Influence of pH*-value of methanolic electrolytes on electroosmotic flow in hydrophilic coated capillaries

The dependency of EOF on the H+-concentration and the related so called pH* value of methanolic electrolytes has been examined with poly(ethylene glyc ol) (PEG), poly(vinyl alcohol) (PVA) and uncoated capillaries. These result s were compared with the pH dependency of EOF of these capillaries using aq ueous buffers. In uncoated capillaries the dependency of EOF on the pH(*)-v alue is very similar for aqueous and methanolic electrolytes. The EOF incre ases with increasing H+-concentration and pH-hysteresis is observed. In PVA coated capillaries the EOF is strongly reduced over wide pH* or pH ranges for both methanolic electrolytes and aqueous buffers. The EOF in PEG coated capillaries is surprisingly directed to the anode with methanolic electrol ytes whereas a reduced cathodic EOF is observed in aqueous electrolytes. Th e anodic EOF of PEG-coated capillaries in methanolic electrolytes is indepe ndent of the pH*-value. The usefulness of PEG- and PVA-coated capillaries f or adjusting the EOF in non-aqueous electrolytes for the analysis of isomer ic organic acids was demonstrated. (C) 2000 Elsevier Science B.V. All right s reserved.