Dipotassium hydrogenorthophosphate

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 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:

no

GLP compliance:

yes (incl. QA statement)

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:

63 - 65 other: %w/w

Temp.:

20 °C

pH:

> 10.1 - < 10.7

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:

Sample Identity	Concentration (% w/w)	Observations	Solution pH
1	12.5	Test material fully dissolved.	9.2
2	20.4	Test material fully dissolved.	9.3
3	30.1	Test material fully dissolved.	9.4
4	40.8	Test material fully dissolved.	9.7
5	50.7	Test material fully dissolved.	9.8
6	60.1	Clear colourless, slightly viscous solution with no excess undissolved test material.	10.0
7	70.7	Mixture consisting of a clear colourless liquid with excess undissolved test material.	10.5
8	80.2	Wet white solid.	*
9	89.9	Slightly damp white solid.	*

Preliminary result:    20°C: In the range 60.1 % w/w to 70.7 % w/w      

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

Definitive test

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

Sample Identity	Concentration (% w/w)	Observations	Solution pH
18	59.8	Clear colourless liquid with no evidence of undissolved test material.	10.5
19	62.2	Clear colourless liquid with no evidence of undissolved test material.	10.6
20	64.6	Clear colourless liquid with no evidence of undissolved test material.	10.7
21	67.6	Contains undissolved excess test material.	*
22	69.7	Contains undissolved excess test material.	*

Sample Identity	Concentration (% w/w)	Observations	Solution pH
10	63.0	Clear colourless liquid with no evidence of undissolved test material.	10.1
11	65.0	Contains undissolved excess test material.	*
12	67.7	Contains undissolved excess test material.	*
23	66.7	Contains undissolved excess test material.	*
24	67.0	Contains undissolved excess test material.	*

Sample Identity	Concentration (% w/w)	Observations	Solution pH
13	60.2	Clear colourless liquid with no evidence of undissolved test material.	10.5
14	62.8	Clear colourless liquid with no evidence of undissolved test material.	10.6
15	64.9	Contains undissolved excess test material.	*
16	67.3	Contains undissolved excess test material.	*
17	69.4	Contains undissolved excess test material.	*

Overall results:          30°C: In the range 64.6 % w/w to 67.6 % w/w
                                  20°C: In the range 63.0 % w/w to 65.0 % w/w
                                  10°C: In the range 62.8 % w/w to 64.9 % w/w

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

Additional Test

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

Sample Identity	Concentration (% w/w)	Observations	Solution pH
25	50.5	Clear colourless liquid with no evidence of undissolved test material.	10.3
26	50.9	Clear colourless liquid with no evidence of undissolved test material.	10.3

Results:         In the range 50.5 % w/w to 67.0 % w/w, using the pH 4 buffer solution; in the range 50.9 % w/w to 66.7 % 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. The results are shown in the following table:
Test temperatureWater solubilityTypical solution pH
30.0°C In the range 64.6 % w/w to 67.6 % w/w10.7
20.0°C In the range 63.0 % w/w to 65.0 % w/w10.1
10.0°C In the range 62.8 % w/w to 64.9 % w/w10.6

Overall, the effect of temperature over the range 10 to 30°Chas 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.

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:

The water solubility of the test material was determined by visual assessment using a flask method, based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.  The results are shown in the following table:

Test temperature	Water solubility	Typical solution pH
30.0±0.5°C	In the range 64.6 % w/w to 67.6 % w/w	10.7
20.0±0.5°C	In the range 63.0% w/w to 65.0 % w/w	10.1
10.0±0.5°C	In the range 62.8% w/w to 64.9 % w/w	10.6

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. The water solubility of dipotassium hydrogenorthophosphate 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 was determined by visual assessment using a flask method, based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.  The results are shown in the following table:

Test temperature	Water solubility	Typical solution pH
30.0±0.5°C	In the range 64.6 % w/w to 67.6 % w/w	10.7
20.0±0.5°C	In the range 63.0% w/w to 65.0 % w/w	10.1
10.0±0.5°C	In the range 62.8% w/w to 64.9 % w/w	10.6

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.