Determination of Eucalyptus spp lignin S/G ratio: a comparison between methods

Abstract

The syringyl/guaiacyl ratio was determined for six different Eucalyptus spp. wood clones cultivated in four regions in Brazil. The determinants were made by pyrolysis–gas chromatography–mass spectrome- try (Py–GC–MS) and the results were compared with those obtained by alkaline nitrobenzene oxidation method. The S/G ratios were obtained considering all the identified lignin derivatives in the pyrograms and also using two groups of markers. The first group of markers consisted of guaiacol, 4-methylguaiacol, 4-vinylguaiacol, trans-isoeugenol, syringol, 4-methylsyringol, 4-vinylsyringol and trans-4-propenylsyrin- gol compounds as markers. The second group included guaiacol, 4-methylguaiacol, 4-vinylguaiacol, van- illin, 4-ethylsyringol, 4-vinylsyringol, syringaldehyde, syringylacetone and trans-4-propenylsyringol. It was observed from the statistical analysis that the values of S/G obtained by Py–GC–MS using the two groups of markers did not differ significantly from those obtained by nitrobenzene oxidation method.