Aluminium lanthanum trioxide

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-07-22 to 2016-08-29

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

1995

Deviations:

yes

Remarks:

see "Principles of method if other than guideline"

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

2008

Deviations:

yes

Remarks:

see "Principles of method if other than guideline"

Principles of method if other than guideline:

The test was performed according to the OECD-Guideline for Testing of Chemicals No. 105, Water Solubility, flask method with the following modifications:
- Two vessels were set up in a parallel design at 20.0 °C, each vessel was sampled several times instead of sampling just one vessel every time or setting up individual vessels that are sampled only once. This modification helps avoiding weighing errors and enables several samplings from two vessels, i.e., solubility measurements from two individual flasks at each defined time point. The avoidance of weighing errors and the repeated sampling from two separate vessel at each time point (as described above) helps generating more accurate and precise test results.
- The study was performed under inert gas (argon) and under exclusion of atmospheric oxygen and carbon dioxide.
- Constant concentrations (i.e. “[…] concentrations measured in at least the two last [… sampling points] do not differ by more than 15 %”), could not be measured over the course of the test for all metals. Dissolved aluminium concentrations decreased whereas lanthanum concentrations varied during the test.

GLP compliance:

yes (incl. QA statement)

Remarks:

2016-05-31

Type of method:

flask method

Key result

Water solubility:

< 0.05 mg/L

Conc. based on:

element (dissolved fraction)

Remarks:

Al and La

Loading of aqueous phase:

100 mg/L

Incubation duration:

>= 5 - <= 34 d

Temp.:

20 °C

pH:

>= 6.8 - <= 8.4

Remarks on result:

other: mean result from (i) filtration + centrifugal filtration

Details on results:

Temperature
The temperature in the thermostatically controlled water bath was monitored with a thermo data logger (Testo 175-T2, Testo AG, Leutkirch, Germany). The mean temperature was 19.6 ± 0.1 °C.

The pH
The pH of solutions containing the test item increased from 6.8 – 7.2 to 8.3 – 8.4 after 18 days of testing. Afterwards, the pH remained relatively stable at 8.2 – 8.3. The pH of method blanks ranged from 6.3 to 6.5, except for the pH in vessel 2 after 5 days (pH of 7.1), 6 and 7 days (pH of 7.8). However, the pH of the method blank in vessel 2 remained relatively stable at 6.4 – 6.6 after 18 days until the end of the test.

Oxygen concentration
During the test, the oxygen concentration in the acrylic glass box was monitored with a MICRO IV oxygen sensor prior and after sampling. Oxygen concentrations (in %) remained at about 0 %.

Turbidity
Since the sampling volume was limited, the turbidity was measured on each sampling date only in samples filtered through a 0.2 µm membrane (additional 10 mL). The turbidity of the respective centrifugal filtered test sample and method blank was only measured on day 5 with 0.02 NTU.
The turbidity was recorded for all 0.2 µm filtered samples. Turbidity of drinking water should not be > 5 NTU and should ideally be < 0.1 NTU for an effective disinfection. Thus, based on the turbidity measurement, the solution samples were clear.

Under the conditions of this test (flask method; loadings of 100.036 mg/L and 100.018 mg/L in vessel 1 and 2), a solubility equilibrium was not observed during the test period of 34 days. Slightly higher aluminium and lanthanum concentrations were measured in solutions filtered only through a 0.2 µm membrane in comparison to concentrations of solutions applied to centrifugal filtration. This may indicate that smaller particles (i.e. < 0.2 µm but > 3 kDa) are present in solutions filtered through a 0.2 µm membrane. Thus, aluminium and lanthanum concentrations measured in the fraction < 3 kDa are operationally defined as “dissolved concentrations”. 

Measured aluminium and lanthanum concentrations of test solutions are compiled in following tables.

