Potassium 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 30 September 2009 and 24 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: 15-09-2009 Date of Signature: 26-11-2009

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:

208 g/L

Temp.:

20 °C

pH:

>= 4.2 - <= 4.5

Details on results:

Please see section Remarks on results including tables and figures.

Results

Preliminary test

The mean peak areas relating to the standard and sample solutions are shown in the following table:

Table 6.6

Solution	Mean peak area*
Standard 30.0 mg/l	3.092
Standard 30.1 mg/l	3.239
Sample 1C**	1.598
Sample 2C**	1.765

*corrected for the relevant blank

**trial injections carried out prior to the run indicated that Samples 1A, 1B, 2A and 2B were well outside the linearity range; therefore, these solutions were not analysed in full

The concentration (g/l) of test material in the sample solutions is shown in the following table:

Table 6.7

Sample Number	Time shaken at ~ 30ºC (hours)	Time equilibrated at 20ºC (hours)	Concentration (g/l)	Solution pH
1	18¼	5	~218	4.3
2	18¼	5	~240	4.3

Consequently, as the use of the pH 4 buffer had no real effect on the pH of the solutions, it was considered that the effect in the environment would be negligible, essentially due to the low buffering activities seen there.

Definitive test

The mean peak areas relating to the standard and sample solutions are shown in the following table:

Table 6.8

Solution	Mean peak area
Standard 30.1 mg/l	3.877
Standard 30.0 mg/l	3.837
Sample 5A	3.529
Sample 5B	3.498
Sample 4A	3.887
Sample 4B	3.816
Sample 3A	3.798
Sample 3B	3.806
Standard 30.1 mg/l	3.901
Standard 30.0 mg/l	3.842
Sample 7A	3.131
Sample 7B	3.099
Sample 6A	4.319
Sample 6B	4.301
Sample 8A	3.864
Sample 8B	3.877

The concentration (g/l) of test material in the sample solutions is shown in the following table:

Table 6.9

Sample Number	Time shaken at ~ 30ºC (hours)	Time equilibrated at 20ºC (hours)	Concentration (g/l)	Solution pH
3	72	24	212	4.5
4	48	24	215	4.2
5	24	24	196	4.2
6	72	24 (30°C)	239	4.3
7	72	24 (10°C)	173	4.2
8	72	24	215	4.2

Consequently, as the use of the pH 9 buffer had no real effect on the pH of the solutions, it was considered that the effect in the environment would be negligible, essentially due to the low buffering activities seen there.

Validation

The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 0 to 100 mg/l*. This was satisfactory with a correlation coefficient of 1.000 being obtained. This work was performed as part of Harlan Laboratories Ltd Project Number 2920/0020.

*as the orthophosphate anion

Conclusions:

Interpretation of results: very soluble (> 10000 mg/L)
The water solubility of the test material has been determined to be 208 g/l of solution at 20.0 ± 0.5°C.
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 (range 173 to 239 g/l).
An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 gave solubility results 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:

Method

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

The water solubility of the test material has been determined to be 208 g/l of solution at 20.0±0.5°C.

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 (range 173 to 239 g/l).

An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 gave solubility results 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 potassium dihydrogenorthophosphate was determined according to EU Method A.6 (Water solubility) and under the conditions of GLP. 

Key value for chemical safety assessment

Water solubility:

208 g/L

at the temperature of:

20 °C

Additional information

The water solubility of the test material has been determined to be 208 g/l of solution at 20.0 ± 0.5°C.

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 (range 173 to 239 g/l).

An assessment of the solubility of the test material over the environmentally relevant pH range of 4 to 9 gave solubility results 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.