Purity assessment using the mass balance approach for inorganic in-house certified reference material production at Inmetro

Abstract

The production of Certified Reference Materials (CRMs) is one of the essential activities of the National Institute of Metrology, Quality and Technology (Inmetro) to ensure metrological traceability of inorganic elemental measurements in Brazil. This work presents a set of procedures for purity assessment and in-house certification of high-purity salts, implemented at the Laboratory of Inorganic Analysis, from the Chemical and Thermal Metrology Division at Inmetro. We developed and validated methodologies based on inductively coupled plasma mass spectrometry, energy-dispersive X-ray fluorescence spectrometry and inductively coupled plasma optical emission spectrometry measurements with standard addition calibration in order to determine the mass fraction of up to 71 elements considered as possible impurities. The purity of inorganic salts was determined using the mass balance approach with expanded measurement uncertainties smaller than a mass fraction of 0.007 %. All procedures were performed according to the ISO 17034:2016 standard. The CRMs will be used for the production and certification of single-element calibration solutions at Inmetro.