# Determination of Cellulose Degree of Polymerization in Historical Papers with High Lignin Content
## 3 Results and Discussion
### Stability of Cellulose during Delignification  
The degradation of paper samples during the process of delignification was followed by SEC using a UV-VIS detector. Figure 1 shows the relative signals of the CTC derivatives for the untreated and treated paper sample No. 1 for 3, 6, and 9 h. The CTC fraction appears as the highest molecular mass, and its distribution is much wider than that of the fraction of hemicellulose tricarbonilates, which have lower molecular masses [11]. The SEC analysis of Whatman filter paper No. 1 confirmed that the signal with broader distribution represents molecules of cellulose CTC derivatives (data not shown). From Figure 1, it can be concluded that the changes in molecular mass of cellulose after delignification for 3, 6, or 9 h are not significant (for sample No. 1, the M\({}_{\mathrm{w}}\) difference is 1%). Kappa number of sample No. 1 was reduced from over 100 to 19 during delignification (Table 2). From the CTC signal of the untreated sample No. 1, which is only slightly different from the signals of the delignified samples, it can be concluded that the molecular mass of cellulose is not significantly changed, but differences in the lower molecular mass range are observed, especially between the untreated and delignified paper samples (Figure 1, Sample No. 1, untreated and after delignification for 3 h). The hemicellulose distribution is slightly reduced with longer delignification (Figure 1, delignification for 3, 6, or 9 h), suggesting that the delignification procedure could influence the degradation of hemicellulose. Therefore, to evaluate the degradation of the cellulosic and hemicellulose polymer due to chlorite oxidation, the content of monosaccharides in the undiluted filtrates of the reaction mixtures after delignification was determined by ion chromatography for paper sample No. 1 (Table 3). The monosaccharides detected were glucose, galactose, xylose, and arabinose, whose amounts in the first filtrates after 6 h of delignification were higher than after 3 h of delignification, as expected. Although their amount in both first filtrates is very low, the results are in agreement with the results of SEC (Figure 1). In the second filtrate, the amounts of monosaccharides were even lower, which is to be expected since a new portion of the reaction mixture was added. The content of monosaccharides released during delignification (Table 3) is also low compared to the average values of monosaccharides previously determined in different paper documents [24]. The content of glucose released after 6 h of delignification is less than 0.00005%, which is not significant  
Figure 1: Molecular mass distribution of CTC derivatives for sample No. 1, untreated (0 h) and after delignification for 3, 6, or 9 h.  
compared to over 70% of glucose content measured in papers produced from 1950 to 2007 [24]. The content of arabin after 6 h of delignification is less than 0.005%, which is also low compared to average amounts of arabin in papers produced during the same period (1.54-1.7%) [24]. Therefore, the results presented in Table 3 additionally confirm that the degradation of cellulose or hemicelluloses during acid/chlorite treatment is not intense under the described conditions. The results are consistent with those reported in the literature [19], where samples of Kraft linerboard pulp exposed to the acid-chlorite delignification procedure were analyzed to evaluate degradation during treatment. The Klason lignin content of the unbleached linerboard pulp was 19.1%. The pulp samples were exposed to the delignification process several times. The molecular mass distribution curves showed that after two delignification treatment cycles there was no degradation of the cellulose, resulting in pulp with 3.2% Klason lignin content. After further delignification treatment cycles, the signal of the cellulose shifted to lower molecular masses, indicating significant cellulose degradation.