caa a22 4500 605465789 CHVBK 20210128100304.0 cr unu---uuuuu 210128e20150601xx s 000 0 eng 10.1007/s00769-015-1133-4 doi (NATIONALLICENCE)springer-10.1007/s00769-015-1133-4 Treatment of bimodality in proficiency test of pH in bioethanol matrix [Elektronische Daten] [Gabriel Sarmanho, Paulo Borges, Isabel Fraga, Luiz Leal] The pH value in bioethanol is a quality control parameter related to its acidity and to the corrosiveness of vehicle engines when it is used as fuel. In order to verify the comparability and reliability of the measurement of pH in bioethanol matrix among some experienced chemical laboratories, reference material of bioethanol developed by Inmetro—the Brazilian National Metrology Institute—was used in a proficiency testing (PT) scheme. There was a difference of more than one unit in the value of the pH measured due to the type of internal filling electrolytic solutions (potassium chloride, KCl, or lithium chloride, LiCl) from the commercial pH combination electrodes used by the participant laboratories. Therefore, bimodal distribution has occurred from the data of this PT scheme. This work aimed to present the possibilities that a PT scheme provider can use to overcome the bimodality problem. Data from the PT of pH in bioethanol were treated by two different statistical approaches: kernel density model and the mixture of distributions. Application of these statistical treatments improved the initial diagnoses of PT provider, by solving bimodality problem and contributing for a better performance evaluation in measuring pH of bioethanol. Springer-Verlag Berlin Heidelberg, 2015 Bioethanol nationallicence pH nationallicence Proficiency test nationallicence Multimodality nationallicence Kernel density nationallicence Mixture of densities nationallicence Sarmanho Gabriel Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut Borges Paulo Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut Fraga Isabel Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut Leal Luiz Corporate Management Division (Dgcor), National Institute of Metrology, Quality and Technology (Inmetro), R. Santa Alexandrina, 416, 20261-232, Rio Comprido, Rio de Janeiro, Brazil aut Accreditation and Quality Assurance Springer Berlin Heidelberg 20/3(2015-06-01), 179-187 0949-1775 20:3<179 2015 20 769 https://doi.org/10.1007/s00769-015-1133-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00769-015-1133-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sarmanho Gabriel Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut NATIONALLICENCE 700 1- Borges Paulo Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut NATIONALLICENCE 700 1- Fraga Isabel Chemical Metrology Division (Dquim), National Institute of Metrology, Quality and Technology (Inmetro), Av. Nossa Senhora das Graças, 50, 25250-020, Xerém, Rio de Janeiro, Brazil aut NATIONALLICENCE 700 1- Leal Luiz Corporate Management Division (Dgcor), National Institute of Metrology, Quality and Technology (Inmetro), R. Santa Alexandrina, 416, 20261-232, Rio Comprido, Rio de Janeiro, Brazil aut NATIONALLICENCE 773 0- Accreditation and Quality Assurance Springer Berlin Heidelberg 20/3(2015-06-01), 179-187 0949-1775 20:3<179 2015 20 769