Aluminium 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 06 October 2009 and 25 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)

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:

<= 6.92 mg/L

Temp.:

20 °C

pH:

>= 6.6 - <= 7.1

Details on results:

Please see section Remarks on results including tables and figures.

      

SEE ATTACHMENT FOR TYPICAL CHROMATOGRAPHY

Preliminary testing:

Un-buffered glass double-distilled water

The preliminary estimate of water solubility, as equivalent test material concentration, was 4.55 x 10^-3 g/l, with a final sample solution pH of 5.6.

pH 4 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 1.57 x 10^-2 g/l, with a final sample solution pH of 4.1. Calculations were performed from the sample solutions diluted by a factor of 2 for analysis.

pH 9 buffer solution

The preliminary estimate of water solubility, as equivalent test material concentration, was 1.83 x 10^-2 g/l, with a final sample solution pH of 8.7. 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 20.0 mg/l	1.423
Standard 20.4 mg/l	1.459
Matrix blank	none detected
Sample 1A	0.174
Sample 1B	0.225
Sample 2A	0.316
Sample 2B	0.314

 

Un-buffered glass double-distilled water (continued)

Solution	Area
Sample 3A	0.135
Sample 3B	0.121
Sample 4A	0.188
Sample 4B	0.211
Sample 5A	0.163
Sample 5B	0.166

pH 4 buffer solution

Solution	Area
Standard 20.0 mg/l	1.414
Standard 20.4 mg/l	1.470
Matrix blank	none detected
Sample 1A	4.968
Sample 1B	5.018

pH 9 buffer solution

Solution	Area
Standard 20.0 mg/l	1.433
Standard 20.4 mg/l	1.462
Matrix blank	none detected
Sample 1A	0.932
Sample 1B	0.872

 

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	4.38 x 10^-3	6.6
2	48	20	24	6.92 x 10^-3	7.0
3	72	20	24	2.81 x 10^-3	7.1
4	72	10	24	4.38 x 10^-3	7.1
5	72	30	24	3.62 x 10^-3	7.0

Overall result:         ≤6.92 x 10^-3 g/l at 20.0 ± 0.5ºC (samples 1 to 3 inclusive only)
Range:                   2.81 x 10^-3 to 6.92 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	0.110	4.0

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	1.97 x 10^-2	8.4

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 less than or equal to 6.92 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 6.6 to 7.1. As limited but variable concentrations were determined for the three individual samples, the definitive test concentration range being 2.81 x 10-3 g/l to 6.92 x 10-3 g/l, an overall limit value has been reported as a worst case scenario for risk assessment. No correlation between initial saturation period and final test material concentration was observed, indicating that variation was not due to either hydrolysis or the failure of a saturation plateau to be achieved. 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, with concentrations of 4.38 x 10-3 g/l, 2.81 x 10 3 g/l and 3.62 x 10-3 g/l being determined at temperatures of 10°, 20°C and 30°C respectively failing to correlate with their final equilibration temperatures. However solubility was identified as being significantly influenced by solution pH. Although solubility at pH 9 was only approximately twice that observed in un-buffered water (1.97 x 10-2 g/l with a final solution pH of 8.4), a significant increase was observed at pH 4.0, with a solubility of 0.110 g/l being determined.

This 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 in accordance with Regulation (EC) No. 1907/2006 (REACH).

Executive summary:

Testing was performed using the flaskt 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 less than or equal to 6.92 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 6.6 to 7.1. As limited but variable concentrations were determined for the three individual samples, the definitive test concentration range being 2.81 x 10^-3 g/l to 6.92 x 10^-3g/l, an overall limit value has been reported as a worst case scenario for risk assessment. No correlation between initial saturation period and final test material concentration was observed, indicating that variation was not due to either hydrolysis or the failure of a saturation plateau to be achieved. 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, with concentrations of 4.38 x 10^-3g/l, 2.81 x 10^‑3 g/l and 3.62 x 10^-3g/l being determined at temperatures of 10°, 20°C and 30°C respectively failing to correlate with their final equilibration temperatures. However solubility was identified as being significantly influenced by solution pH. Although solubility at pH 9 was only approximately twice that observed in un-buffered water (1.97 x 10^-2g/l with a final solution pH of 8.4), a significant increase was observed at pH 4.0, with a solubility of 0.110 g/l being determined.

Description of key information

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

Key value for chemical safety assessment

Water solubility:

0.007 g/L

at the temperature of:

20 °C

Additional information

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 less than or equal to 6.92 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 6.6 to 7.1. As limited but variable concentrations were determined for the three individual samples, the definitive test concentration range being 2.81 x 10-3 g/l to 6.92 x 10-3 g/l, an overall limit value has been reported as a worst case scenario for risk assessment. No correlation between initial saturation period and final test material concentration was observed, indicating that variation was not due to either hydrolysis or the failure of a saturation plateau to be achieved. 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, with concentrations of 4.38 x 10-3 g/l, 2.81 x 10 3 g/l and 3.62 x 10-3 g/l being determined at temperatures of 10°, 20°C and 30°C respectively failing to correlate with their final equilibration temperatures. However solubility was identified as being significantly influenced by solution pH. Although solubility at pH 9 was only approximately twice that observed in un-buffered water (1.97 x 10-2 g/l with a final solution pH of 8.4), a significant increase was observed at pH 4.0, with a solubility of 0.110 g/l being determined.