Examples of coulometric titration curves obtained for some of
the biodiesel samples analyzed are shown in Fig. 4.
As can be observed, the titration curves showed good resolution and amplitude around the inflection region, allowing visual differentiation of the samples according to their acidity and precise determination of the AN.
The average AN results obtained using the
coulometric and the volumetric methods, including the relative
standard deviations (RSD) of replicates, are shown in Table 2