Behavior and Use of Nonaqueous Media without Supporting Electrolyte in Capillary Electrophoresis and Capillary Electrochromatography

摘要

Five nonaqueous solvents(acetonitrile, methanol, N, Ndimethylformamide, dimethyl sulfoxide, formamide)and deionized water were investigated for their ability to support electroosmotic flow (EOF) without electrolytic additives. In general, flow was found to be equal to or greater than flow with typical CE buffer systems. The magnitude of EOF was determined for each solvent by open tubular capillary electrophoresis (CE) and related to viscosity(η), dielectric constant (ε), and the ratio of dielectric constant to viscosity (ε/η). Zeta potentiala (ξ) were derived indirectly from flow data and tabulated.. Comparisons of flow behavior andξ were made between pure solvents and conventional CE buffers, and questions, of equilibration and reproducibility were addressed. Similar experiments were performed using hydroorganic mobile phases (ACN/water, MeOH/water) across the complete compositional range (100% water- 100% or- ganic),with flow characteristics and ξreported for each mobile phase system. Packed capillary columns (5-μm ODS)were evaluated for flow and retention stability under capillary electrochromatographic (CEC) conditions. A separation of 11 polycyclic aromatic hydrocarbons was performed in under 13 min by CEC with an ACN/water mobile phase. Reduced plate heights (h) were calculated between 2.5 and 3.0 for solutes with capacity factors (k′) up to for the most retained solute.