Characterisation and quantification of wood extractives and their impact on pitch.
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The aims of this study were to characterise and quantify wood extractives in E. grandis and E. nitens and determine the impact of wood extractives on pitch formation. Initially a comparison was made with individual solvent abilities to determine whether the polarity index plays a role in the amount of extracts being removed. After this different methods were used to determine the extractive amounts. These methods included hot water/ethanol-toluene, hot water/acetone and followed by acetone only. Analyses such as UV-Vis, acidolysis and HPLC were carried out to determine the presence of lignin and sugars in the extracts and sawdust respectively. Lastly GC and GC-MS was performed to characterise and quantify extractives present in the extracts from the different methods. The results showed that acetone is the preferred solvent as it removes higher amounts of extractives than ethanol-toluene. There is also a higher amount of extractives in E.grandis sawdust than in the E. nitens sawdust and pitch sample. There seems to be more fatty acids and sterols in the E. nitens sawdust sample extracted the using acetone (no hot water extraction) method while hydrocarbons are extracted more in E. grandis using the same method. It was found after GC-MS analysis that fatty acids tetradecanoic acid methyl ester and hexadecanoic acid methyl ester and hydrocarbon 1-Octadecene were common to both species. The common compounds in the pitch and sawdust of E. nitens are heptadecanoic, octadecanoic, tetradecanoic and tridecanoic acid methyl esters, gamma and beta sitosterol and Stigmasterol, 1-docosene and lastly 1-nonadecene hence these compounds are more likely to cause pitch. After analysis using UV analysis and acidolysis there was indication that there were lignin breakdown products present in the wood extracts, in minimal amounts. HPLC indicated no sugars present in the extracts. It is concluded that GC and GC-MS are the recommended analytical tools in characterising and quantifying wood extractives in E. grandis and E. nitens. All extractives in both species were quantified and identified using GC and GC-MS respectively.