Preparation and certification of a reference material for the total mercury and methylmercury mass fractions in fish

Abstract

Certified reference materials (CRMs) play an important role in tracing results to the International System of Units through an unbroken chain of comparisons. Demand for new certified reference materials is steadily increasing in all areas. In Brazil, the demand for CRMs exceeds their availability by far, and the needs of the scientific community are not met. Food production is one area where CRMs are required, and they play an important role for export and local products. This paper describes the preparation and certification of a reference material for the content of mercury and methylmercury in fish samples. The material selection, preparation, homogeneity and stability studies, and characterization are described. Certification was performed by flow injection analysis–cold vapor atomic absorption spectrometry (FIA–CV-AAS) and isotope dilution–inductively coupled plasma mass spectrometry (ID–ICP-MS), which is a primary method. The standards ISO 30 (ABNT 30–34) and ISO Guide 35 were used as a basis for the preparation and characterization of the material. The material was certified for the mass fractions of total mercury w(total Hg) = (0.271 ± 0.059) lg g-1 and methylmercury w(MeHg) = (0.245 ± 0.053) lg g-1.