Carbohydrate chromatography: towards yoctomole sensitivity.

In attempting to analyse complex carbohydrates by HPLC or capillary electrophoresis (CE) the chromatographer is faced with many challenges. The diversity of oligosaccharide structures described the date and their poor resolution on many chromatographic systems present a significant challenge to the chromatographer. In addition to this, the non-chromogenic nature of most carbohydrates greatly decreases the sensitivity of UV detection and refractive index is not an option for sensitive analysis. Over the last five years there have been significant advances in separation and detection methods for carbohydrates, and in this paper we will attempt to describe the most significant advances and highlight potential future developments. The detection of 200-300 fmol (2-3 x 10(-3) mol) of oligosaccharides can now be readily achieved using electrochemical detection or fluorescence detection (after labelling) with conventional HPLC columns and detectors. Miniaturized separation systems have greatly increased sensitivities with a CE-laser induced fluorescence instrument detecting as little as 100 yoctomoles (1 x 10(-22) mol).