Syntheses of lignin-derived thioacidolysis monomers and their uses as quantitation standards

Analytical thioacidolysis releases diagnostic monomers from lignins by selectively cleaving alkyl aryl ether bonds. High yielding syntheses of the three thioacidolysis monomers were developed, and the compounds were used as standards for gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) quantitation of monomers released from lignocellulosics. First, syringyl, guaiacyl, and p-hydroxyphenyl glycerols were synthesized from the corresponding ethyl cinnamates and used as thioacidolysis substrates to prepare the monomers in high yields. These monomers were then used as standard compounds to measure their GC-MS and GC-FID response factors against two internal standards, 4,4'-ethylenebisphenol and tetracosane. For quantitation, it was shown that 4,4'-ethylenebisphenol is the better internal standard for GC-MS, whereas tetracosane remains the choice for GC-FID. When the obtained response factors were applied, the thioacidolysis monomer yields from white spruce, loblolly pine, poplar, bamboo, and sugar cane bagasse were determined by GC-MS. The obtained results were consistent with those reported in the literature.