CAPILLARY-ZONE-ELECTROPHORESIS WITH FLUID-IMPERVIOUS POLYMER TUBING INSIDE A FUSED-SILICA CAPILLARY

A fused-silica capillary was used as a mold in the in situ formation o f, and as a sheath for, a highly crosslinked poly(styrene-divinylbenze ne) inner tubing having 3-5 mu m wall thickness. This 'tube-in-the-tub e' construction with the thin-walled, fluid-impervious polymer inner t ubing precluded contact between the aqueous buffer solution and the in ner wall of the fused-silica capillary. As a result, this structure wi thstood long-term treatment with highly alkaline solutions without det erioration. In order to hydrophilize the inner surface of the polymer tube, a polyoxyethylene oligomer was grafted to its inner wall and sub sequently crosslinked. The inner tube with such hydrophilic coating wa s also stable to hydrolytic attack by 1 M NaOH. Although the nonpolar polymeric inner surface generated electrosmotic flow as if it had some fixed negative charges, the how velocity became almost negligibly sma ll once it had been hydrophilized. As illustrated by electropherograms , the hydrophilization of the polymeric inner tube greatly facilitated the CZE of basic proteins in the pH range from 3 to 6 without the nee d for additives in the electrophoretic medium to mask the silanol grou ps at the surface of quartz capillaries. (C) 1997 Elsevier Science B.V .