## 3 Results and Discussion
### Carboxymethylcellulose Characterization
#### 3.1.2 Physical Characterization
The DS range in the commercially available CMC samples is typically comprised between 0.4 and 1.5, with 3 being the maximum theoretical DS value [27]. The DS determined according to the ASTM D1439 standard [19] showed some differences between samples. For CMC1 and CMC4, no statistically significant (\(p>0.05\)) differences were found with both samples presenting an average DS of 0.71. On the other hand, for CMC3 and CMC4 statistically significant (\(p<0.05\)) differences were found, with CMC3 presenting the lowest DS (0.61) of all tested samples and CMC2 the highest (0.8). These data are in agreement with the information available in the product datasheets for CMC1 and CMC4 (0.79 and 0.70, respectively). In the case of CMC2, the product datasheet did not include this information, while for CMC3 the information stated that the DS range is between 0.75 and 0.85, which is significantly different from the result obtained here. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**Moisture (\%)**} & \multirow{2}{*}{**Purity (\%)**} & \multirow{2}{*}{**DS**} & \multicolumn{3}{c}{**Molar Mass Distribution**} \\ \cline{5-6}  & & & & & \(M_{w}\) (kDa) & **Mn (kDa)** & **PI** \\ \hline CMC1 & 3.67 \(\pm\) 0.19  & 0.71 \(\pm\) 0.03  & 370.1 \(\pm\) 7.2  & 313.0 \(\pm\) 6.3 & 1.2 \(\pm\) 0.0 \\ CMC2 & 11.74 \(\pm\) 0.04  & 97.23 \(\pm\) 0.55  & 0.80 \(\pm\) 0.01  & 471.7 \(\pm\) 1.0  & 382.6 \(\pm\) 6.0 & 1.2 \(\pm\) 0.0 \\ CMC3 & 5.09 \(\pm\) 0.12  & 99.55 \(\pm\) 0.33  & 0.61 \(\pm\) 0.01  & 407.0 \(\pm\) 2.3  & 316.4 \(\pm\) 3.7 & 1.3 \(\pm\) 0.0 \\ CMC4 & 5.97 \(\pm\) 0.24  & 99.57 \(\pm\) 0.25  & 0.71 \(\pm\) 0.00  & 322.5 \(\pm\) 9.0  & 288.9 \(\pm\) 8.5 & 1.1 \(\pm\) 0.0 \\ \hline \end{tabular} Note: DS—degree of substitution; MW—weight-average molar mass; Mn—number-average molar mass; PI——polydispersity index. Different letters represent the statistically significant differences (\(p<0.05\)) found between samples for the same condition.[ENDFOOTNOTE]  
\end{table} 
Table 1: T Physical characteristics of the commercial CMCs evaluated. Different letters represent the statistically significant (\(p<0.05\)) differences found between conditions. The molar mass distribution of CMC samples was determined using the standard curve for the molecular weight of polysaccharide patterns fromlinebreak ShodexTM [Log(MW) = -0.3615 (RT) + 10.162 with R2 of 0.981 (MW corresponds to the average molecular weight in Da, while RT is the retention time in minutes) and Equations (4)-(6). To obtain more rigorous data on the molar mass distribution, the chromatograms were sectioned and properly integrated. The results obtained according to Equation (4) showed that all samples had statistically significant (\(p<0.05\)) different \(M_{w}\)s, with the average \(M_{w}\) of 370.1, 471.7, 407.0, and 322.5 KDa for CMC1, 2, 3, and 4, respectively. Generally, the increase in \(M_{w}\) led to an increase in viscosity of the aqueous solutions of CMC samples, which could have a negative impact on the biological properties studied due to the reduced availability of the CMC for interaction with different components in the cells.