IAEA-413

​The IAEA-413 Algae reference material was prepared by the IAEA Terrestrial Environment Laboratory in Austria in co-operation with the Institute of Microbiology, Academy of Sciences of the Czech Republic in Trebon.

The IAEA-413 algae material (type: Chlorella Boehm) was produced under standard outdoor culture conditions. The bulk algae material and the sealed bottles were treated with gamma ray irradiation with a total dose of 25 kGy using a Co-60 source to improve long-term stability of the material by reducing microbial action.

* Uncertainty is expressed as a Mixture model median based standard deviation S(MM-median) at 95 % confidence level [1].
**number of accepted laboratory means which were used to calculate the reference values.

The reference and information values of all elements were established on the basis of a robust approach proposed by David L. Duewer and the Mixture Model Median (MM-median) of the analytical results reported by the expert laboratories. The MM-median is a direct analogue of the median. It is the location which divides the Mixture Model Probability Density Function (MMPDF) into two sections of equal area. To estimate the standard uncertainty associated with the property value the MM-median based Standard Deviation S(MM-median) was calculated from the span of the central 50% of the MMPDF density. The uncertainty related to long- and short-term stability was not considered. The property values assigned to the algae IAEA-413 reference material are element mass fractions, expressed in the derived SI unit mg/kg. The utmost care was taken regarding the metrological traceability of the property values assigned to this reference material already at the planning phase and during the entire characterization process. Laboratories participating in the characterization campaign have been requested to carefully choose the calibrants and to provide the IAEA with all related information, including certificates. However, the selection of measurement methods and measurement procedures, as well as respective calibrants, was based on a decision of the participating laboratory. A consequence of the use of different calibrants, is the fact that the metrological chain(s) for each of the assigned quantity values respectively (combined from number of results), cannot not easily be described. Therefore, the assigned property values – the element mass fractions – although expressed in the derived SI unit, are not intended for calibration purposes, and the reference material as such is not to be used as a calibrant. Further details on the characterization and calculation of property and uncertainty values can be found in the report IAEA/AQ/14, ‘Reference material IAEA-413: Major, minor and trace elements in algae’.