Primary standards for challenging elements

Millions of chemical analyses for different elements are performed every year in Europe. They enable accurate measurements for directives such as the In vitro diagnostic devices directive for laboratory medicine (IVD) or the EU Water Framework Directive (WFD) for environmental protection, as well as general requirements of international standards (e.g. ISO/IEC 17025). However, only a few pure single element solution standards with fully demonstrated SI traceability exist. Extending this number, and especially determining the standardisation methods for challenging elements, will increase comparability of chemical measurement results in both traditional and emerging product applications.

The project Primary standards for challenging elements (ELEMENTS) developed procedures and methods for realising SI traceable solution standards for four industrially important elements with potential for extending standard solution production to other chemically similar elements.

The project:

• Developed methods for preparing high purity samples of magnesium, zinc and aluminium in both solid and liquid forms with well characterised impurities and low uncertainties.
• Developed new reference materials for magnesium and for molybdenum containing well characterised ratios of different isotopes and used these for the calibration of mass spectroscopy instruments for chemical analyses.
• Demonstrated for the first time the comparability of results from advanced mass spectroscopy and more traditional isotope fractionation - techniques important for determining the quantity of specific isotopes present in samples containing mixes of isotopes of a single element.
• Developed methods for complete and loss-free digestion of virtually inert refractory elements molybdenum and rhodium enabling the preparation of primary elemental solutions.

This EMRP project increased the number of existing well characterised and SI traceable high-purity elemental solution standards. As a collaboration between eight European National Measurement Institutes and Designated Institutes, the project was able to pool expertise and resources to achieve more than any individual organisation on its own.

Although this project addressed SI traceability for only four key industrial elements, the solution preparation methods and improved rigour in isotopic sample evaluation will apply to many related elements in the periodic table. The new high purity solution standards for key industrial metals are now giving SI traceability across many of the millions of chemical analyses performed each year and contributing to the founding of a robust chemical measurement system that is fundamental for innovation in science and technology.