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A green method for determination of acid number of biodiesel

A simple green method for the determination of the acid number of biodiesel is described. The sample is dissolved in a 1:1 v/v ethanol:water mixture, avoiding the use of the usual toluene:isopropanol:water mixture (1:0.95:0.5 v/v/v). The titration is performed with a 0.02 mol L-1 NaOH solution in water. The method was compared with that of ABNT NBR 14448, which is similar to ASTM D 664 and to EN 14104. A statistical comparison using the student's t test and the Snedecor F test showed that the proposed method offers equivalent results to ABNT NBR 14448, with better precision.

biodiesel; acid number; green method; titration; potentiometry


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