Biodiesel is a biodegradable fuel that consists of alkyl esters,
obtained from renewable sources, vegetal oil and animal fats
reacting with a short-chain of aliphatic alcohols (typically
methanol or ethanol) in the presence of a catalyst (reaction known
as transesterification).
An important property to use the biodiesel as fuel in diesel
engines is its oxidation stability because biodiesel can contain
unsaturated fatty acids, which are susceptible to oxidation, being
able to change into polymerized compounds, which can cause engine
problems such as blocked fuel filters.
Numerous analytical methods have been applied to determine
oxidation stability, European Union and Brazil use the same method
DIN EN 14112 - known as Rancimat method that consists in the sample
heating to 110°C where the products formed by the decomposition are
blown inside by a flow of air in to measurement cell with distilled
water. The time of induction is determined by the measure of the
conductivity being minimum limit to be approved according to the
Brazilian and European Union standard is 6 hours.
As alternative to this method it was developed a correlation
study of the obtained by the method DIN EN 14112 - Rancimat with
the method using UV-Vis in the wavelength of 550 nm getting R2 =
0,9767 indicate that the model fits better the data, shorter answer
response time, only one minute and small amount of sample and the
possibility of its reuse.