CTO

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:

August to September 2018

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

Version / remarks:

2001

Deviations:

yes

Remarks:

One deviation from guidelines was reported. Considered uncritical.

GLP compliance:

yes (incl. QA statement)

Type of method:

flask method

Specific details on test material used for the study:

Batch no.: B0345
Purity: >99%
Homogeneity: homogeneous

Type of test:

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

Mean dissolved conc.:

0.307 mg/L

Element analysed:

Tungsten (W)

Loading of aqueous phase:

1 mg/L

Incubation duration:

7 d

Test conditions:

at 20.0 – 20.9 °C

Remarks on result:

other: Loading rate is nominal

Type of test:

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

Mean dissolved conc.:

2.533 mg/L

Element analysed:

Tungsten (W)

Loading of aqueous phase:

10 mg/L

Incubation duration:

7 d

Test conditions:

at 20.0 – 20.9 °C

Remarks on result:

other: Loading rate is nominal

Type of test:

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

Mean dissolved conc.:

17.754 mg/L

Element analysed:

Tungsten (W)

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

at 20.0 – 20.9 °C

Remarks on result:

other: Loading rate is nominal

Type of test:

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

Mean dissolved conc.:

5.697 mg/L

Element analysed:

Cesium (Cs)

Loading of aqueous phase:

100 mg/L

Incubation duration:

7 d

Test conditions:

at 20.0 – 20.9 °C

Remarks on result:

other: Loading rate is nominal

Details on results:

For the calibration, the ranges of 50 – 2000 μg/L Tungsten (W) and 2000 – 10000 μg/L Cesium (Cs) were used. The reproducibility test was performed with 100 mg/L test item (nominal) in pH 8.5 buffer solution over a period of 24 hours as the highest concentration of W and Cs was measured at pH 8.5 during the screening test in the validation study. Five vessels were prepared; each flask was measured in triplicate. A within-vessel variation of max. 10% and a between-vessel variation of max. 20% is demanded. These conditions were fulfilled. Therefore, for the main test three flasks per concentration with double determination were used.

The main test was performed with three different concentrations of the test item (nominal loads of 1, 10 and 100 mg/L, three replicates each) over a period of 7 days with samplings after 2 h, 6 h, 1 d, 4 d and 7 d. Two flasks were prepared as blanks without addition of test item. No linear dependency of measured concentrations vs. time was observed. Furthermore, no equilibrium was observed during the test. As no linear dependency of measured concentrations vs. time was observed, the first order model was used for the determination of kinetic and the first order constant was calculated for W. The Cs values lay above the LOQ in the flasks 9 – 11 on days 4 and 7 only. Therefore, the determination of kinetic was not possible for Cs. Both conditions RSD < 10 % (within-vessel) and < 20 % (between-vessel) were fulfilled for W and the condition < 20 % (between-vessel) for Cs in all flasks at each sampling point. The condition RSD < 10 % (within-vessel) was not fulfilled for Cs in the flask 9 (4 d) and in the flasks 10 and 11 (7 d). This was considered as uncritical as the between vessel variation was far below 20 % for Cs. The mass balance in flasks 9 – 11 lay in the range of 100 ± 4 %. The values in the flasks 7– 8 were higher than 200 % due to an imprecise determination of low concentration 10 mg/L. No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.

Four deviations for the study plan were noted. These were all considered uncritical. One deviation from the guideline was reported. This was also considered uncritical. No observations arousing doubts concerning the accuracy of the results and the validity of the study were made.

Conclusions:

In this study, the maximum concentration of total dissolved metals W and Cs was determined in order to identify compounds of Cesium Tungsten Oxide which undergo either dissolution or rapid transformation. The main test was performed with three different concentrations of the test item (nominal loads 1, 10 and 100 mg/L, three replicates each) over a period of 7 days. For the determination of kinetic, the first order model was used, and the first order constant was calculated for W. The Cs values lay above the LOQ on days 4 and 7 only. Therefore, the determination of kinetic was not possible for Cs. The following concentrations of W and Cs at 20.0 – 20.9 °C were reported:
1 mg/L nominal: 0.307 mg/L W
10 mg/L nominal: 2.533 mg/L W
100 mg/L nominal: 17.754 mg/L W; 5.697 mg/L Cs

Executive summary:

In this study, the maximum concentration of total dissolved metals W and Cs was determined in order to identify compounds of Cesium Tungsten Oxide which undergo either dissolution or rapid transformation. The main test was performed with three different concentrations of the test item (nominal loads 1, 10 and 100 mg/L, three replicates each) over a period of 7 days. For the determination of kinetic, the first order model was used, and the first order constant was calculated for W. The Cs values lay above the LOQ on days 4 and 7 only. Therefore, the determination of kinetic was not possible for Cs. The following concentrations of W and Cs at 20.0 – 20.9 °C were reported:

1 mg/L nominal: 0.307 mg/L W

10 mg/L nominal: 2.533 mg/L W

100 mg/L nominal: 17.754 mg/L W; 5.697 mg/L Cs

Description of key information

The transformation/dissolution of the sparingly soluble Cesium Tungsten Oxide in aqueous media was determined according to OECD guidance document 29. Maximum concentrations of total dissolved Cesium (Cs) and Tungsten (W) were measured per ICP-OES in aqueous media. The main test was performed with three different concentrations of the test item (nominal loads 1, 10 and 100 mg/L, three replicates each) over a period of 7 days. For the determination of kinetic, the first order model was used, and the first order constant was calculated for W. The Cs values lay above the LOQ on days 4 and 7 only. Therefore, the determination of kinetic was not possible for Cs. The following concentrations of W and Cs at 20.0 – 20.9 °C were reported:

1 mg/L nominal: 0.307 mg/L W

10 mg/L nominal: 2.533 mg/L W

100 mg/L nominal: 17.754 mg/L W; 5.697 mg/L Cs