Simultaneous Enantioseparation of Monosaccharides Derivatized with l-Tryptophan by Reversed Phase HPLC

Three reducing monosaccharides (glucose; Glc, galactose; Gal, and mannose; Man) were derivatized with l-tryptophan (l-Trp) under alkaline conditions. The dl-Gal and dl-Man derivatives were chirally resolved by HPLC with an acidic mobile phase, but the dl-Glc derivative was not. All of the three dl-monosaccharide derivatives were simultaneously enantioseparated using HPLC with a SunShell RP-AQUA column (C28) and a basic mobile phase. The optimum mobile phase conditions consisted of 5 mM phosphate and 25 mM tetraborate buffer (pH 9.6) at 20°C. With this system, resolution of d- and l-isomers of the Glc, Gal and Man derivatives were approximately 1.7, 2.2 and 2.4, respectively. When the three monosaccarides were derivatized with l-phenylalanine instead of l-Trp, dl-Gal and dl-Man were enantioseparated under both acidic and basic conditions, but dl-Glc was not. It was observed that enantiomer elution orders of the three monosaccharides derivatized with l-Trp were reasonably reversed when derivatized with d-Trp. It was also revealed that borate anions were required for simultaneous enantioseparation with HPLC.