless solution, free from any excess, un-dissolved test material.
4	60.0	Clear colourless solution containing a small quantity of excess, un-dissolved test material.
5	70.0	Sample has completely solidified; contained no visible solution.

The solution pH’s on completion of the preliminary test are shown in the following table:

Table5.6

Sample Identity	Concentration (% w/w)	Solution pH
1	29.9	3.9
2	40.6	3.7
3	50.2	3.6
4	60.0	3.7
5	70.0	[1]

Preliminary test result:      Solubility at 30.0°C: In the range 50.2 to 60.0% w/w
                                             Solubility at 20.0°C: In the range 50.2 to 60.0% w/w
                                               Solubility at 10.0°C: In the range 50.2 to 60.0% w/w                

Definitive test

The sample concentrations, observations recorded and solution pH on completion of the 24 hour equilibration period at their respective temperatures are shown in the following tables:

Table 5.7– Observations after Equilibration at 30°C

Sample Identity	Concentration (% w/w)	Observations
1	52.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.
2	54.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.
3	55.9	Clear colourless solution containing a quantity of excess, un-dissolved test material.
4	58.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.

Table5.8– Observations after Equilibration at 20°C

Sample Identity	Concentration (% w/w)	Observations
1	52.0	Clear colourless solution containing a quantity of excess, un‑dissolved test material.
2	54.0	Clear colourless solution containing a quantity of excess, un‑dissolved test material.
3	55.9	Clear colourless solution containing a quantity of excess, un‑dissolved test material.
4	58.0	Clear colourless solution containing a quantity of excess, un‑dissolved test material.

Table5.9– Observations after Equilibration at 10°C

Sample Identity	Concentration (% w/w)	Observations
1	52.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.
2	54.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.
3	55.9	Clear colourless solution containing a quantity of excess, un-dissolved test material.
4	58.0	Clear colourless solution containing a quantity of excess, un-dissolved test material.

 

The solution pH’s on completion of the definitive test are shown in the following table:

Table5.10

Sample Identity	Concentration (% w/w)	Solution pH
1	52.0	4.0
2	54.0	3.8
3	55.9	3.8
4	58.0	3.7

Definitive test result:          Solubility at 30.0°C: In the range 50.2 to 52.0% w/w
                                             Solubility at 20.0°C: In the range 50.2 to 52.0% w/w
                                               Solubility at 10.0°C: In the range 50.2 to 52.0% w/w

[1]Unable to record due to the physical state of the sample.

Conclusions:

Interpretation of results (migrated information): very soluble (> 10000 mg/L)
The water solubility of the test material has been determined. The results are shown in the following table:

Test Temperature Water Solubility Typical Solution pH
30.0 ± 0.5°C In the range 50.2 to 52.0% w/w 3.6 to 4.0
20.0 ± 0.5°C In the range 50.2 to 52.0% w/w 3.6 to 4.0
10.0 ± 0.5°C In the range 50.2 to 52.0% w/w 3.6 to 4.0
The temperature range 10 to 30°C had no significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material disodium hydrogenorthophosphate (sourced from Harlan Laboratories Ltd project number 2920/0004). From this data it could be concluded the solubility of the test material would decrease slightly as the pH increased over the pH range of 4 to 9. However, it must be noted that solubility would still remain high (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2) and such a decrease would only be observed if significant buffering capacity was present which prevented the formation of an acidic solution as formed on dissolution of the test material.

This study is conducted according to an appropriate guideline and under the conditions of GLP and therefore the study is considered to be acceptable and to adequately satisfy both the guideline requirement and the regulatory requirement as a key study for this endpoint.

Executive summary:

Method

The determination was carried out using a flask method based on Method A6 Water Solubility of CommissionRegulation (EC) No 440/2008 of 30 May 2008.

Conclusion

The water solubility of the test material has been determined. The results are shown in the following table:

Test Temperature	Water Solubility	Typical Solution pH
30.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0
20.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0
10.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0

The temperature range 10 to 30°C had no significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material disodium hydrogenorthophosphate (sourced from Harlan Laboratories Ltd project number 2920/0004). From this data it could be concluded the solubility of the test material would decrease slightly as the pH increased over the pH range of 4 to 9. However, it must be noted that solubility would still remain high (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2) and such a decrease would only be observed if significant buffering capacity was present which prevented the formation of an acidic solution as formed on dissolution of the test material.

Description of key information

The water solubility of sodium dihydrogenorthophosphate was determined according to EU Method A.6 (Water solubility) and under the conditions of GLP. 

Additional information

The water solubility of the test material has been determined. The results are shown in the following table:

Test Temperature	Water Solubility	Typical Solution pH
30.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0
20.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0
10.0±0.5°C	In the range 50.2 to 52.0% w/w	3.6 to 4.0

The temperature range 10 to 30°C had no significant influence on the observed solubility of the test material. An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 was performed from water solubility data for the related test material disodium hydrogenorthophosphate (sourced from Harlan Laboratories Ltd project number 2920/0004). From this data it could be concluded the solubility of the test material would decrease slightly as the pH increased over the pH range of 4 to 9. However, it must be noted that solubility would still remain high (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2) and such a decrease would only be observed if significant buffering capacity was present which prevented the formation of an acidic solution as formed on dissolution of the test material.