Pentacalcium hydroxide tris(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 01 October 2009 and 14 November 2009.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. Study is conducted to an appropriate guideline, raw data is provided and therefore the study is considered to be acceptable for assessment and use as a key 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 September 2009 Date of Signature: 26 November 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:

6.57 mg/L

Temp.:

20 °C

pH:

> 7.2 - < 7.4

Details on results:

Please see section Remarks on results including tables and figures.

See attached file for typical chromatograms.

            

Results:

Preliminary test:

Un-buffered glass double-distilled water

The preliminary estimate of water solubility, as equivalent test material concentration, was 8.62 x 10^-3 g/l, with a final sample solution pH of 7.3.

pH 4 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 0.541 g/l, with a final sample solution pH of 5.4. Calculations were performed from the sample solutions diluted by a factor of 50 for analysis.

pH 9 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 1.81 x 10^-2 g/l, with a final sample solution pH of 8.9. Calculations were performed from the sample solutions diluted by a factor of 2 for analysis.

         

Definitive test:

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

Un-buffered glass double-distilled water

Solution	Area
Standard 20.6 mg/l	1.527
Standard 19.8 mg/l	1.493
Matrix blank	6.075 x 10^-2[1]
Sample 1A	0.328
Sample 1B	0.285
Sample 2A	0.296
Sample 2B	0.278

 

Un-buffered glass double-distilled water (continued)

Solution	Area
Sample 3A	0.266
Sample 3B	0.285
Sample 4A	0.268
Sample 4B	0.259
Sample 5A	0.268
Sample 5B	0.274

pH 4 buffer solution

Solution	Area
Standard 40.8 mg/l	3.091
Standard 40.0 mg/l	3.039
Matrix blank	none detected
Sample 1A	1.369
Sample 1B	1.358

pH 9 buffer solution

.

Solution	Area
Standard 19.2 mg/l	1.377
Standard 21.2 mg/l	1.562
Matrix blank	none detected
Sample 1A	0.325
Sample 1B	0.315

 

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

Un-buffered glass double-distilled water

Sample  Number	Time Shaken at ~ 30ºC (hours)	Equilibration Temperature (°C)	Equilibration Time (hours)	Equivalent Test Material Concentration (g/l)	Solution pH
1	24	20	24	7.05 x 10^-3	7.2
2	48	20	24	6.49 x 10^-3	7.3
3	72	20	24	6.17 x 10^-3	7.3
4	72	30	24	5.82 x 10^-3	7.4
5	72	10	24	6.05 x 10^-3	7.3

Mean concentration:6.57 x 10^-3 g/l at 20.0 ± 0.5ºC (samples 1 to 3 inclusive only)
Range:                             6.17 x 10^-3 to 7.05 x 10^-3 g/l (samples 1 to 3 inclusive only)

pH 4 buffer solution

Sample  Number	Time Shaken at ~ 30ºC (hours)	Equilibration Temperature (°C)	Equilibration Time (hours)	Equivalent Test Material Concentration (g/l)	Solution pH
1	72	20	24	0.483	5.5

pH 9 buffer solution

Sample  Number	Time Shaken at ~ 30ºC (hours)	Equilibration Temperature (°C)	Equilibration Time (hours)	Equivalent Test Material Concentration (g/l)	Solution pH
1	72	20	24	9.45 x 10^-3	9.0

[1]A minor artefact peak was observed on analysis of the matrix blank. All relevant standard and sample phosphate peak areas were corrected for this response prior to any further calculations.

Conclusions:

Interpretation of results (migrated information): slightly soluble (0.1-100 mg/L)
The ion chromatography method applied directly quantified the dissolved phosphate content of each sample solution and these have been corrected to equivalent test material concentrations based on the theoretical phosphate content of the test material. The water solubility of the test material has been determined to be 6.57 x 10-3 g/l of solution at 20.0 ± 0.5°C in un-buffered glass double-distilled water, resulting in sample solution pH’s in the range 7.2 to 7.4. The temperature range of 10°C to 30°C was shown not to have a significant influence on the water solubility of the test material (range 5.82 x 10-3 to 6.17 x 10-3 g/l). However solubility was identified as being significantly influenced by solution pH. Although solubility at pH 9 was approximately equal to that determined at a neutral pH (9.45 x 10-3 g/l at pH 9.0), a significant increase was observed at pH 4, with a solubility of 0.483 g/l being determined. An increase in solution pH to 5.5 was observed on dissolution of the test material in the pH 4 buffer solution, so potentially solubility may increase further in cases where additional buffering capacity exists.
The required quality criteria (validity, reliability, & repeatability) have been fulfilled by this study.

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:

Testing was performed using the flask method, Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008. The ion chromatography method applied directly quantified the dissolved phosphate content of each sample solution and these have been corrected to equivalent test material concentrations based on the theoretical phosphate content of the test material.The water solubility of the test material has been determined to be 6.57 x 10^-3 g/l of solution at 20.0 ± 0.5°C in un-buffered glass double-distilled water, resulting in sample solution pH’s in the range 7.2 to 7.4. The temperature range of 10°C to 30°C was shown not to have a significant influence on the water solubility of the test material (range 5.82 x 10^-3to 6.17 x 10^-3g/l). However solubility was identified as being significantly influenced by solution pH. Although solubility at pH 9 was approximately equal to that determined at a neutral pH (9.45 x 10^-3g/l at pH 9.0), a significant increase was observed at pH 4, with a solubility of 0.483 g/l being determined. An increase in solution pH to 5.5 was observed on dissolution of the test material in the pH 4 buffer solution, so potentially solubility may increase further in cases where additional buffering capacity exists.

Description of key information

 Water solubilty: 0,00657 g/L at 20°C (EU Method A.6, GLP)

Key value for chemical safety assessment

Water solubility:

0.007 g/L

at the temperature of:

20 °C

Additional information

Testing was performed using the flask method, Method A6 Water Solubility of Commission Regulation (EC) No 440/2008 of 30 May 2008.