2.3. FT-IR spectroscopy and chemometric analysis
The FT-IR spectra of the three collections of samples were
obtained using a Golden Gate single reflection diamond ATR
system in a Bruker IFS-55 spectrometer. The spectra were
recorded at the absorbance mode from 4000 to 400 cmK1 (mid
infrared region) at the resolution of 8 cmK1. Five replicate
spectra (128 co-added scans) were collected for each sample.
The measured spectra were transferred via a JCAMP.DX
format into the data analysis software package for PCA and
each spectrum, within the 1200–800 cmK1 region, was SNV
(standard normal deviates) corrected. The PCA analysis could
allow the characterisation of the sample relationships (scores
plans or axis) and, at the same time, the recover of their subspectral
profiles (loadings).