Continuous postcolumn detection of underivatized polysaccharides in high-performance liquid chromatography by reaction with permanganate.

We describe a continuous postcolumn reaction system for colorimetric detection of carbohydrates suitable for use with both preparative and analytical HPLC separations. A fraction of the effluent from the column is mixed via a T-junction with a 0.02% solution of potassium permanganate in 3 M sulfuric acid. The mixture then passes through a reaction coil heated to 100 degrees C, and its absorbance at 525 nm is continuously monitored. Bleaching of the permanganate is proportional to the sugar concentration. The major advantages of the detection system are its mass rather than molar sensitivity and insensitivity to changes in nonoxidizable buffer concentrations. As little as 0.1 micrograms of sugar can be detected. These features make the system suitable for detection, with high sensitivity, of polysaccharides using gradient elution from ion-exchange columns.