Mean aluminium concentrations of solutions containing the test item

A) Solutions after filtration through a 0.2 µm membrane and centrifugal filtration
Sampling [d]	Mean Al conc [µg/L]	Mean SD Al conc. [µg/L]	Variation between sampling intervals [%]	Mean Al conc. - background- corrected [µg/L]	Mean SD Al conc. [µg/L]	Variation betweensampling intervals - background-corrected[%]
5	47.52	17.81		46.49	17.81
6	56.73	26.03	19.4	55.18	26.03	18.7
7	33.82	14.62	-40.4	30.00	14.62	-45.6
18	11.77	15.33	-65.2	11.77	15.33	-60.8
19	4.95	5.69	-57.9	4.95	5.69	-57.9
20	<LOD (<1.32)			0.93*
32	32.70	15.72		32.70	15.72
33	31.06	10.30	-5.0	31.06	10.30	-5.0
34	at least <LOQ (<1.17)			0.40^#
B) Solutions after filtration through a 0.2 µm membrane
Sampling [d]	Mean Al conc [µg/L]	Mean SD Al conc. [µg/L]	Variation between sampling intervals [%]	Mean Al conc. - background- corrected [µg/L]	Mean SD Al conc. [µg/L]	Variation betweensampling intervals - background-corrected[%]
5	248.67	58.55		246.96	58.55
6	236.34	74.39	-5.0	235.24	74.39	-4.7
7	197.18	89.70	-16.6	194.71	89.70	-17.2
18	174.14	39.18	-11.7	174.14	39.18	-10.6
19	169.34	45.90	-2.8	169.34	45.90	-2.8
20	60.33	74.00	-64.4	60.33	74.00	-64.4
32	85.58	36.86	41.8	85.58	36.86	41.8
33	71.75	23.98	-16.2	71.75	23.98	-16.2
34	<LOD (<0.39)			0.28*

* All concentrations below LOD;^#All concentrations below LOD/LOQ

 

Mean lanthanum concentrations of solutions containing the test item

A) Solutions after filtration through a 0.2 µm membrane and centrifugal filtration
Sampling [d]	Mean La conc. [µg/L]	Mean SD La conc. [µg/L]	Variation between sampling intervals [%]
5	6.34	2.35
6	4.79	6.56	-24.5
7	12.76	17.46	166.7
18	0.07*
19	0.93	1.12
20	5.10	5.79	469.6
32	1.25	1.07	-75.5
33	0.79	0.92	-36.9
34	13.38	4.47	1598.7
B) Solutions after filtration through a 0.2 µm membrane
Sampling [d]	mean La conc. [µg/L]	mean SD La conc. [µg/L]	variation between sampling intervals [%]
5	5.11	7.02
6	13.61	19.04	166.2
7	24.98	34.73	83.5
18	0.22	0.21	-99.1
19	0.07*
20	9.73	13.36
32	0.20^#
33	0.25	0.07
34	24.20	26.74	9521.5

* All concentrations below LOD;^#All concentrations below LOQ

Mean measured dissolved aluminium and lanthanum concentrations fluctuate from < 1.17 µg Al/L to 56.73 µg Al/L (background-corrected) and < 0.10 µg La/L to 13.38 µg La/L during the 34-d test period. Based on means of dissolved Al and La concentrations (as measured on day 5, 6, 7, 18, 19, 20, 32, 33, 34) amounting to 24.25 ± 19.68 µg Al/L and 5.04 ± 5.06 µg La/L, solubility of aluminium lanthanum oxide is estimated with < 0.05 mg/L.

Method validation summary (dilution with 0.5 M nitric acid)

