Chrome tungsten titanium buff rutile

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

transformation / dissolution of metals and inorganic metal compounds

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020-11-30 to 2021-01-04

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: See "Remarks"

Remarks:

The present GLP guideline study provides valuable data on the transformation/dissolution behaviour of chrome tungsten titanium buff rutile in environmentally relevant media. The study however, despite the use of certified tungsten standards for calibration, lacks proper validation of the tungsten measurement series by measuring an additional independent certified reference material. Therefore, in regard to the tungsten measurements only, the study is rated “R2” (reliable with restrictions).

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

Principles of method if other than guideline:

The transformation/dissolution of chrome tungsten titanium buff rutile in environmentally relevant test medium at pH 6 and 8 was determined after 1, 7 and 28 days at a loading of 1 mg/L according to the OECD Series on Testing and Assessment 29: Guidance document on transformation/dissolution of metals and metal compounds in aqueous media ENV/JM/MONO(2001)9. The transformed/dissolved amount of the test item was quantified by assessing the elemental chromium, tungsten and titanium concentrations.

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Ti

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other:

Remarks:

conc. of all replicates < LOD (0.25 µg/L)

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 0.25 µg/L

Element analysed:

Cr

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOD (0.25 µg/L)

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Type of test:

screening transformation/dissolution test - sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

24 h

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 6, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Key result

Type of test:

full transformation/dissolution test - metals and sparingly soluble metal compounds

Mean dissolved conc.:

< 1 µg/L

Element analysed:

W

Loading of aqueous phase:

1 mg/L

Incubation duration:

28 d

Test conditions:

pH 8, 0.2 µm filtration

Remarks on result:

other: conc. of all replicates < LOQ (1 µg/L)

Details on results:

Ti, W and Cr concentrations of 0.2 µm filtered samples in the 28-d test at pH 6 and 8 at approx. 22°C were below the respective LODs/LOQs for all sampled timepoints (0h, 2h, 6h, 24h, 4d, 7d, 14d, 21d, 28d, see below)

Test parameters and method validation:

Temperature, solution pH, oxygen concentrations:

Mean temperature as recorded by a data logger (Testo 174-T) was 22.1 ± 0.2 °C during the 28 days full test for test solutions at pH 6 and pH 8 and recovery tests.

Solution pH remained in the respective target pH range from pH 5.93 - 6.07 (target pH 6) and from pH 7.92 – 8.02 (target pH 8) during the course of the test (0h – 28d).

Oxygen levels of all test solutions were in the range recommended by the OECD Test Guidance 29 during the test (> 70 % of oxygen saturation at 8.5 mg/L (70 % of 8.5 mg/L = 6 mg/L).

Analytical measurements:

Ti, W and Cr concentrations of 0.2 µm filtered samples in 28-d test at pH 6 and 8 at approx. 22°C were below the respective LODs/LOQs for all sampled timepoints (0h, 2h, 6h, 24h, 4d, 7d, 14d, 21d, 28d).

Cr/W/Ti limit of detection (LOD): 0.25 µg/L

Cr/W/Ti limit of quantification (LOQ): 1 µg/L

Within- and between-vessel variations in Ti, W and Cr concentrations: As all data are below the respective LOD/LOQ, no assessment of elemental within- and between-vessel variations was performed.

Method validation:

All elements (Ti, W, Cr) were proven linear within the injected analytical range at both pH 6 and 8 (Ti, Cr: 1 - 500.5 µg/L, W: 0.5 - 500.0 µg/L, correlation coefficients for all elements >0.99973)

Spiking experiments performed on all three elements (Ti, W, Cr) at pH 6 and 8 using reference material with known concentrations (10 µg/L, 100 µg/L) showed acceptable elemental recoveries ranging from 85.4 to 114.7 %.

Available certified reference materials:

Recovery of titanium reference material:

pH 6: 101% (certified: 25.1 ± 2.0 µg Ti /L; measured 25.5 µg/L)

pH 8: 102% (certified: 25.1 ± 2.0 µg Ti /L; measured 25.7 µg/L)

Recovery of chromium reference material:

pH 6: 97% (certified: 23.9 ± 1.7 µg Cr /L; measured 23.1 µg/L)

pH 8: 101% (certified: 23.9 ± 1.7µg Cr /L; measured 24.2 µg/L)

Conclusions:

The transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001) of chrome tungsten titanium buff rutile at a loading of 1 mg/L at pH 6 and 8 resulted after 1, 7 and 28 days in dissolved chromium, tungsten and titanium concentrations (0.2 µm fractions) that were below the limit of detection (Ti, Cr concentrations < LOD: 0.25 µg/L) and/or quantification (W concentrations < LOQ: 1 µg/L). Thus, the extent to which chrome tungsten titanium buff rutile can produce soluble available ionic and other metal-bearing species in aqueous media is limited.

Description of key information

Chrome tungsten titanium buff rutile (CAS number 68186-92-5) does not dissolve to any relevant extent under regular environmental conditions as determined in a transformation/dissolution test (OECD Series on Testing and Assessment Number 29, 2001). Measured dissolved chromium, tungsten and titanium concentrations (0.2 µm fraction) after 7 and 28 days at a loading of 1 mg/L at pH 6 and pH 8 were below the limit of detection (Cr, Ti: < 0.25 µg/L) or below the limit of quantification (W: < 1 µg/L). Thus, dissolution is not important for the environmental fate and behaviour of chrome tungsten titanium buff rutile in environmental compartments.