SUGAR (Ligand Exchange Chromatography

HPLC-based analyses of saccharides and sugar alcohols are performed in various modes, such as HILIC, ligand exchange, size exclusion, and ion exchange.

 

In the SUGAR series columns, a hard styrene-divinylbenzene copolymer designed for saccharide analysis is used as the base material, and a strong cation exchange resin incorporating functional sulfo-groups coupled with metal counter ions is used as the packing. Columns of the SUGAR series are available in various types according to counter ion, pore size, and pore structure, showing differential selectivity for different saccharides.

 

The series are suitable for saccharide separation and analysis of foods, areas of biochemistry, and natural substances. Other items include the Asahipak GS-220 HQ polymeric packed columns for size exclusion mode to analyze water-soluble, low molecular weight dietary fibers, and the OHpak SB-800 HQ polymeric packed columns for size exclusion mode to analyze polysaccharides, as well as the SUGAR KS-800 columns.

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A strong feature of the Shodex SUGAR series columns resides in the mechanism of separation in the ligand exchange mode. Ligand exchange refers to a mode of separation based on the interaction (ligand exchange potential) between hydroxyl groups and metal ions to form a complex.

 

Saccharides exhibits an energy-stable chair conformation in 5-membered ring (furanose) or 6-membered ring (pyranose) forms. Since hydroxyl group on each carbon can take either equatorial or axial position, even two saccharides having the same molecular structures may have different three dimensional configurations. Ligand exchange mode separates saccharides using this configuration difference of the complex formed between saccharides' hydroxyl groups and metal ions.

 

As shown in the left figure, saccharides having a larger number of ax-eq-ax configuration (triplet) units form stronger complexes with metal ions. Meanwhile, as right figure shows, saccharides lacking such a triplet structure form complexes with ax-eq (pair) hydroxyl group. As the unit number of this pair structure increases, saccharides become more potent forming complexes with metal ions. The complex formation capacity also differs depending on modified metal ions.

 

The complex formation potential also differs depending on the kind of metal ion.

Ag+ < Li+ < Na+ < Zn2+ < Ca2+ < Ba2+ < Pb2+

When using a column of the SUGAR series, analysis should be performed at increased column temperatures to prevent anomer separation. Under strongly alkaline conditions, saccharides are likely to isomerize with the fear of decomposition of polysaccharides.