## 1 Introduction  
Cellulose is a natural, biodegradable and biocompatible resource, and represents about 50% of the associated carbon on earth. Its interest as a source of fibers in paper industry, textiles and materials, and more recently as a source of glucose for bio-ethanol production or a novel sugar-based chemistry, is constantly growing. For all these applications, the determination of molar masses, both average value and distribution is more and more expected, as they are key parameters to control and improve the industrial processes as well as the final product properties. Size Exclusion Chromatography (SEC) is nowadays the favorite technique for this type of characterization, and several analytical methods have been established since the early 70's. They mainly differ from each other with respect to the cellulose dissolution step prior to SEC analysis. During the 70's and 80's, indirect dissolution was preferred, through the synthesis of non-polar cellulose derivatives, such as cellulose tricarbanilates (CTC) [1; 2; 3; 4; 5]. From the 90's, direct dissolution methods, without any derivatization, using polar solvent mixtures like lithium chloride/\(N\),\(N\)-dimethylacetamide (LiCl/DMAc) have emerged [6; 7; 8]. [PERSON] et al. [6] have used lithium chloride/\(N\),\(N\)-dimethylacetamide (LiCl/DMAc) as solvent system for cellulose characterization by SEC, and reported the stability, solubility and dissolving states of cellulose in this solvent system. Subsequently, LiCl/DMAc has been favorably used for cellulose molar mass distribution (MMD) characterization particularly on birch wood Kraft pulp, hardwood or softwood Kraft pulps or aged papers [9; 10; 11; 12; 13; 14; 15]. Several works [16; 17; 18] reported cellulose dissolution in LiCl/DMAc without degradation, despite a slight decrease of the viscosity of cellulose solutions after 30 days has been observed [6]. However, some relevant problems concerning the use of LiCl/DMAc have been described: (i) the aggregation of cellulose in the solution depending on dissolution conditions and concentrations of cellulose or LiCl [19]; (ii) incomplete dissolution of several cellulose samples [20; 21] and (iii) detrimental degradation of cellulose by heating in DMAc or LiCl/DMAc during the dissolution process [22], especially for high molecular weight samples. Consequently, cellulose characterization by SEC analyses using LiCl/DMAc as solvent is still currently a topic a numerous researches [23]. Other solvent systems have also been studied, such as LiCl/DMI described by [PERSON] and [PERSON] [24; 25]. TBAF/DMSO has been reported to be a good solvent for various cellulose samples, without affecting significantly their physical structure [26; 27]. Even if the dissolution mechanism was not clearly explicated yet, it has been accepted that: (i) DMSO is an excellent swelling agent for cellulose, increasing the accessibility to hydrogen bonds; (ii) the fluoride ion, due to its strong hydrogen bond acceptor character, can then reduce the intermolecular attraction between the polysaccharide chains and disrupt the hydrogen bonds network [27]. For this reason, this system appears as a suitable candidate for SEC analysis of cellulose samples. Additionally, the replacement of a carcinogenic solvent such as DMAc by DMSO could be of interest for the health of the operators and for the environment. DMSO is classified as nontoxic with no risk for the human health according to US Environmental Protection Agency (EPA). Finally, DMSO is present in some industrial wastewaters and is readily biodegradable [28], and could be synthesized from renewable raw materials in the future. The size exclusion separation mechanism is based on differences in the solute hydrodynamic volumes. Different methods can be used to obtain the molar mass of the components of chromatographed samples [29].