COMPUTER-ASSISTED OPTIMIZATION OF SEPARATIONS IN CAPILLARY ZONE ELECTROPHORESIS

A computer optimization routine has been developed which is capable of evaluating the quality of electrophoretic separations under a variety of operational conditions, The program includes theoretical models fo r electrophoretic and electroosmotic migration processes as well as a simple rationale for zone dispersion, The electrophoretic migration su broutine is based on classical equilibrium calculations and requires k nowledge of the solute dissociation constant(s) and electrophoretic mo bility(s), in the electroosmotic migration subroutine, the response of the fused-silica capillary surface to changes in buffer composition i s modeled in analogy to an ion-selective electrode, A mathematical fun ction that relates the zeta potential to the pH and sodium concentrati on of the buffer solution is required. The migration time of each solu te is then calculated from the sum of its effective electrophoretic mo bility and the electroosmotic mobility, The temporal width of each sol ute zone is derived from contributions to variance resulting from long itudinal diffusion and a finite injection and detection volume, The re solution between adjacent zones is estimated, and the overall quality of the separation is assessed by means of an appropriate response func tion, As input to the optimization program, variables related to the b uffer composition (pH, ionic strength, concentration), capillary dimen sions (diameter, length), and instrumental parameters (applied voltage or current) are considered, By methodically varying the input paramet ers and evaluating the overall quality of the separation, this compute r program can be used to predict the experimental conditions required for optimal separation of the solutes, The computer optimization routi ne was experimentally validated with a mixture of nucleotide mono- and diphosphates in phosphate buffer solutions, with average errors in th e effective electrophoretic mobility, electroosmotic mobility, and zon e variance of 2.9, 2.3, and 9.4%, respectively.