Tripotassium 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 02 October 2009 and 05 November 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:

yes

Remarks:

Due to the high solubility of the test material (see details below).

Principles of method if other than guideline:

Due to the high solubility of the test material, it was not possible to prepare samples at five times the estimated saturation concentration as required by EC Method A6 for subsequent analysis. In addition, due to the limited linear range of the available ion chromatography analytical method, it was concluded that the dilution factor necessary to obtain sample solutions within a concentration range suitable for analysis would result in possible experimental variances greater than the accuracy achieved by the visual assessment procedure applied. The saturation period and equilibration period of 72 hours and 24 hours respectively were as specified by EC Method A6 to retain as many of the guideline parameters as possible in the amended procedure.

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: 2008-08-19 Date of Signature: 2009-03-04

Type of method:

flask method

Remarks:

EXAMPLE: 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:

>= 62.4 - <= 65 other: % w/w

Temp.:

20 °C

pH:

> 14

Details on results:

Please see section Remarks on results including tables and figures.

Results

Preliminary test

The sample concentrations, observations and solution pH are shown in the following table:

Table 8

Sample Identity	Concentration (% w/w)	Observations	Solution pH
1	10.5	Test material fully dissolved.	12.8
2	21.2	Test material fully dissolved.	13.0
3	31.5	Test material fully dissolved.	13.3
4	41.7	Test material fully dissolved.	13.4
5	50.1	Test material fully dissolved.	13.8
6	59.8	Clear colourless, slightly viscous solution with no excess undissolved test material.	>14
7	70.7	Mixture consisting of a clear colourless liquid with excess undissolved test material.	>14
8	80.1	Wet white solid.	*
9	90.3	Slightly damp white solid.	*

Preliminary result:    20°C: In the range 59.8 % w/w to 70.7 % w/w                  

* unable to record due to the physical state of the sample

Definitive test

The sample concentrations, observations and solution pH are shown in the following tables:

Table 9. Observations for 30°C samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
18	60.6	Clear colourless liquid with no evidence of undissolved test material.	>14
19	62.4	Clear colourless liquid with no evidence of undissolved test material.	>14
20	65.0	Clear colourless liquid with no evidence of undissolved test material.	>14
21	67.5	Contains excess undissolved test material.	*
22	70.1	Contains excess undissolved test material.	*

* unable to record due to the physical state of the sample

Table 10. Observations for 20°C samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
10	62.4	Clear colourless liquid with no evidence of excess undissolved test material.	>14
11	65.0	Contains excess undissolved test material.	*
12	67.5	Contains excess undissolved test material.	*
23	66.9	Contains excess undissolved test material.	*
24	66.5	Contains excess undissolved test material.	*

* unable to record due to the physical state of the sample

Table 11. Observations for 10°C samples

Sample Identity	Concentration (% w/w)	Observations	Solution pH
13	59.6	Clear colourless liquid with no evidence of excess undissolved test material.	>14
14	62.7	Clear colourless liquid with no evidence of excess undissolved test material.	>14
15	65.6	Contains excess undissolved test material.	*
16	67.1	Contains excess undissolved test material.	*
17	70.4	Contains excess undissolved test material.	*

Overall results:          30°C: In the range 65.0 % w/w to 67.5 % w/w
                                  20°C: In the range 62.4 % w/w to 65.0 % w/w
                                  10°C: In the range 62.7 % w/w to 65.6 % w/w

* unable to record due to the physical state of the sample

Additional test

The sample concentrations, observations and solution pH are shown in the following tables:

Table 12.

Sample Identity	Concentration (% w/w)	Observations	Solution pH
25	50.0	Test material fully dissolved.	13.9
26	50.9	Test material fully dissolved.	>14

Overall results:          In the range 50.0 % w/w to 66.5 % w/w, using the pH 4 buffer solution; in the range 50.9 % w/w to 66.9 % w/w, using the pH 9 buffer solution

Conclusions:

Interpretation of results: very soluble (> 10000 mg/L)

The water solubility of the test material has been determined at 10, 20 and 30°C. Tripotassium orthophosphate was found to be very soluble (see results tables). The solution pH was determined to be >14.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 by visual assessment using a flask method, based on Method A6 Water Solubility of Commission Regulation (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 13

Test temperature	Water solubility	Typical solution pH
30.0±0.5°C	In the range 65.0 % w/w to 67.5 % w/w	>14
20.0±0.5°C	In the range 62.4 % w/w to 65.0 % w/w	>14
10.0±0.5°C	In the range 62.7 % w/w to 65.6 % w/w	>14

Overall, the effect of temperature over the range 10 to 30°C has been considered not to have had a significant influence on the observed solubility of the test material.

Additionally, an assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 indicated observed solubilities and final solution pH’s similar to those obtained using unbuffered water. Thus, it can be anticipated that the water solubility of the test material over the pH range 4 to 9 would be constant, essentially due to the low buffering activities seen in the environment.

Description of key information

One key study exists. This study was performed in accordance with an accepted method (EU Method A.6) and under the conditions of GLP. 
This study is considered to be appropriate and reliable for use as a key study in accordance with Regulation (EC) No. 121907/2006 (REACH). No further testing is required.

Key value for chemical safety assessment

Water solubility:

10 000 mg/L

at the temperature of:

20 °C

Additional information

Method

The determination was carried out by visual assessment using a flask method, based on Method A6 Water Solubility of Commission Regulation (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 65.0 % w/w to 67.5 % w/w	>14
20.0±0.5°C	In the range 62.4 % w/w to 65.0 % w/w	>14
10.0±0.5°C	In the range 62.7 % w/w to 65.6 % w/w	>14

Overall, the effect of temperature over the range 10 to 30°C has been considered not to have had a significant influence on the observed solubility of the test material.

Additionally, an assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 indicated observed solubilities and final solution pH’s similar to those obtained using unbuffered water. Thus, it can be anticipated that the water solubility of the test material over the pH range 4 to 9 would be constant, essentially due to the low buffering activities seen in the environment.

Additional supporting studies that confirm the high solubility of the material are also provided.