A new rapid technique for the characterization of lignin in vascular plants: thermochemolysis with tetramethylammonium hydroxide (TMAH)

Flash pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) has been utilized for the characterization of lignin in a gymnosperm (pine), angiosperm (alder), and nonwoody (Juncus effusus L.) vascular plant tissue. The gymnosperm tissue yielded primarily methylated guaiacyl derivatives resulting from cleavage of lignin β-O-4 bonds and subsequent methylation of acidic hydroxy groups. The angiosperm tissue also yielded guaiacyl-type compounds in addition to an analogous suite of methylated syringyl lignin derivatives. The nonwoody angiosperm yielded methylated cinnamyl lignin derivatives in addition to methylated guaiacyl and syringyl compounds. Analysis of alder wood with this technique at a low temperature of 310°C has demonstrated that the dominant reaction with TMAH is mainly a thermally assisted chemolytic degradation rather than degradation induced by pyrolytic bond cleavage. Accordingly, we now call the technique TMAH thermochemolysis.