INTERACTION OF CAPILLARY ZONE ELECTROPHORESIS WITH A SHEATH FLOW CUVETTE DETECTOR

In a capillary zone electrophoresis system with a sheath flow detector, the pressurized detector Induces a component of flow opposite to that of electrophoresis. This pressure-induced flow, because of Its nonuniform velocity profile, can degrade the separation. However, theory predicts and experiment verifies that, under normal operating conditions, the detector does not degrade the separation. The major source of band broadening at pH 9 and 10 Is due to longitudinal diffusion, although lnlection volume can limit the performance of the system. When Injection volume Is minimized, over 2.5 million theoretical plates are obtained for the analysis of fluorescein thiocarbamyl derivatives of amino acids in a 10-min separation. Also, diffusion coefficients and electrophoretic mobilities may be measured with good accuracy. The low flow rate of capillary zone electrophoresis affects the performance of the sheath flow cuvette. Theory predicts and experiment verifies that the peak height In capillary zone electrophoresis with the sheath flow detector increases linearly with separation voltage. A model Is also presented for the sample stream radius expected in the sheath flow cuvette for analytes that undergo radial diffusion. © 1990, American Chemical Society. All rights reserved.