Abstract
The importance of Brazilian bioethanol as biofuel has been increasing significantly. Its origin from renewable sugar cane is able to reduce carbon in the atmosphere and is one of the factors that contribute for reducing global warming. Because of the difficulty in measuring pH in nonaqueous solutions, Inmetro, the Brazilian Metrology Institute, has focused its attention on the needs for accurate and reliable pH measurements, as part of its work in developing and producing certified reference material (CRM) of bioethanol. This paper aims to present the studies of pH measurement in CRM of bioethanol from sugar cane (approximately 99.6 % ethanol content) using two commercial pH electrodes with different internal filling electrolytic solutions. One electrode, containing potassium chloride (KCl), was specified in the American standard, ASTM D6423, and the other one, containing lithium chloride (LiCl), was specified in the Brazilian standard, ABNT NBR 10891, and European standard EN 15490. These studies have shown that there was a significant difference among the pH values (more than 1.0 pH unit) measured by the different electrodes related to its internal filling solution. The results have shown that a harmonization of the standardization on the pH measurement is needed in order to make possible its use and application as analytical parameter.
