Characterization of 25 tropical hardwoods with Fourier transform infrared, ultraviolet resonance Raman, and ¹³C‐NMR cross‐polarization/magic‐angle spinning spectroscopy

Abstract

Twenty-five tropical hardwoods from Ghana were examined with Fourier transform infrared (FTIR), ultraviolet resonance Raman (UVRR), and 13 C-NMR crosspolarization/magic-angle spinning spectroscopy. FTIR and UVRR spectral data were subjected to principal component analysis, whereas four selected samples exhibiting large structural and compositional variation were investigated in more detail by NMR spectroscopy. The acetyl bromide lignin and ␣-cellulose contents of the samples and the amount of acetone-soluble substances were also determined. The most prominent principal components of the FTIR spectral model separated samples mainly due to the variations in lignin structures and carbohydrate contents and the amount and type of carbonyl structures, whereas UVRR spectral data distinguished between various aromatic and other unsaturated structures. The presence of condensed lignin/tannin-type structures were detected from UVRR and FTIR loading line plots of the minor principal components. Condensed tannins were also observed in the dipolar dephasing NMR spectra. Furthermore, the NMR results showed variations in the amount of crystalline cellulose and hemicelluloses and in the syringyl/guaiacyl proportions in lignin. Both NMR and FTIR data suggest that in most cases, a higher amount of guaiacyl units correlated with higher levels of acetyl bromide lignin and better bioresistance of the samples.

FTIR spectroscopy, chemical and histochemical characterisation of wood and lignin of five tropical timber wood species of the family of Dipterocarpaceae

“…Only, H. plagata contained significantly less lignin (-16%) than the other species (Table 1). All lignin concentrations reported here are at the lower end of those reported in other investigations for tropical tree species (Fengel et al 1983;Saka 2001;Pastore et al 2004;Nuopponen et al 2006;Jahan and Mun 2007;Santana and Okino 2007). The low lignin concentration of H. plagata was surprising since this species is reported to be among the most durable dipterocarps (Newman et al 1996) pointing to other factors as determinants of durability.…”

“…The low lignin concentration of H. plagata was surprising since this species is reported to be among the most durable dipterocarps (Newman et al 1996) pointing to other factors as determinants of durability. Durability in tropical hardwoods is affected by the combination of wood density and the content and composition of lignin and extractives (Onuorach 2000;Nuopponen et al 2006). It must, therefore, be considered that the five species of our study differ in their contents of extractives and wood densities.…”

Raman Spectroscopic Characterization of Wood and Pulp Fibers

“…Additionally, it was reported that, although present in significant quantity (20-30%), very few hemicellulose Raman contributions were detected. In more recent work [19], ultraviolet resonance Raman (UVRR) in conjunction with principal component analysis has been used to characterize woods, and using this approach, it was possible to distinguish between various aromatic and other unsaturated structures in wood.…”

In-SituObservation of Tryptophan in Larval Cocoon Silk of the HornetVespa simillima xanthopteraCameron by Ultraviolet Resonance Raman Spectroscopy

“…We expect that UVRR spectroscopy will be able to provide information on not only the presence of a Trp residue, but also on the structure and environment of Trp in the native state in the cocoon, because the UVRR spectrum is sensitive to the structure and environment in relation to the side chains of aromatic compounds in the solid state. 7) Moreover, the UVRR spectrum reflects the conformational properties of Trp in proteins.…”

“…6) Moreover, recent developments in UVRR have enabled the detection of solid materials. 7) However, this technique has never been applied to the structural analysis of fibrous proteins in the solid state, to our knowledge.…”