BEHAVIOR AND USE OF NONAQUEOUS MEDIA WITHOUT SUPPORTING ELECTROLYTE IN CAPILLARY ELECTROPHORESIS AND CAPILLARY ELECTROCHROMATOGRAPHY

Five nonaqueous solvents (acetonitrile, methanol, N,N-dimethylformamid e, dimethyl sulfoxide, formamide) and deionized water were investigate d for their ability to support electroosmotic now (EOF) without electr olytic additives, In general, now was found to be equal to or greater than now with typical CE buffer systems. The magnitude of EOF was dete rmined for each solvent by open tubular capillary electrophoresis (CE) and related to viscosity (eta), dielectric constant (epsilon), and th e ratio of dielectric constant to viscosity (epsilon/eta). Zeta potent ials (zeta) were derived indirectly from now data and tabulated, Compa risons of flow behavior and zeta were made between pure solvents and c onventional CE buffers, and questions of equilibration and reproducibi lity were addressed. Similar experiments were performed using hydroorg anic mobile phases (ACN/water, MeOH/water) across the complete composi tional range (100% water-100% organic), with flow characteristics and zeta reported for each mobile phase system. Packed capillary columns ( 5-mu m ODS) were evaluated for now and retention stability under capil lary electrochromatographic (CEC) conditions. A separation of 11 polyc yclic aromatic hydrocarbons was performed in under 13 min by CEC with an ACN/water mobile phase, Reduced plate heights (h) were calculated b etween 2.5 and 3.0 for solutes with capacity factors (k') up to 4.5 fo r the most retained solute.