Pyrolysis/methylation: A method for structural elucidation of the chemical nature of aquatic humic substances

Pyrolysis has been used for the last ten years to study the chemical nature of humic substances. However, obtaining data is hampered by analytical limitations. One of these is that carboxylic acids other than fatty acids are not usually present amongst pyrolysis products. To overcome this problem, a novel method - pyrolysis/methylation - is applied. Simultaneous pyrolysis/derivatization with tetramethylammonium hydroxide protects the carboxyl groups by formation of methyl esters. At the same time, partial methylation of hydroxyl groups occurs. This method permits the identification of a suite of carboxyl-containing aromatic and aliphatic compounds, not previously observed in conventional pyrolysis, providing useful information on the biodegradation processes of plant materials leading to macromolecular humic substances. | Pyrolysis has been used for the last ten years to study the chemical nature of humic substances. However, obtaining data is hampered by analytical limitations. One of these is that carboxylic acids other than fatty acids are not usually present amongst pyrolysis products. To overcome this problem, a novel method-pyrolysis/methylation - is applied. Simultaneous pyrolysis/derivatization with tetramethylammonium hydroxide protects the carboxyl groups by formation of methyl esters. At the same time, partial methylation of hydroxyl groups occurs. This method permits the identification of a suite of carboxyl-containing aromatic and aliphatic compounds, not previously observed in conventional pyrolysis, providing useful information on the biodegradation processes of plant materials leading to macromolecular humic substances.

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