Potassium solution Certified Reference Material production at Inmetro

This paper presents the production of a potassium solution Certified Reference Material (CRM), MRC 8757.0001. The CRM was produced by the formulation method, using a high-purity potassium chloride (KCl) certified for purity at Inmetro, in compliance with ISO 17034, ISO 33405, and internal standards. High-Performance Inductively Coupled Plasma Optical Emission Spectrometry (HP-ICP-OES) was used to assess the homogeneity, short-term stability (at 50 °C), and long-term stability (between 20 °C and 25 °C) of the CRM. The certified potassium mass fraction, with all masses corrected for air buoyancy, was (1002 ± 11) mg/kg, considering k = 2.02, at a 95 % confidence level. With both the formulation method as a characterisation strategy and HP-ICP-OES for certification studies, we achieved a 47 % reduction of the combined uncertainty when compared to previous procedures at Inmetro. This CRM supports Inmetro’s objective to address the demand for metrological traceability of Brazilian organizations.