Determinação da relação siringila/guaiacila em ligninas de Eucalyptus spp. por pirólise associada à cromatografia gasosa e à espectrometria de massas

• Autor(a) principal: Marcelo, Cristiana Resende
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2182
• topic: Relação siringila/guaiacila; Lignina; Pirólise; Cromatografia à gás; Espectrometria de massa; Syringyl/guaiacyl ratio; Lignin; Pyrolysis; Gas chromatography; Mass spectrometry; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ANALITICA

Lignin is one of the main components of the wood together with cellulose and hemicellulose. Its structure is quite complex being built up by p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units. Some studies show that the lignin structural composition may affect the pulping process. Thus, some analyses of the wood of six species of eucalyptus were done by Py-GC-MS. The samples were pyrolysed to 550 °C and 42 composts were identified from which 11 were derived from carbohydrates and 31 from lignin. The syringyl/guaiacyl (S/G) ratio was calculated based upon the area values of the recorded signals and compared to the result obtained by the alkaline nitrobenzene oxidation method. The estimative values through pyrolysis were not satisfactory for all the species, principally for Eucalyptus globulus. However, there were some improvements in the results when the guaiacol, 4-methylguaiacol, 4-vinylguaiacol, vanillin, 4-ethylsyringol, 4- vinylsyringol, homosyringaldehyde, acetosyringone and syringylacetone composts were used as lignin markers, except for E. globulus. For this particular species, it was necessary to add one more marker, the trans-4- propenylsyringol. By comparing the variability of S/G ratio in the eucalyptus species, the one which had the lowest value was E. urograndis (2,0), almost half the value found for E. globulus (4,3). The proposed methodology employing the lignin markers was useful for the establishment of S/G ratio in eucalyptus wood by Py-GC-MS for the quickness of the analysis, the consumption of small amounts of the sample and the possibility of working with the material in situ.