A FT-ICR MS Study of Lignin: Determination of an Unusual Structural Repetitive Unit in Steam Exploded Lignin from Wheat Straw

GPC analysis of a steam exploded lignin from wheat straw showed M-w = 3605 and M-z = 21155 g/mol and a bimodal distribution with molecular weights in the range 100-10000 g/mol. On the contrary, FT-ICR-MS showed that fragments with a mass higher than 4534 Da cannot be obtained. Furthermore, FT-ICR MS showed that lignin is not a completely random polymer, but it showed some regularity with a difference of 44.026 m/z (C2H4O) between the peaks. The distribution of Kendrick mass defect (KMD) in function of Kendrick nominal masses (KNM) showed the same behavior.