Pyrolysis of Lignin in the Presence of Tetramethylammonium Hydroxide: A Convenient Method for S/G Ratio Determination

Pyrolysis-gas chromatography in the presence of tetramethylammonium hydroxide (TMAH) was applied to the determination of the ratio of the abundances of the syringyl β-aryl ether subunits to those of the guaiacyl equivalents (S/G) in lignin. Diazomethane-methylated kenafs (Hibiscus cannabinus and Hibiscus sabdariffa) and beech (Fagus crenata) in situ lignins were employed. Relative abundances of pyrolysis products derived from the guaiacyl and syringyl β-aryl ether subunits were determined. The S/G ratios for in situ lignins were obtained with average 3.1% relative standard deviation for a minimum of six repeated runs. The S/G ratios determined by pyrolysis in the presence of TMAH agreed well with those determined by thioacidolysis, with a significant linear regression (R 2 = 0.9867). The results showed that pyrolysis with TMAH is an effective tool for obtaining information on the S/G ratio for in situ lignins.