Effects of pore flow on the separation efficiency in capillary electrochromatography with porous particles

The effect of pore now on the separation efficiency of capillary electrochr omatography (CEC) has been studied using columns packed with particles with different pore sizes. A previously developed model was used to predict the (relative) pore flow velocity in these columns under various experimental conditions. Equations are derived describing the effect of pore now on peak broadening in CEC, The theory has been compared with practice in the rever sed-phase CEC separation of various polyaromatic hydrocarbons. It is shown, by theory and experimentally, that the mass-transfer resistance contributi on to peak dispersion can be effectively eliminated when using porous parti cles with a high (greater than or equal to 50 nm) average pore diameter. Mo reover, at high pore-to-interstitial now ratios the flow inhomogeneity cont ribution (the A term in the plate height equation) is also shown to decreas e. Under optimal conditions, a reduced plate height of 0.3 for the nonretai ned compound could be obtained. It is argued that fully perfusive porous pa rticles can be a more efficient separation medium in CEC than nonporous par ticles.