Analysis of birch wood lignin by oxidative degradation

Summary The lignin in birch wood has been subjected to analysis by oxidative degradation after milling of wood samples in a Wiley mill and in a rotatory ball mill. For comparison milled wood lignin from birch has also been analysed. It was found that the type of milling affects both the total yield of degradation acids and their relative frequency of occurrence. These findings are interpreted as being due to a cleavage of aryl ether linkages during the milling procedure. The oxidative degradation analysis gave rise to a total of 30 different acids which were tentatively identified on the basis of their mass spectral fragmentation patterns. Among the acids some were found having either a phenoxyacetic acid or a phenoxypropionic acid structure. The possible origin of these is discussed. A grant to one of us (R.A.N.) from Jacob Wallenbergs Forskningsstiftelse is gratefully acknowledged. Thanks are due to Kristina Gustafsson for skilful experimental assistance