validation parameter	results	comment
selectivity	Aluminium at wavelengths 167.019 nm and 394.402 nm Lanthanum at wavelength 379.477 nm	no matrix effects observed
linearity	applied calibration functions were linear	correlation coefficient ≥ 0.999633
limits of detection (LOD)	Al: 0.0767 – 2.9037 µg/L La: 0.1004 – 0.2091 µg/L
limits of quantification (LOQ)	Al: 0.2301 – 8.7110 µg/L La: 0.3011 – 0.6272 µg/L
method blanks	Al: some method blanks >LOQ Measured test concentrations are reported without and with background correction La: Mostly <LOD, four method blanks <LOQ
accuracy and precision	mean recovery within measurement series for certified reference material TM-26.4: #1 measurement series: Al (167.019 nm): 91.9 ± 1.2 % (n = 3)	certified with 74 µg Al/L
accuracy and precision	mean recoveries within measurement series for certified reference material TMDA-52.4: #2 measurement series: Al (394.402 nm): 95.4 ± 1.0 % (n = 5) #3 measurement series: Al (167.019 nm):106.8 ± 1.0 % (n = 5)	certified with 61.2 µg Al/L (diluted 5 fold)
accuracy and precision	mean recovery within measurement series for multi element standard XXI: #1 measurement series: Al (167.019 nm): 94.5 ± 1.0 % (n = 3)	diluted to 100 µg Al/L
accuracy and precision	mean recoveries within measurement series for recalibration samples: #2 measurement series: Al (394.402 nm): 102.1 ± 0.6 % (n = 5) La (379.477 nm): 101.8 ± 0.4 % (n = 5) #3 measurement series: Al (394.402 nm): 104.0 ± 0.6 % (n = 5) La (379.477 nm): 102.7 ± 0.5 % (n = 5)	diluted to 100 µg Al and La/L
accuracy and precision	mean recovery within measurement series for recalibration samples: #1 measurement series: Al (167.019 nm): 98.5 ± 1.2 % (n = 3) La (379.477 nm): 101.1 ± 0.2 % (n = 3)	diluted to 50 µg Al and La/L
accuracy and precision	mean recovery within measurement series for recalibration samples: #1 measurement series: La (379.477 nm): 110.5 ± 0.1 % (n = 3)	diluted to 25 µg La/L
accuracy and precision	mean recovery within measurement series for recalibration samples: Non GLP preliminary test: Al (167.019 nm): 103.7 % (n = 1) La (379.477 nm): 106.7 % (n = 1)	diluted to 10 µg Al and La/L
accuracy and precision	mean recovery within measurement series for quality control single element standard La from CPI: #1 measurement series: La (379.477 nm): 109.1 ± 0.4 % (n = 3)	diluted to 25 µg La/L
accuracy and precision	mean recovery within measurement series for quality control single element standard La from CPI: #2 measurement series: La (379.477 nm): 100.3 ± 0.4 % (n = 5) #2 measurement series: La (379.477 nm): 106.6 ± 1.1 % (n = 5)	diluted to 50 µg La/L
trueness	recovery from fortification of samples: Al: 92.8 – 121.0 % (n = 8) La: 100.7 – 111.0 % (n = 8)	The recovery of Al in one sample (121.0 %) is not within the limits of 100 ± 15 %. Since recovery of 7 out of 8 fortified solutions is well within the limits, the analysis of Al concentrations is considered to be valid

Conclusions:

Under the conditions of this test (OECD 105 (1995) flask method; loadings of 100.036 mg/L and 100.018 mg/L in vessel 1 and 2), a solubility equilibrium was not observed during the test period of 34 days. Slightly higher aluminium and lanthanum concentrations were measured in solutions filtered only through a 0.2 µm membrane in comparison to concentrations of solutions applied to centrifugal filtration.
Mean measured dissolved aluminium and lanthanum concentrations fluctuate from < 1.17 µg Al/L to 56.73 µg Al/L (background-corrected) and < 0.10 µg La/L to 13.38 µg La/L during the 34-d test period.
Based on means of dissolved Al and La concentrations (as measured on day 5, 6, 7, 18, 19, 20, 32, 33, 34) amounting to 24.25 ± 19.68 µg Al/L and 5.04 ± 5.06 µg La/L, the water solubility of aluminium lanthanum trioxide is estimated with < 0.05 mg/L.

Description of key information

The waters solubility of aluminium lanthanum trioxide is estimated to be < 0.05 mg/L.

Additional information

Under the conditions of this test (OECD 105 (1995) flask method; loadings of 100.036 mg/L and 100.018 mg/L in vessel 1 and 2), a solubility equilibrium was not observed during the test period of 34 days. Slightly higher aluminium and lanthanum concentrations were measured in solutions filtered only through a 0.2 µm membrane in comparison to concentrations of solutions applied to centrifugal filtration.

Mean measured dissolved aluminium and lanthanum concentrations fluctuate from < 1.17 µg Al/L to 56.73 µg Al/L (background-corrected) and < 0.10 µg La/L to 13.38 µg La/L during the 34-d test period.

Based on means of dissolved Al and La concentrations (as measured on day 5, 6, 7, 18, 19, 20, 32, 33, 34) amounting to 23.72 ± 20.12 µg Al/L and 5.04 ± 5.06 µg La/L, the waters solubility of aluminium lanthanum trioxide is estimated with < 0.05 mg/L.