Dirhodium trioxide

Additional toxicological data

Administrative data

Endpoint:

additional toxicological information

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: study performed according to OECD Principles of Good Laboratory Practice, follows a standard operating procedure (Eurometaux (2016), available as an unpublished report, reliable without restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: SOP prepared by Eurometaux (2016); Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux Brussels, July 2016).

Principles of method if other than guideline:

Bio-elution refers to the in vitro extraction methods used to measure the degree to which a substance (e.g., metal or mineral ion) is dissolved in artificial biological fluids. Simulated biological fluids represent relevant exposure routes. The resulting value is the “bio-accessibility”, and is defined as the “fraction of a substance that is soluble under physiological conditions and therefore potentially available for absorption into systemic circulation”.
The objective of this study was to obtain knowledge about the bio-elution characteristics of the test item in simulated gastric fluid.
This study has been conducted according to the recommended Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux, July 2016) which is based on ASTM D5517-07: Standard Test method for determining the extractability of metals from art materials - ASTM, 2007 (American Society for Testing and Materials). The extent of dissolution of the test item was tested in a simulated gastric fluid at 37 °C and pH 1.5 for 2 hours (0.2 g/L loading) at an agitation speed of 100 revolutions per minute (rpm) for 1 hour followed by 1 hour of settling (without shaking). The bio-elution endpoints were based on the dissolved rhodium (Rh) concentrations obtained after 2 hours of extraction.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Dirhodium trioxide

EC Number:

234-846-9

EC Name:

Dirhodium trioxide

Cas Number:

12036-35-0

Molecular formula:

Rh2O3

IUPAC Name:

Rhodium(III)oxide

Details on test material:

Dirhodium trisoxide

Specific details on test material used for the study:

purity: 81.1 % Rh content corresponding to 99.91% Rh2O3
d10 4µm, d50 17 µm, d90 62 µm
SSA (N-BET) 0.25 m2/g
d=8.2 g/m³

Results and discussion

Any other information on results incl. tables

The temperature of the test solutions at the sampling point was between 36.9 °C and 37.0 °C, which was in line with the test conditions of 37 °C ± 1 °C.

The measured pH of the test medium at the start of the test was 1.50, i.e. within the specifications of pH 1.5 ± 0.1. The pH measured in the additional test item vessel at the start of the test was 1.50 i.e. within the specifications of pH 1.5 ± 0.1. At the 2 hours sampling point of the test, the pH in the blank control vessels and the test vessels was between 1.49 and 1.50.

The data of the dissolved rhodium concentrations in the test samples, are presented belw:

Dirhodium trioxide, 0.2 g/L (=0.05 m²/L surface loading), 2h gastric, pH 1.5
Rhodium	x(avg) +/- s(between)	CV
dissolution	<0.5 µg/L	-
absolute Rh release	<2.5 µg/g	-
% of total available Rh eluted	<0.00031%
Rh release/surface	<0.01 mg/m²

The blank control vessels during the test showed no concentrations above the reporting limit of rhodium (i.e. 0.5 μg/L Rh).

The following observations could be made in the test vessels with a loading of 0.2 g/L dirhodium trioxide:

Remaining test item could be observed on the filter and in the Erlenmeyer flasks at the end of the experiment. The test solution remained colourless.

 An average dissolved rhodium concentration below the reporting limit of 0.5 μg/L Rh (or <2.5 μg/g test item) was measured after 2 hours of exposure to the simulated gastric fluid (pH 1.5).

Based on the specific surface area of Dirhodium trioxide (0.25 m²/g test item) a rhodium release per surface of <0.010 mg/m² was calculated.

Based on the rhodium content of the test item (i.e. 81.1 %) and the average dissolved rhodium concentration, a rhodium release of <0.00031 % could be calculated at the 2 hours endpoint.

Applicant's summary and conclusion

Conclusions:

During this study on Dirhodium trioxide at a loading of 0.2 g/L in simulated gastric fluid (pH 1.5), it was shown that for rhodium an average value of <0.5 μg/L Rh (i.e. reporting limit; N = 3) was found after 2 hours of extraction, corresponding with a rhodium release of <0.00031 % (or <0.010 mg/m²).

Executive summary:

A study to estimate bioelution characteristics has been conducted according to the recommended Standard Operating Procedure (SOP) for Bioelution Testing of Metals, Inorganic Metal Compounds, and Metal-Containing Complex Materials: Simulated Gastric Fluid (Eurometaux, July 2016) which is based on ASTM D5517-07: Standard Test method for determining the extractability of metals from art materials - ASTM, 2007 (American Society for Testing and Materials). Bio-elution refers to the in vitro extraction methods used to measure the degree to which a substance (e.g., metal or mineral ion) is dissolved in artificial biological fluids. Simulated biological fluids represent relevant exposure routes. The resulting value is the “bio-accessibility”, and is defined as the “fraction of a substance that is soluble under physiological conditions and therefore potentially available for absorption into systemic circulation”.

The extent of dissolution of dirhodium trioxide was tested in a simulated gastric fluid at 37 °C and pH 1.5 for 2 hours (0.2 g/L loading) at an agitation speed of 100 revolutions per minute (rpm) for 1 hour followed by 1 hour of settling (without shaking). The bio-elution endpoints were based on the dissolved rhodium (Rh) concentrations obtained after 2 hours of extraction.

In the blank corrected test item vessels with a loading of 0.2 g/L Dirhodium trioxide, the following average dissolved rhodium concentration of <0.5 μg/L Rh (i.e. the validated reporting limit), was measured after 2 hours of exposure to the simulated gastric fluid (pH 1.5).

Based on the specific surface area of Dirhodium trioxide (i.e. 0.25 m²/g), this corresponds with a rhodium release per surface of <0.010 mg/m².

Based on the rhodium content (i.e. 81.1 %) in the test item and the average dissolved rhodium concentrations in the test solutions, a rhodium release of <0.00031 % could be calculated at the 2 hours endpoint.