A novel method to produce homogeneous certified reference materials for neutron activation analysis
Scientists from the JRC, in collaboration with colleagues from the University of Leoben (Austria), the Atomic Centre Bariloche (Brazil) and Umicore (Belgium) developed a novel approach for the production of an Al-Au alloy certified reference material (CRM). This CRM is necessary for the quality assurance of results using neutron activation analysis for trace element determination which is applied for e.g. environmental monitoring.
Neutron activation analysis is a highly reliable method, that is used, amongst others, for environmental monitoring and monitoring of foodstuffs for toxic trace elements. While the method is very versatile and independent of sample preparation steps, it does require a certified reference material (CRM) to deliver reliable results. For more than 20 years, the most trusted CRMs have been produced by JRC-Institute for Reference Materials and Measurements (IRMM) and consist of an aluminium-gold alloy. These standards underpin the vast majority of all neutron activation analyses worldwide.
In a new approach for preparation of new Al-Au alloy CRMs, the a master batch of higher Au mass fraction is prepared which is then subsequently diluted to the final mass fraction and heat-treated to improve homogeneity. This process is more efficient than the levitation melting process used in the past, and delivered a material that was even more homogeneous than previous CRMs. The final material was converted into foils and wires and was characterized for its Au mass fraction in an intercomparison among 16 expert laboratories world-wide. The better homogeneity of the new CRM, combined with the stringent quality control and highly accurate methods used in the intercomparison resulted in an uncertainty of the certified value that is only about half as large as the one for previous CRMs. Therefore, this work of the JRC-IRMM allows neutron activation analysis laboratories to perform their monitoring tasks with even higher accuracy.