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 (RM) 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 aims 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.

翻译：生物乙醇中的pH值是与其酸度和作为燃料使用的汽车发动机腐蚀性有关的质量控制参数,生物乙醇中的pH值是生物乙醇矩阵中一些有经验的化学实验室对pH值测量的可比性和可靠性进行核查的参数,Inmetro-巴西国家计量研究所开发的生物乙醇参考材料(RM)用于熟练测试计划,由于参与实验室使用的商用pH混合电极(氯化石蜡、氯硅或锂氯化物、硅酸盐)的内填充电解液类型而测量的pH值有一个以上单位的差别,因此,双式分配产生于这一计划的数据,这项工作的目的是介绍PT计划提供者能够用来克服双式问题的可能性,生物乙醇中pH的PH值的PH值通过两种不同的统计方法处理:内核密度模型和分配混合物。应用这些统计处理改进了对PT提供者的初步诊断,方法是解决双式乙醇问题,促进生物乙醇的改进性能评估。