Trisodium orthophosphate

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 30 September 2009 and 13 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 (incl. QA statement)

Remarks:

Date of inspection: 2008-08-09 Date of Signature: 2009-03-04

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:

> 13 - < 14.1 other: % w/w

Temp.:

20 °C

pH:

12.6

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:

Observations after Equilibration at 30°C

Sample Identity	Concentration (% w/w)	Observations
1	5.3	Clear colourless solution, free from any excess, un-dissolved test material.
2	10.1	Clear colourless solution, free from any excess, un-dissolved test material.
3	15.0	Clear colourless solution, free from any excess, un-dissolved test material.
4	20.1	Clear colourless solution, containing a small quantity of excess, un-dissolved test material.
5	25.0	Clear colourless solution, containing a much excess, un-dissolved test material.

Observations after Equilibration at 20°C

Sample Identity	Concentration (% w/w)	Observations
1	5.3	Clear colourless solution, free from any excess, un-dissolved test material.
2	10.1	Clear colourless solution, free from any excess, un-dissolved test material.
3	15.0	Clear colourless solution, containing a small quantity of excess, un-dissolved test material.
4	20.1	Clear colourless solution, containing a large quantity of excess, un-dissolved test material.
5	25.0	A small volume of clear colourless solution present, the sample consisting of predominantly excess, un-dissolved test material.

Observations after Equilibration at 10°C

Sample Identity	Concentration (% w/w)	Observations
1	5.3	Clear colourless solution, free from any excess, un-dissolved test material.
2	10.1	Clear colourless solution containing a small quantity of crystallised excess, un-dissolved test material.
3	15.0	Clear colourless solution, containing a large quantity of excess, un-dissolved test material.
4	20.1	Clear colourless solution, containing a large quantity of excess, un-dissolved test material.
5	25.0	Clear colourless solution, containing a large quantity of excess, un-dissolved test material.

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

Sample Identity	Concentration (% w/w)	Solution pH
1	5.3	12.5
2	10.1	12.5
3	15.0	12.3
4	20.1	12.0
5	25.0	11.8

Preliminary test result:     Solubility at 30.0°C: In the range 15.0 to 20.1% w/w
                                     Solubility at 20.0°C: In the range 10.1 to 15.0% w/w
                                       Solubility at 10.0°C: In the range 5.32 to 10.1% 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:

Observations for 30°C Samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
1	16.1	Clear colourless solution containing a quantity  of crystalline, excess, un-dissolved test material.	12.4
2	17.0	Clear colourless solution containing a quantity  of crystalline, excess, un-dissolved test material.	12.4
3	18.0	Clear colourless solution containing a quantity  of crystalline, excess, un-dissolved test material.	12.4
4	19.0	Clear colourless solution containing a quantity of  crystalline, excess, un‑dissolved test material.	12.4

 

Observations for 20°C Samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
1	11.1	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
2	12.2	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
3	13.0	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
4	14.1	Clear colourless solution containing a quantity of crystalline, excess, un‑dissolved test material.	12.5

Observations for 10°C Samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
1	6.0	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
2	7.0	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
3	8.0	Clear colourless solution, free from any excess, un-dissolved test material.	12.6
4	9.0	Clear colourless solution, free from any excess, un-dissolved test material.	12.6

Definitive test result:        Solubility at 30.0°C: In the range 15.0 to 16.1% w/w
                                     Solubility at 20.0°C: In the range 13.0 to 14.1% w/w
                                       Solubility at 10.0°C: In the range 9.0 to 10.1% w/w

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 15.0 to 16.1% w/w 12.4
20.0 ± 0.5°C In the range 13.0 to 14.1% w/w 12.6
10.0 ± 0.5°C In the range 9.0 to 10.1% w/w 12.6
The temperature range 10 to 30°C had a 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 materials disodium hydrogenorthophosphate and sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0004 and 2920/0001 respectively). From this data it be concluded that the solubility of the test material (trisodium orthophosphate) would increase significantly as the pH decreased over the pH range of 9 to 4 (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2 and in the range 50.2 to 52.0% w/w at 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of a strongly alkali 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:

INTRODUCTION

The water solubility of the test material have been determined.

Methods employed complied with those specified in Commission Regulation (EC) No 440/2008 of 30 May 2008, Part A: Methods for the determination of physico-chemical properties.

Testing was conducted between 30 September 2009 and 13 October 2009.

Method

The determination was carried out using a flask method based on Method A6 Water Solubility ofCommissionRegulation (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:

Table 5.13

Test Temperature	Water Solubility	Typical Solution pH
30.0±0.5°C	In the range 15.0 to 16.1% w/w	12.4
20.0±0.5°C	In the range 13.0 to 14.1% w/w	12.6
10.0±0.5°C	In the range 9.0 to 10.1% w/w	12.6

The temperature range 10 to 30°C had a 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 materials disodium hydrogenorthophosphate and sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0004 and 2920/0001 respectively). From this data it be concluded that the solubility of the test material (trisodium orthophosphate) would increase significantly as the pH decreased over the pH range of 9 to 4 (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2 and in the range 50.2 to 52.0% w/w at 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of a strongly alkali solution as formed on dissolution of the test material.

Description of key information

The water solubility of trisodium orthophosphate 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 (w/w)	Typical solution pH
30.0±0.5°C	In the range 15.0 to 16.1%	12.4
20.0±0.5°C	In the range 13.0 to 14.1%	12.6
10.0±0.5°C	In the range 9.0 to 10.1%	12.6

The temperature range 10 to 30°C had a 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 materials disodium hydrogenorthophosphate and sodium dihydrogenorthophosphate (sourced from Harlan Laboratories Ltd project numbers 2920/0004 and 2920/0001 respectively). From this data it be concluded that the solubility of the test material (trisodium orthophosphate) would increase significantly as the pH decreased over the pH range of 9 to 4 (in the range 23.8 to 25.1% w/w at 20°C, pH 9.2 and in the range 50.2 to 52.0% w/w at 20°C, pH 3.6 to 4.0). However, it must be noted that such an increase would only be observed if significant buffering capacity was present which prevented the formation of a strongly alkali solution as formed on dissolution of the test material.