CONTRIBUTION OF CAPILLARY COILING TO ZONE DISPERSION IN CAPILLARY ZONE ELECTROPHORESIS

A mathematical model of the deformation of the analyte zone in capilla ry zone electrophoresis (CZE) due to capillary coiling is presented an d the influence of capillary coiling on the distribution of electric c urrent density inside the capillary is described. The model gives a qu antitative description of the potential contribution of capillary coil ing to the total zone dispersion in CZE. The zone broadening caused by capillary coiling is calculated as the difference of migration distan ces of the particles migrating at the inner circumference of the capil lary coil and those migrating at the outer circumference. This differe nce is shown to be directly proportional to the capillary diameter and to the number of capillary coils, i.e. indirectly proportional to the radius of the capillary coils into which the capillary of the given l ength is coiled. The contribution of capillary coiling to the total zo ne dispersion is compared with the contribution of the longitudinal di ffusion of low and high molecular mass analytes and bioparticles. It i s shown that, especially in the case of CZE separation of macromolecul es and particles, capillary coiling can significantly decrease the sep aration efficiency, For that reason the small radius coiling of the ca pillary column in the CZE apparatuses should be avoided.