Open tubular capillary electrochromatography in fused-silica capillaries chemically bonded with macrocyclic dioxopolyamine

In this paper, the macrocyclic dioxopolyamine compound: 1,4,7,10-tetraazacyclotridecane-11,13-dione was used as stationary phases with the aid of 3-(2-cyclooxypropoxyl)propyl-trimethoxy silane as bridge in open-tubular capillary electrochromatography (OTCEC). To increase the surface area and produce radial extensions from the surface, the capillaries were etched by aqueous sodium hydroxide before being coated. A comparison was made of the properties of capillary modified with the macrocyclic dioxopolyamine with those of the bare capillary by electroosmotic flow measurements and its dependence on pH. The direction of EOF on the capillaries modified with dioxo[13]aneN(4) is reversed at somewhat lower pH (pH<5.23). These modified capillaries had shown improved separations of neurotransmitters, isomeric nitrophenols, isomeric dihydroxybenzenes and isomeric aminophenols, in comparison with untreated capillaries. The plate numbers of the isomeric nitrophenols and dihydroxybenzenes were greater than 20,000/m and the reproducibility of migration time and the plate number was pretty good (R.S.D.<2.5%). (C) 2000 Elsevier Science B.V. All rights reserved.