Aluminium metaphosphate

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 2014 - March 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen

Type of method:

other: mass spectrometry

Water solubility:

4.575 µg/L

Temp.:

21.5 °C

pH:

8

Remarks on result:

other: Dissolved aluminium concentrations at loading of 1 mg/L of test item after 24 h (1d)

Water solubility:

13.81 µg/L

Temp.:

21.5 °C

pH:

8

Remarks on result:

other: Dissolved aluminium concentrations at loading of 1 mg/L of test item after 168 h (7d)

Water solubility:

35.78 µg/L

Temp.:

21.5 °C

pH:

8

Remarks on result:

other: Dissolved aluminium concentrations at loading of 1 mg/L of test item after 672 h (28 d)

Method validation summary (ICP-OES)

validation parameter	results	Comment
selectivity	selective wavelength of 167.019 nm for detection and evaluation of Al	no interferences observed
linearity	applied calibration functions were linear	correlation factor at least 0.999974
limit of detection	0.163 — 0.483 µg Al/L
limit of quantification	0.489 – 1.451 µg Al/L
accuracy and precision, reproducibility	mean recovery for diluted CRM TMDA-53.3 (36.3 µg Al/L): 105 ± 2 % (n = 11)	for concentration range
accuracy and precision, reproducibility	mean recovery for diluted CRM TM-15.2 (11.3 µg Al/L): 99.1 ± 3.0 % (n = 11)	for concentration range
accuracy and precision, reproducibility	mean recovery for multielement standard VIII (100 µg Al/L): 102 ± 2 % (n = 11)	for concentration range
accuracy and precision, reproducibility	mean recovery for recalibration standard (75 µg Al/L): 102 ± 2 % (n = 11)	for low concentration range
trueness	fortification of samples: 91.0 — 99.8 % (n = 6)

 

Test

During the test a background concentration of aluminium in the method blanks was observed. At each sampling point these concentrations were quite similar in the triplicate vessels and duplicate samples per flask. All calculated within- and between vessel variations of these concentrations (except method blank 1 from day 1: within vessel variation of 15.3%) were below 10 % and 20 %, respectively. The OECD Series 29 requires a limit of 20 % and 10 % for the between-vessel and the within-vessel variation, respectively. Therefore, these concentrations can be accepted as the aluminium background in all vessels (test flasks and method blanks) and it is feasible to subtract the mean values per sampling from the measured aluminium concentrations in the vessels containing test item.

Dissolved Al concentrations in test with the loading of 1 mg/L at pH 8 without subtraction the background concentrations.

 

sample name and day	Al conc. [µg/L]	mean Al conc. Per vessel [µg/L]	SD Al conc. per vessel [µg/L]	within vessel variation [%]	mean Al conc. All samples [µg/L]	SD Al conc. All samples [µg/L]	between vessel variation [µg/L]	difference between samplings [%]
1 a d 1	7.627
1 b d 1	7.480	7.554	0.104	1.4
2a d1	7.816
2b d1	7.458	7.637	0.253	3.3
3a d1	7.278
3b d1	6.863	7.070	0.294	4.2	7.420	0.327	4.4
1a d7	18.97
1 b d7	19.63	19.30	0.47	2.5
2a d7	18.69
2b d7	18.62	18.65	0.05	0.2
3a d7	18.36
3b d7	17.36	17.86	0.70	3.9	18.60	0.75	4.0	150.7
1a d28	45.90
1 b d28	45.94	45.92	0.03	0.1
2a d28	48.23
2b d28	47.38	47.80	0.60	1.3
3a d28	45.64
3b d28	45.32	45.48	0.22	0.5	46.40	1.14	2.5	149.4

 

 

