A review of advanced strategies for molecular weight determination of insoluble polysaccharides: Developments and...

Molecular weight is a critical factor in understanding the chemical and physical properties of polysaccharides. For soluble polysaccharides, many established and reliable methods are available. However, determining the molecular weight of insoluble polysaccharides presents significant challenges. Traditional methods like gel-permeation chromatography/size-exclusion chromatography (GPC/SEC), nuclear magnetic resonance (NMR), and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry are typically unsuitable for direct application in analyzing insoluble polysaccharides. This review explores the innovative strategies designed to address these obstacles, categorizing them into two primary groups: intact and non-intact methodologies. Intact approaches include techniques like solid-state NMR, Fourier Transform Near-Infrared (FT-NIR) spectroscopy and fluorescence lifetime measurements which enable direct molecular weight determination without additional processing. In contrast, non-intact methods, such as derivatization processes, the use of dipolar aprotic solvents, and ionic liquids, involve dissolving the polysaccharides in specialized solvents before analysis with conventional instruments like NMR, MALDI, or SEC. This review discusses the advantages and limitations of each strategy, highlights the emerging role of molecular modeling in characterizing complex polysaccharide structures, and outlines future trends and advanced techniques that promise to enhance analytical accuracy. It also provides a comparative analysis to guide researchers in selecting the most appropriate method for their specific polysaccharide study needs.