Second- and third-generation feedstocks,
combined with first-generation
feedstocks, have been showing a tendency to meet the supply and quality
standards of biodiesel, a less polluting renewable energy source that
has been gaining prominence year after year. The objective of the
study was to quantify the weight proportion (%) that each biodiesel
contributed to the composition of the blend, in addition to the presence
of the adulterant soybean oil. Fourier-transform infrared spectroscopy
combined with chemometric techniques allowed distinguishing between
feedstocks of the animal and vegetable origin and adulterants and
determining their ratios in 45 blends. Multivariate control charts
based on the net analyte signal allowed obtaining most data on biodiesel
from beef tallow and lard, whereas the interference chart was used
for matrix variability. Partial least squares discriminant analysis
(PLS-DA) was applied to the same dataset, and the coefficient of determination
was 0.9999 for the calibration and prediction sets, proving to be
a robust method for the identification of B100 biodiesel blends from
different feedstocks and adulterants. PLS was used as a qualitative
and quantitative tool, showing optimal correlation between calibration
and prediction, with R
cv
2 =
0.9999 and R
p
2 = 0.9999, and
low root-mean-square error of cross-validation and root-mean-square
error of prediction values. Orthogonal signal correction was employed
for data processing in the PLS-DA and PLS models, rendering them more
cohesive and eliminating the variability of the dataset that is orthogonal
to the parameter of interest. The full spectral range and only one
latent variable were used. PLS-DA and PLS models proved to be 100%
reliable for the identification and quantification of adulterants
in biodiesel and biodiesel blends.