Organic , Vegetation
Certified values for mass fractions: platinum and trace elements
(based on dry mass)
* The certified values are given as total mass fractions of listed elements.
**The uncertainty is expressed as a combined standard uncertainty with a coverage factor k = 1 estimated in accordance with the JCGM 100:2008 Evaluation of measurement data — Guide to the expression of uncertainty in measurement and ISO Guide 35 'Reference materials - General and statistical principles for certification.
This material was thoroughly characterized by group of national metrological laboratories. The certified mass fractions are based on measurement results obtained from national metrological laboratories using validated methods with known accuracy and sufficiency traceability. ICP MS technique was mainly used by all laboratories and applied isotope dilution techniques wherever applicable. INAA technique was used by few laboratories for As, Cr measurements.
The certified values were derived as an Algorithm A as described in Annex C of ISO 13528. Mean and median were also calculated for comparison purposes. These values were compared with the calculated respective Algorithm A values and no significant difference was observed which ensures reliable estimation of assigned value.
The uncertainties associated with the reference values were calculated according to the JCGM 100:2008 Evaluation of measurement data - Guide to the expression of uncertainty in measurement and ISO Guide 35. The combined uncertainty of the certified values consists of uncertainty components associated with characterization (uchar), between bottle heterogeneity (ubb) and stability (ustab). These different contributions were combined to estimate the standard uncertainty.
The quantity values assigned to the certified reference material are mass fractions of specified elements, expressed in the derived SI unit mg kg−1. Values were derived from individual results reported by the metrological institutes through CCQM(BIPM) key comparison/pilot studies. Evidence on metrological traceability to the SI Units was provided for all results taken into account for the calculation of the assigned values.The details concerning the criteria for qualification as certified value may be found in the internal report NAEL/RM/002 ‘Certification of mass fractions of platinum and trace elements in CRM IAEA-450 (algae) sample’, Vienna, September 2015 (attached).