By
Brazilian law, biodiesel has to satisfy certain quality requirements
and measurements established by standardized procedures, as is the
case for kinematic viscosity and density. In this respect, information
on the profile of methyl esters in biodiesel is very important because
they are directly related to both these parameters. The objective
of this study was to determine the profile of methyl esters present
in a biodiesel sample by electrospray ionization mass spectrometry
and evaluate its reliability in predicting their kinematic viscosity
and density. Two multivariate statistical models were used for this
purpose, the multiple multivariate linear regression (MMLR) and the
partial least square regression (PLSR). The input variables used in
the models were the relative intensities of the main methyl ester
peaks, and the models were compared by their predictive behavior.
Samples were randomly divided into two parts: 87% in the training
or calibration set, used for the estimation of MMLR and PLSR models,
and the remaining 13% in the test or validation set, which was used
to evaluate the predictive power of each model that was estimated.
Although the root mean squared error and R
2 for the MMLR model were slightly better than those of the PLSR model
(R
2
PLSR = 0.9232 and R
2
MMLR = 0.9908 for kinematic viscosity
and R
2
PLSR = 0.8721 and R
2
MMLR = 0.9415 for density), both
showed a similarity with respect to predicted values for the training
and validation sets, and thus for the performance statistics, attesting
to the quality of these models in predicting kinematic viscosity and
density. Furthermore, the prediction of kinematic viscosity showed
better performance compared to the density.