# Determination of Cellulose Degree of Polymerization in Historical Papers with High Lignin Content
## 3 Results and Discussion
### Stability of Cellulose during Delignification
The lignin content could be a contributory factor responsible for the overestimated M\({}_{\text{w}}\) values in the cellulose tricarbanilate derivatives in the conventional calibration, but it cannot be the only or the decisive one. However, the results showed that derivatization of pure cellulose produced the most homogeneous derivative (RSD 1%) and the untreated dissolving pulp caused less problems compared to its bleached version (RSD 4.5 vs. 12%) [11]. The differences in weight average molecular masses (Table 4) are not significant and can also be attributed to the inhomogeneity of the paper samples; thus, for the selected samples, it can be concluded that delignification does not induce any significant cellulose degradation. It has been demonstrated that degradation is more pronounced for new papers than for aged or historical paper samples, as only minor differences in average DP\({}_{\text{v}}\) determination occurred in aged newsprint during 5 h of delignification [12]. In the study by [PERSON] et al. [20], it was reported that the acid-chlorite delignification procedure caused a drastic reduction in the average degree of polymerization for cellulose from filter paper. The same author demonstrated that sodium chlorite delignification of various cellulose biomass samples under a higher concentration of the agents reduces the molecular mass of cellulose [23]. Other studies [9; 19] have proved that in a conventional lignocellulosic sample, lignin protects the polysaccharides from degradation by acid hydrolysis and oxidative cleavage during acid-chlorite delignification. However, once the lignin content is reduced to below about 1%, the polysaccharides are susceptible to degradation. At this point, the acid-chlorite treatment begins to affect the hemicelluloses and eventually attacks the cellulose component; at levels below 1% lignin, delignification can significantly damage the polysaccharide components [19]. It can be concluded that for the selected lignocellulosic historical paper samples, where the lignin content was reduced to a value of about 3%, no significant depolymerization of cellulose was observed during acid-chlorite delignification for up to 9 h, in agreement with the literature data [19]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Sample No.**} & **M\({}_{\text{w}}\) Before Delignification** & **M\({}_{\text{w}}\) After Delignification** & **M\({}_{\text{w}}\) Difference** \\  & **(mg\(\cdot\)L\({}^{-1}\))** & **(mg\(\cdot\)L\({}^{-1}\))** & **(\%)** \\ \hline
1 & 989,500 & 971,000 & 1 \\
2 & 1,117,000 & 1,026,000 & 6 \\
3 & 1,127,000 & 1,027,000 & 7 \\
4 & 486,000 & 527,500 & 6 \\
5 & 867,000 & 997,000 & 10 \\
6 & 1,011,500 & 963,000 & 3 \\
7 & 939,000 & 900,500 & 3 \\
8 & 914,500 & 803,000 & 9 \\
9 & 755,000 & 727,500 & 3 \\
10 & 663,000 & 685,500 & 2 \\
11 & 695,500 & 735,000 & 4 \\
12 & 1,040,500 & 970,000 & 5 \\
13 & 471,000 & 447,000 & 4 \\
14 & 351,000 & 350,500 & below 1 \\
15 & 363,000 & 412,000 & 9 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Weight average molecular mass (M\({}_{\text{w}}\)) for CTC derivatives of the samples before and after delignification. The measurements were performed in duplicates. Relative standard deviation for M\({}_{\text{w}}\) determinations was below 5%.