Evaluation of surface lignin on cellulose fibers with XPS

XPS measurement of carbon and oxygen signals can be used in monitoring the surface lignin content of extracted wood pulp. However, surface analyses based on carbon and oxygen signals only may be unreliable due to surface contamination. We have evaluated the lignin content in over 250 chemical and mechanical pulp samples with XPS using two different analyses, in order to study the reliability and the reproducibility of the methods. The results indicate that under a strict experimental setup, surface contamination can be controlled. Both methods of analysis turn out to be consistent indicators of surface lignin content for a variety of extracted pulps processed under different conditions.