A new method for determining the acid number of biodiesel based on coulometric titration

TALANTA

卷:97

Article

Gonzaga, Fabiano Barbieri¹  Sobral, Sidney Pereira¹ 

[1] Natl Inst Metrol Qual & Technol, Chem Metrol Div, BR-25250020 Duque De Caxias, RJ, Brazil

关键词: Biodiesel;    Acid number;    Acidity;    Coulometric titration;   

DOI  :  10.1016/j.talanta.2012.04.017

来源: Elsevier

【 摘 要 】

A new method is proposed for determining the acid number (AN) of biodiesel using coulometric titration with potentiometric detection, basically employing a potentiostat/galvanostat and an electrochemical cell containing a platinum electrode, a silver electrode, and a combination pH electrode. The method involves a sequential application of a constant current between the platinum (cathode) and silver (anode) electrodes, followed by measuring the potential of the combination pH electrode, using an isopropanol/water mixture as solvent and LiCl as the supporting electrolyte. A preliminary evaluation of the new method, using acetic acid for doping a biodiesel sample, showed an average recovery of 100.1%. Compared to a volumetric titration-based method for determining the AN of several biodiesel samples (ranging from about 0.18 to 0.95 mg g(-1)), the new method produced statistically similar results with better repeatability. Compared to other works reported in the literature, the new method presented an average repeatability up to 3.2 times better and employed a sample size up to 20 times smaller. (C) 2012 Elsevier B.V. All rights reserved.

【 授权许可】

Free