Analysis of reducing carbohydrates by reductive tryptamine derivatization prior to micellar electrokinetic capillary chromatography

A micellar electrokinetic capillary chromatography method for determination of low molecular weight carbohydrates (dp 1-2) with an unbound carbonyl group as in aldoses or other reducing carbohydrates has been developed. Reductive amination of aldoses on the carbonyl group using tryptamine introduced a chromophor system to the carbohydrates enabling their sensitive UV detection at 220 nm and identification based on the indole group using diode array detection. Twelve carbohydrates including pentoses (D-ribose, L-arabinose, and D-xylose), hexoses (D-glucose, D-mannose, and D-galactose), deoxy sugars (L-rhamnose and L-fucose), uronic acids (D-glucuronic acid and D-galacturonic acid), and disaccharides (cellobiose and melibiose) are included in the study, using D-thyminose (2-deoxy-D-ribose) as the internal standard. Detection of all 12 carbohydrates is performed within 30 min. Linearity with correlation coefficients from 0.9864 to 0.9992 was found in the concentration range of 25-2500 mumol/L for all carbohydrates; the relative standard deviation on the migration times was between 0.27 and 0.80 min, and limits of quantification and limits of determination were in the picomole range.