A simple and green analytical method for acid number analysis of biodiesel and biodiesel blends based on potentiometric technique

Acid number is an important quality parameter for biodiesel and biodiesel blends and has been included in various quality standards including ASTM D 6751 and EN 14214. In this paper, a new simple and green potentiometric method based on green chemistry approaches has been developed to determine the acid number of biodiesel and biodiesel blends. This new method uses a reduced amount of titration solvent and recommends the use of a small sample size instead of large sample size as stated in the ASTM reference method D664. A time-efficient electrode cleaning procedure has been developed which completely eliminates the use of toxic solvents for cleaning the electrodes. This proposed green method significantly reduced the maximum % error from 101% to only −18% and repeatability was decreased from 290% to 100% when compared to ASTM D 664 method using the sample size of 2 g. This proposed green analytical method could be used for the determination of acid number of biodiesel and biodiesel blends in R&D as well as in industrial quality control laboratories as a simple, time-efficient, cost effective, and environmentally friendly method for acid number determination.