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 s eparation of humic acids. It was found that addition of saccharides like al pha-, beta-, gamma -cyclodextrins, maltose, hydroxyethylcellulose or dextra n sulfate in the background electrolyte (50 mM Na2B4O7, pH 9.6) yields bett er separation patterns and highly reproducible electropherograms. Electroph erograms with higher numbers of peaks and high reproducibility were obtaine d with alpha- and beta -cyclodextrins or with a mixture of alpha-+gamma -cy clodextrin-modified background electrolytes. Separation was carried out wit h 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. (C) 2000 Elsevier Science B.V. All rights reserved.