High-performance liquid chromatography with evaporative light scattering detection for the determination of monosaccharides, mannitol and uronic acids in brown seaweed.

The determination of the monosaccharide composition of brown seaweed is crucial for understanding the polysaccharides responsible for many biological and functional properties of the raw material. This study aimed to develop a High-Performance Liquid Chromatography with Evaporative Light Scattering Detection (HPLC-ELSD) method for the separation and detection of monosaccharides (L-rhamnose, d-galactose, d-glucose, d-mannose, l-fucose, d-xylose), mannitol, and uronic acids (D-mannuronic and l-guluronic acid) in brown seaweed samples. Separation was achieved under hydrophilic interaction liquid chromatography (HILIC) conditions on an XBridge Amide column with a mobile phase consisting of acetonitrile/water/100 mM ammonium formate buffer at pH 3, in a total run time of 55 min. To enable accurate quantification, mutarotation equilibria were determined for all analytes, including mannuronic and guluronic acid. Accuracy was acceptable, with recoveries ranging from 84.7-120.9% for monosaccharides (with two outliers for fucose of 197% and 142%) and 99.5-134.8% for uronic acids, with an average recovery for all compounds of 102 ± 13.6%. Application to hydrolyzed samples of Ascophyllum nodosum, Alaria esculenta, and Fucus serratus confirmed method feasibility, though lower repeatability and accuracy highlighted limitations of current hydrolysis procedures and the need to further optimize biomass hydrolysis methods.