Malešič Jasna, Kraševec Ida, Kralj Cigić Irena
Library Research Department, National and University Library, Turjaška 1, 1000 Ljubljana, Slovenia.
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna Pot 113, 1001 Ljubljana, Slovenia.
Polymers (Basel). 2021 Jun 17;13(12):1990. doi: 10.3390/polym13121990.
Determination of cellulose degree of polymerization (DP) is one of the most commonly used methods in paper degradation studies, performed either by a standardized method using viscometry (as average degree of polymerization (DP)) or size-exclusion chromatography (SEC) (as weight average molecular mass (M)). Due to the insolubility of papers with high lignin content in cupriethylenediamine (CED), such as groundwood papers, viscometric determination is not possible; therefore, pretreatment is required to allow subsequent dissolution of the papers. In this study, the pretreatment of historical papers containing groundwood with sodium chlorite in acetic acid was investigated, which enables dissolution of the paper samples in CED and determination of the cellulose average degree of polymerization by viscometry (DP). Kappa number was determined to estimate the lignin content in the papers. The suitability of SEC UV-VIS analysis for determination of M in papers with high lignin content had been verified before it was used as a comparative method for viscometry. Using SEC, changes in the weight average molecular mass (M) of cellulose tricarbanilate (CTC) derivative during delignification were evaluated. The results indicate that no significant depolymerization occurred in the selected samples under the studied delignification conditions, which was additionally confirmed with determination of monosaccharides by ion chromatography. The results of the M determinations by SEC and DP by viscometry are in good correlation, justifying the use of viscometry after chlorite/acetic acid pretreatment to determine the cellulose average degree of polymerization in historical papers with high lignin content.
纤维素聚合度（DP）的测定是纸张降解研究中最常用的方法之一，可通过使用粘度测定法的标准化方法（作为平均聚合度（DP））或尺寸排阻色谱法（SEC）（作为重均分子量（M））来进行。由于高木质素含量的纸张（如磨木浆纸）在铜乙二胺（CED）中不溶，因此无法进行粘度测定；所以，需要进行预处理以使纸张随后能够溶解。在本研究中，对用亚氯酸钠在乙酸中对含磨木浆的历史纸张进行预处理进行了研究，这使得纸张样品能够溶解在CED中，并通过粘度测定法测定纤维素平均聚合度（DP）。测定卡伯值以估计纸张中的木质素含量。在将SEC紫外可见分析用作粘度测定法的比较方法之前，已验证了其对测定高木质素含量纸张中M的适用性。使用SEC，评估了脱木质素过程中三苯氨基甲酸纤维素酯（CTC）衍生物的重均分子量（M）的变化。结果表明，在所研究的脱木质素条件下，所选样品中未发生明显的解聚，这通过离子色谱法测定单糖得到了进一步证实。通过SEC测定M和通过粘度测定法测定DP的结果具有良好的相关性，证明了在亚氯酸盐/乙酸预处理后使用粘度测定法来测定高木质素含量历史纸张中纤维素平均聚合度的合理性。