Al in method blanks at pH 8 (BW — method blank; 1, 2, 3 — triplicate vessels; a, b – duplicate samples)

sample name and day	Al conc. [µg/L]	mean Al conc. Per vessel [µg/L]	SD Al conc. per vessel [µg/L]	within vessel variation [%]	mean Al conc. All samples [µg/L]	SD Al conc. All samples [µg/L]	between vessel variation [µg/L]	difference between samplings [%]
BW 1 a d1	2.406
BW 1 b d1	2.992	2.699	0.414	15.3
BW 2a d1	2.682
BW 2b d1	2.771	2.726	0.063	2.3
BW 3a d1	3.261
BW 3b d1	2.960	3.110	0.213	6.8	2.845	0.294	10.3
BW 1a d7	5.041
BW 1 b d7	4.549	4.795	0.347	7.2
BW 2a d7	4.512
BW 2b d7	4.489	4.501	0.017	0.4
BW 3a d7	5.344
BW 3b d7	4.816	5.080	0.373	7.3	4.792	0.345	7.2	68.4
BW 1a d28	10.65
BW 1 b d28	10.63	10.64	0.02	0.2
BW 2a d28	10.03
BW 2b d28	10.03	10.03	< 0.01	< 0.1
BW 3a d28	10.99
BW 3b d28	11.40	11.19	0.29	2.6	10.62	0.54	5.1	121.6

 

Dissolved Al concentrations in test with the loading of 1 mg/L at pH 8 minus mean Al background concentrations

Sample name and day	Al conc. Mean background [µg/L]	mean Al conc. Per vessel [µg/L]	SD Al conc per vessel – mean background [µg/L]	within vessel variation [%]	mean Al conc. All samples – mean background [µg/L]	SD Al conc. All samples – mean background [µg/L]	between vessel variation [%]	difference between samplings [%]
1 a d 1	4.782
1 b d 1	4.635	4.708	0.104	2.2
2a d 1	4.970
2b d1	4.612	4.791	0.253	5.3
3a d1	4.433
3b d1	4.017	4.225	0.294	7.0	4.575	0.327	7.2
1a d7	14.17
1 b d7	14.84	14.51	0.47	3.3
2a d7	13.89
2b d7	13.83	13.86	0.05	0.3
3a d7	13.57
3b d7	12.57	13.07	0.70	5.4	13.81	0.75	5.4	201.9
1a d28	35.28
1 b d28	35.32	35.30	0.03	0.1
2a d28	37.61
2b d28	36.76	37.18	0.60	1.6
3a d28	35.02
3b d28	34.70	34.86	0.22	0.6	35.78	1.14	3.2	159.0

 

The observed variations within and between test vessels (before and after blank subtraction) and within and between method blanks are in compliance with the test guideline after 24, 168 and 672 hours.

Aluminium recoveries for the test with 1 mg/L ranged from of 99.5 to 107 % (Table 12).Rinsing of filters was not necessary because Al was fully recovered (QA/QC requirements 100 ± 15 %)

Conclusions:

Interpretation of results (migrated information): insoluble (< 0.1 mg/L)

Description of key information

Dissolved aluminium metaphosphate type B (OECD 105, flask method):
0.0266 g/L at pH 4, 20 °C
0.0315 g/L at pH 7, 20 °C
0.0842 g/L at pH 9, 20 °C
Dissolved aluminium metaphosphate type A (OECD 105, flask method):
0.0073 g/L at pH 4, 20 °C
0.00474 g/L at pH 7, 20 °C
0.0191 g/L at pH 9, 20 °C
Dissolved aluminium concentrations at pH 8.0 at 21.5 °C (OECD 29):
- At loading rate of 1 mg/L test item: 4.575 µg/L after 24 h (1 d)
- At loading rate of 1 mg/L test item: 13.81 µg/L after  168 h (7 d)
- At loading rate of 1 mg/L test item: 35.78 µg/L after 672 h (28 d)

Key value for chemical safety assessment

Water solubility:

0.032 g/L

at the temperature of:

20 °C

Additional information

The water solubility of aluminium metaphosphate, in the sense of the standard method OECD 105, ranges from 0.0191 to 0.0842 g/L and is dependent on the media pH and on the manufacturing process. 0.0315 g/L is relevant to assess chemical safety since it represents the maximum solubility at a neutral pH.

Additionally, solubility of the test item in media simulating environmental conditions had been produced (in accordance with OECD 29) with loadings of 1 mg/L at a pH maximising the transformation/dissolution process (pH 8). Under these conditions, in the long range (28 days) aluminium metaphosphate shows a solubility of 35.78 µg/L.