Preliminary Studies of a Certified Reference Material Candidate’s for Fluoride and Nitrate in Water

Maria Anita Scorsafava¹, Gisele Letícia Alves¹, Arlete de Souza¹, Camila de Oliveira Cardoso², and Carla Regianni Walter¹

1. Water and Packaging Center, Contaminant Center, Adolfo Lutz Institute, Brazil

2. Data Treatment Analysis Center, Reference Materials Cente, Adolfo Lutz Institute, Brazil

3. Center for Chemical and Bromatological Sciences, Adolfo Lutz Institute, Brazil

Abstract: The availability of reference materials is still incipient on account of their high demand and few products avaiable. This is observed especially in Brazil. Importing materials, on the other hand, has a high cost and long acquisition time. Therefore, we propose the development of a certified reference material candidate’s for fluoride and nitrate in water. We used the water supplied by the state of São Paulo's sanitation company SABESP (Companhia de Saneamento Básico do Estado de São Paulo) as the raw material, adding nitrate to obtain a concentration of 5 mg/L and maintaining the producer's concentration of fluoride. The sample was then homogenized and filtered through 0.45 m membranes directly into polyethylene bottles (250 mL each). After being filling in the bottles, the samples were subjected to gamma radiation with Cobalt 60 (25 kGy). The homogeneity and stability (short term) of the samples were evaluated using the UV-visible spectrophotometry and potentiometry methods for nitrate and fluoride analyses, respectively. The radiation led to a loss of 80% of the nitrate concentration. The studies conducted on homogeneity and short-term stability of the material indicated that the material was homogeneous and stable with respect to the concentration of fluoride ion, even when the material was subjected to high temperatures for 13 days; therefore, it can become a certified reference material.

Key words: public supply water, nitrate, fluoride, reference material, radiation