EFFECTS OF CAPILLARY TEMPERATURE CONTROL AND ELECTROPHORETIC HETEROGENEITY ON PARAMETERS CHARACTERIZING SEPARATIONS OF PARTICLES BY CAPILLARY ZONE ELECTROPHORESIS

The effect of system parameters and particle properties on separations by capillary zone electrophoresis have been determined for mixtures of charged polystyrene latex particles. Maintenance of constant capillary temperature by a thermostated system significantly reduced the large dependencies on voltage of mobilities, selectivity, efficiency, and resolution which were observed on a nonthermostated system. Electrophoretic heterogeneity (i.e., microheterogeneity) in the particle samples was determined to be the major source of zone broadening on the thermostated system. Since zone broadening due to electrophoretic heterogeneity is independent of voltage, the observed efficiencies were independent of voltage. Resolution was also found to be independent of voltage. The observed independence of efficiency on voltage indicated that particle-wall interactions were negligible and that the separations were electrophoretic in nature. The relative standard deviation of the mobility distribution for a 0.07-mu-m carboxylate-modified latex was determined to be 1.5%, which led to an efficiency of only 4400 theoretical plates. The large efficiency losses resulting from electrophoretic heterogeneity decrease restrictions on other broadening sources. Thus, when zone broadening Is dominated by electrophoretic heterogeneity, larger injection and detection volumes, capillary inner diameters, and operating powers can be employed without any significant further loss of efficiency or resolution.