Pentapotassium triphosphate

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 23 October 2009 and 12 June 2010.

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:

UK GLP standards (Schedule 1, Good Laboratory Practice Regulations 1999 (SI 1999/3106 as amended by SI 2004/0994)). These Regulations are in accordance with GLP standards published as OECD Principles on Good Laboratory Practice (revised 1997, ENV/MC/CHEM

Type of method:

flask method

Water solubility:

45.7 other: % w/w

Temp.:

20 °C

pH:

9.1

Remarks on result:

other: The solubility of the test material was considered to be independent of both pH and temperature.

Details on results:

Please see "Any other information on results" section as these are mostly tables.

Results

Preliminary testing (Visual assessment)

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

Observations after Equilibration at 30°C

Sample Identity	Concentration (% w/w)	Observations
1	30.1	A hazy solution containing excess, un-dissolved test material at the base of the vessel.
2	40.0	A hazy solution containing excess, un-dissolved test material at the base of the vessel.
3	50.0	A hazy solution containing excess, un-dissolved test material at the base of the vessel.
4	59.9	A hazy solution containing excess, un-dissolved test material at the base of the vessel.
5	69.9	No visible solution, with all water absorbed to give a block of solid 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	30.1	9.4
2	40.0	9.6
3	50.0	9.8
4	59.9	10.1
5	69.9	10.4

Preliminary test result:        Solubility at 30.0°C: Less than 30.1% w/w (by visual assessment)

Preliminary testing (with ion chromatography analysis)

Un-buffered glass double-distilled water

The preliminary estimate of water solubility, as equivalent test material concentration, was 269 g/l, with a final sample solution pH of 9.3.

pH 4 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 255 g/l, with a final sample solution pH of 9.2.

pH 9 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 262 g/l, with a final sample solution pH of 9.3. 

Definitive test

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

Solution	Area
Standard 22.2 mg/l	2.015
Standard 20.3 mg/l	1.882
Matrix blank	none detected
Sample 1A	3.146
Sample 1B	3.093
Sample 2A	3.133
Sample 2B	3.164
Sample 3A	3.095
Sample 3B	3.122
Sample 4A	3.146
Sample 4B	3.144
Sample 5A	2.718
Sample 5B	2.758

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

Sample  Number	Time Shaken at ~ 30ºC (hours)	Equilibration Temperature (°C)	Equilibration Time (hours)	Equivalent Test Material Concentration (% w/w)	Solution pH
1	24	20	24	45.5	9.1
2	48	20	24	46.3	9.1
3	72	20	24	45.3	9.1
4	72	30	24	46.0	9.1
5	72	10	24	41.7	9.0

Mean concentration:45.7% w/w at 20.0 ± 0.5ºC (samples 1 to 3 inclusive only)
Range:                                   45.3 to 46.3% w/w (samples 1 to 3 inclusive only)

Validation

The linearity of the detector response with respect to concentration was assessed over the nominal standard concentration range of 0 to 75 mg/l, equivalent to approximately 0 to 44 mg/l as the triphosphate anion. This was satisfactory with a correlation coefficient of 1.000 being obtained. 

Conclusions:

Interpretation of results (migrated information): very soluble (> 10000 mg/L)
The ion chromatography method applied directly quantified the dissolved triphosphate content of each sample solution and these have been corrected to equivalent test material concentrations based on the theoretical triphosphate content of the test material. The water solubility of the test material has been determined to be 45.7% w/w of solution at 20.0 ± 0.5°C in un-buffered glass double-distilled water, resulting in a sample solution pH of 9.1.

Investigation into the influence of the pH range 4 to 9 on the solubility of the test material was performed but in each case the test material demonstrated moderately basic characteristics and a significant buffering effect on dissolution, overwhelming the capacity of the buffer solutions to give solution pH’s and solubility results approximately equal to those observed in un-buffered water. Therefore, as the buffering capacity of the solutions used were considered to exceed that of the environment, the solubility of the test material was considered to be independent of the initial pH range 4 to 9, resulting in a consistent basic pH solution capable of overwhelming any weak to moderate buffering capacities present.

The temperature range of 10°C to 30°C was also shown not to have a significant influence on the water solubility of the test material (range 41.7 to 46.0% w/w).
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:

Summary

The water solubilty testing was performed using a flask method based on Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008. The ion chromatography method applied directly quantified the dissolved triphosphate content of each sample solution and these have been corrected to equivalent test material concentrations based on the theoretical triphosphate content of the test material.The water solubility of the test material has been determined to be 45.7% w/w of solution at 20.0 ± 0.5°C in un-buffered glass double-distilled water, resulting in a sample solution pH of 9.1.

Investigation into the influence of the pH range 4 to 9 on the solubility of the test material was performed but in each case the test material demonstrated moderately basic characteristics and a significant buffering effect on dissolution, overwhelming the capacity of the buffer solutions to give solution pH’s and solubility results approximately equal to those observed in un-buffered water. Therefore, as the buffering capacity of the solutions used were considered to exceed that of the environment, the solubility of the test material was considered to be independent of the initial pH range 4 to 9, resulting in a consistent basic pH solution capable of overwhelming any weak to moderate buffering capacities present.

The temperature range of 10°C to 30°C was also shown not to have a significant influence on the water solubility of the test material (range 41.7 to 46.0% w/w). 

Description of key information

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

Additional information

The ion chromatography method applied directly quantified the dissolved triphosphate content of each sample solution and these have been corrected to equivalent test material concentrations based on the theoretical triphosphate content of the test material. The water solubility of the test material has been determined to be 45.7% w/w of solution at 20.0 ± 0.5°C in un-buffered glass double-distilled water, resulting in a sample solution pH of 9.1.