# Determination of Cellulose Degree of Polymerization in Historical Papers with High Lignin Content
## 3 Results and Discussion
### Reliability of the Results
For direct dissolution of nonderivatized cellulose and CTC, a round-robin test of cellulose SEC was performed using RI, MALS, and viscometry detectors [11]. The obtained weight average molecular mass values showed a variation of 36% across all methods. The two most important influencing parameters were sample preparation (derivatization and dissolution methods) and the type of molecular mass evaluation in SEC, i.e., by calibration or absolute measurements using light scattering. Both dissolution approaches gave acceptable results when the correct procedures were used [11]. In our research, the average molecular masses of carbonilated cellulose were determined from SEC analysis by calibration with polystyrene standards. The molecular masses are, therefore, relative values, since the SEC separation is based on the hydrodynamic volume of the analytes, which is an approximation of the molecular mass. [PERSON] et al. [11] have shown that overestimation of molecular mass is mainly due to differences in hydrodynamic radii in solutions of CTC derivatives as compared to calibration samples, such as pullulan or polystyrene. In previous studies, the weight average molecular masses (M\({}_{\rm w}\)) were compared with those determined using SEC coupled to a multiangle light scattering photometer (SEC MALS), and a fairly good correlation between the results was observed [38]. In addition to the systematic errors obtained with the UV-VIS detector, it is important to consider that although intralaboratory repeatability (precision) is high, the interlaboratory reproducibility (accuracy) is not as good [11; 37]. Gaussian curve deconvolution in the range representative for cellulose, hemicelluloses, or aggregates [23] was not applied to the molecular mass distribution curves because, as described in the previous section, cellulose signals do not change significantly during delignification. According to the results of SEC, the hemicellulose contents in the paper samples were significantly lower, less than 30%. Moreover, in paper samples with highly degraded cellulose, only the signals of hemicelluloses and low molecular masses of cellulose derivatives were observed after SEC analysis, which cannot be properly deconvoluted. It was therefore decided not to recalculate the weight average molecular masses to avoid additional systematic errors due to the deconvolution of the molecular mass distribution curves. Although the degradation of hemicelluloses during delignification could systematically lower the Mw values of cellulose obtained without deconvolution, it is assumed that the systematic error is negligible based on the results of SEC and the determination of monosaccharides in the undiluted filtrates (Table 3). The average DP\({}_{\rm v}\) values determined using viscometry are systematically lower, which is probably the consequence of noncellulosic components in the paper samples. They contribute to the mass of the sample but not to the viscosity of the analyte. Additional systematic errors can also be attributed to the degradation of oxidized cellulose samples in the CED solvent [39; 40], although some researchers claim that, contrary to these findings, viscometry gives results that are generally consistent with those obtained using SEC [1], even for the most degraded samples.