Chromophoric content in wood and mechanical pulps

The contents of chromophoric and leuchochromophoric structures in wood mate rial and how the contents of these structures change through the TMP proces s, have been investigated. As an analytical tool, light absorption spectra of wood and pulps in the region from 300-700 nm have been recorded. The spe ctra were obtained from reflectance measurements and subsequent calculation s using the Kubelka-Munk theory. The greatest chemical changes in the wood material seem to occur already during the first refining stage. The light a bsorption increases significantly in the UV-region, indicating the formatio n of e.g. aromatic alpha -carbonyl and/or conjugated aromatic structures. T he formation of this kind of structures can be reduced by treating the wood chips with DTPA and sodium sulphite before refining.