Determination of arylglycerol-beta-aryl ethers and other linkages in lignins using DFRC/P-31 NMR

An analytical method for lignins has been developed that involves derivatiz ation followed by reductive cleavage (DFRC), depolymerization, and quantita tive P-31 NMR spectroscopy. This technique detects and quantifies the vario us ether linkages present in softwood residual kraft lignins (RKL) and mill ed wood lignins (MWL). In addition, the technique supplies new quantitative information about beta -aryl ethers linked to condensed and noncondensed a romatic moieties, including dibenzodioxocins. Within RKL, beta -aryl ether bonds connected to condensed phenolic moieties predominated over those conn ected to noncondensed phenolic moieties. In addition, the amount of DFRC mo nomers determined by gas chromatography was minute in the RKL but large in the MWL. This indicates that almost all noncondensed beta -aryl ether linka ges were cleaved during kraft pulping. The method offers new avenues for. t he detailed investigation of the bonding patterns of native and technical l ignins.