Highly reproducible capillary zone electrophoresis of humic acids in cyclodextrin- or oligosaccharide-modified background electrolytes

Capillary zone electrophoresis has been used for the characterization and separation of humic acids. It was found that addition of saccharides like α-, β-, γ-cyclodextrins, maltose, hydroxyethylcellulose or dextran sulfate in the background electrolyte (50 mM Na2B4O7, pH 9.6) yields better separation patterns and highly reproducible electropherograms. Electropherograms with higher numbers of peaks and high reproducibility were obtained with α- and β-cyclodextrins or with a mixture of α-+γ-cyclodextrin-modified background electrolytes. Separation was carried out with the cathode at the detector end of the column. Adsorption of humic acids to the capillary wall was diminished using an epoxy-coated capillary tube.