Strontium

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-08-30 to 2016-10-04

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:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one single vessel at each point in time

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

2008

Deviations:

yes

Remarks:

Two vessels were set up in a parallel design, each vessel was sampled several times instead of sampling one single vessel at each point in time

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2016-05-31

Type of method:

flask method

Key result

Water solubility:

6.74 g/L

Conc. based on:

test mat.

Loading of aqueous phase:

41 g/L

Incubation duration:

>= 20 - <= 22 d

Temp.:

20 °C

pH:

>= 13.2 - <= 13.3

Remarks on result:

other: SD: 0.14 g Sr/L

Details on results:

Temperature: The temperature in the thermostatically controlled incubation cabinet was monitored by a thermo data logger (Testo 175-T2. Testo AG. Leutkirch. Germany). The mean temperature was 20.3 ± 0.2 °C.Solution pHThe pH of solutions containing the test item increased to a pH > 13 immediately upon contact with the test item and further up to 13.6 but stabilized at a pH of 13.2 – 13.3 after 3 days of testing. The pH of method blanks remained at 6.7 – 7.0.Oxygen concentrationDuring 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 %.TurbidityThe turbidity of filtered samples was measured using a Nanocolor 500D photometer (Macherey Nagel, Dueren, Germany) according to ISO 7027 to confirm that measured strontium concentrations correspond to the dissolved fraction. Measured values below 1 FAU (formazine attenuation units) were not further specified and reported as <1 FAU. However, turbidity of ultrapure water is <1 FAU, whereas turbidity of tap water amounts to 2 FAU. The turbidity in samples from test was always <1 FAU indicating that filtered solutions did not contain any undissolved material

Method validation summary

validation parameter	results	comment
selectivity	strontium-selective wavelengths of 216.596 nm and 215.284 nm	no matrix effects observed
linearity	applied calibration functions were linear	correlation coefficients were 0.999995 (pre-test) 0.999707 and 0.999393 (main test)
limit of detection (LOD)	pre-test: 0.305 µg Sr/L main test: 19.1 – 20.3 µg Sr/[AV3] L
limit of quantification (LOQ)	pre-test: 0.914 µg Sr/L main test: 63.3 – 67.8 µg Sr/L[AV4]
method blanks	main test: Sr concentrations < LOD (<20.3 – 28.5 µg Sr/L)	method blanks
accuracy and precision	mean Sr recovery in CRM TM-26.4: pre-test: 94.4 ± 2.9 % (n = 2)	106 µg Sr/L
accuracy and precision; repeatability	mean Sr recovery in CRM TM-54.5 (dilution 3 fold) main test (216.596 nm): 106.7 ± 9.3 % (n = 3) main test (215.284 nm): 110.5 ± 2.1 % (n = 3)	197 µg Sr/L
accuracy and precision; repeatability	mean Sr recovery in Multi-Element Standard XXI: main test (216.596 nm): 106.2 ± 5.5 % (n = 2) main test (215.284 nm): 113.1 ± 2.2 % (n = 3)	500 µg Sr/L
accuracy and precision; repeatability	mean Sr recovery in recalibration standard main test (216.596 nm): 104.6 ± 9.4 % (n = 3) main test (215.284 nm): 112.3 ± 2.1 % (n = 3)	500 µg Sr/L
trueness	main test: Sr recoveries in fortified samples: 104.6 – 108.3 % (n = 3)

Under the conditions of this test (flask method under protective gas atmosphere; loadings of 41.01 g test item/L and 41.04 g test item/L in vessel 1 and 2, respectively), a solubility equilibrium was observed starting on day 20 and the test was determined on day 22. The mean amount of dissolved strontium at 20.0 ± 1.0 °C as measured on day 20, 21 and 22 amounts to 6.74 ± 0.14 g Sr/L (separated by filtration from undissolved test item). After introducing the test item into the argon-purged water in test vessels, an evolution of gas (presumably hydrogen) was observed. The pH of solutions containing the test item increased to a pH > 13 immediately upon contact with the test item and further up to 13.6 but stabilized at a pH of 13.2 – 13.3 after 3 days of testing. The pH of method blanks remained constant at 6.7 – 7.0.

Conclusions:

According to OECD guideline 105 (1995) and EU method A.6 (2006), the water solubility of strontium was determined with 6.74 ± 0.14 g/L, under the conditions of this test (flask method under protective gas atmosphere; loading of 41 g Sr/L, at 20.0 ± 1.0 °C, pH >13).

Description of key information

Klawonn, 2016:

 Strontium metal is highly reactive and instantly oxidized upon contact with water. It decomposes completely. During the redox-reaction with water, a strong evolution of hydrogen gas and an immediate precipitation of a white, crystalline solid (i.e. Sr(OH)2 is observed. The amount of dissolved Sr cations is determined by the solubility of the Sr(OH)2 precipitate. According to OECD guideline 105 (1995) and EU method A.6 (2006), the water solubility of strontium was determined to be 6.74 ± 0.14 g/L under the conditions of the test (flask method under protective gas atmosphere; loading of 41 g Sr/L, at 20.0 ± 1.0 °C, pH >13)

Key value for chemical safety assessment

Water solubility:

6.74 g/L

at the temperature of:

20 °C