Before chemometric analysis, the use of Standard Normal Variate
(SNV) (Barnes, Dhanoa, & Lister, 1989), alone or coupled with
first derivative, was tested as a pre-treatment. SNV gives the
practical result of removing scatter effects from spectral data
(Zhang et al., 2009). The Savitzky-Golay method with third-order
smoothing polynomials through eleven points was used to compute
the first derivative of the spectra (Savitzky & Golay, 1964). The
use of SNV and first derivative was effective in eliminating unwanted
variations, like baseline shifts and drifts.