Understanding and improving direct UV detection of monosaccharides and disaccharides in free solution capillary electrophoresis

tDirect UV detection of carbohydrates in free solution capillary electrophoresis at 270 nm is made possibleby a photo-oxidation reaction. Glucose, rhamnose and xylose were shown to have unique UV absorptionspectra hypothesizing different UV absorbing intermediates for their respective photo-oxidation. NMRspectroscopy of the photo-oxidation end products proved they consisted of carboxylates and not malon-dialdehyde as previously theorized and that oxygen thus plays a key role in the photo-oxidation pathway.Adding the photo-initiator Irgacure®2959 in the background electrolyte increased sensitivity by 40% atan optimum concentration of 1 × 10−4mM and 1 × 10−8mM for conventional 50 μm i.d. capillaries andfor the corresponding extended light path capillaries, respectively.