Combined Effects of Molecular Size and Electroendosmotic Flow on the Capillary Electrophoretic Behaviour of Humic Substances

✍ Scribed by De Nobili, M. ;Bragato, G. ;Mori, A.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 182 KB
• Volume: 26
• Category: Article
• ISSN: 0323-4320
• DOI: 10.1002/(sici)1521-401x(199805)26:3<186::aid-aheh186>3.0.co;2-m

✦ Synopsis

The electroendosmotic flow (EOF), generated by the migration of solvated ions near the charged capillary surface, is an important factor in determining the capillary electrophoretic behaviour of humic substances (HS). We investigated the electrophoretic mobilities of HS fractions of reduced molecular-weight polydispersity extracted from peat and from a spodosol either in the presence or after suppression of the EOF. When the EOF was not suppressed, HS migrated to the cathode in spite of their negative charge. Fractionation of HS according to molecular size was achieved in polyacrylamidecoated capillaries filled with 0.05 M tris-phosphate buffer. In uncoated capillaries filled with the same buffer, all fractions had very close mobilities. Addition of polyethylene glycol MW 4 000 at concentrations above its entanglement threshold caused the migration times of larger molecules to increase more than those of smaller molecules. The separation was a linear function of molecular size up to 75 000 g mol -1 for peat HS and to 50 000 g mol -1 for HS extracted from the spodosol.