International comparisons for coulometric determinations of dichromate used to develop certified reference material for oxidation-reduction titration

• Autor(a) principal: Borges,Paulo P.
• Data de Publicação: 2014
• Outros Autores: Silva Junior,Wiler B. da
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532014000600015
• topic: certified reference material; precise coulometric titration; potassium dichromate; comparability

Initially, for acquiring experience in determining the purity of the dichromate by coulometry, a bilateral comparison between the national metrology institutes (NMIs) from Brazil and Russia was carried out. Next, to evaluate the comparability of the measurement results among the NMIs that use high-precison constant-current coulometry for certifying reference materials (RMs) of pure compounds, National Institute of Metrology, Quality and Technology (Inmetro) participated in a key-comparison named CCQM-K96. Because of both comparisons, a batch of the RM of K2Cr2O7 was certified. This work aims to present the international comparison results, as well as the studies needed to develop a certified reference material (CRM) of K2Cr2O7 for redox titrations. In the certification of the batch, studies of homogeneity and characterization were considered. The K2Cr2O7 batch was certified in mass fraction of 99.974% ± 0.011%, for k = 2 and coverage probability of approximately 95%.