FTIR spectroscopy. FTIR spectra of the oil samples were
acquired on a Bruker Vector 33 spectrometer interfaced with
a personal computer operating under Windows NT. All spectra
were recorded from 4000 to 500 cm−1 with a resolution
better than 4 cm−1, co-adding 32 interferograms, with an accuracy
in the frequency data of better than 0.01 cm−1.