Autori: C.-M. Popescu, M.-C. Popescu, Gh. Singurel, C. Vasile, D. S. Argyropoulos, S. Willfor

Editorial: Appl. Spectrosc., 61 (11) , p.1168-1177, 2007.

Rezumat:

The main difficulties in wood and pulp analyses arise principally from
their numerous components with different chemical structures. Therefore,
the basic problem in a specific analytical procedure may be the selective
separation of the main carbohydrate-derived components from lignin due
to their chemical association and structural coexistence. The processing of
the wood determines some structural modification in its components
depending on the type of wood and the applied procedure. Fourier
transform infrared (FT-IR) spectrometry and X-ray diffraction have been
applied to analyze Eucalyptus g. wood chips and unbleached and chloritebleached
pulp. The differences between samples have been established by
examination of the spectra of the fractions obtained by successive
extraction (acetone extractives, acetone free extractive samples, hemicelluloses,
and lignins) by evaluating the derivative spectra, band deconvolution,
etc. The energy and the hydrogen bonding distance have been
evaluated. The relationship between spectral characteristics and sample
composition has been established, as well as the variation of the degree of
crystallinity after pulping and bleaching. The integral absorption and
lignin/carbohydrate ratios calculated from FT-IR spectra of the IR bands
assigned to different bending or stretching in lignin groups are stronger in
the spectrum of eucalyptus chips than those from brown stock (BS) pulp
spectra because of the smaller total amount of lignin in the latter. FT-IR
spectra clearly show that after chlorite bleaching the structure of the
wood components is partially modified or removed. Along with FT-IR
data, the X-ray results confirmed the low content of lignin in the pulp
samples by increasing the calculated values of the crystalline parameters.
It was concluded that FT-IR spectroscopy can be used as a quick method to differentiate Eucalyptus globulus samples.

Cuvinte cheie: Wood components; Fourier transform infrared spectroscopy; FT-IR spectroscopy; X-ray diffraction; XRDS