A Sensitive Derivatization Method for the Determination of the Sugar Composition after Pre‐column Reductive Amination with 3‐Amino‐9‐ethylcarbazole (AEC) by High‐Performance Liquid Chromatography

3‐Amino‐9‐ethylcarbazole (AEC) was employed for monosaccharide derivatization. The derivatives can be analyzed by high‐performance liquid chromatography (HPLC) with an ultraviolet detection (wavelength: 254 nm). Monosaccharides were quantitatively derivatized with 3‐amino‐9‐ethylcarbazole (AEC) at 70 °C for 60 min. The method was linear for all samples over the concentration range tested ( r >0.999), the precision was found to be satisfactory (R.S.D.<3%), and the recovery ratios were >98.62%. The stability analysis showed R.S.D. was between 1.81% –3.16%. Detection limits for the samples ( D ‐glucose, L ‐xylose, D ‐mannose, L ‐arabinose, and L ‐rhamnose) ranged from 0.06 to 1.97 ng/mL ( S/N =3). Under the optimized derivatization and HPLC conditions, five monosaccharides were well separated using a narrow bore C18 column (250 mm×4.6 mm) with 0.1 mol/L ammonium acetate containing 25% acetonitrile at a flow rate of 0.5 mL/min. As an application, the method has been successfully applied to the determination of monosaccharide compositions of three polysaccharides SPPA‐1, SPPB‐1 and SPPC‐1 of Spirulina platensis . This method also has potential application to oligosaccharide or glycan analyses.