Computer-Assisted Optimization of Separations in Capillary Zone Electrophoresis

• Published in: Analytical chemistry (Washington) 1997-01, Vol.69 (2), p.152-164
• Main Authors: McGuffin, Victoria L, Tavares, Marina F. M
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Computers; Exact sciences and technology; Other chromatographic methods; Software
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac961048r

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 for electrophoretic and electroosmotic migration processes as well as a simple rationale for zone dispersion. The electrophoretic migration subroutine is based on classical equilibrium calculations and requires knowledge of the solute dissociation constant(s) and electrophoretic mobility(s). In the electroosmotic migration subroutine, the response of the fused-silica capillary surface to changes in buffer composition is modeled in analogy to an ion-selective electrode. A mathematical function that relates the zeta potential to the pH and sodium concentration of the buffer solution is required. The migration time of each solute is then calculated from the sum of its effective electrophoretic mobility and the electroosmotic mobility. The temporal width of each solute zone is derived from contributions to variance resulting from longitudinal diffusion and a finite injection and detection volume. The resolution between adjacent zones is estimated, and the overall quality of the separation is assessed by means of an appropriate response function. As input to the optimization program, variables related to the buffer composition (pH, ionic strength, concentration), capillary dimensions (diameter, length), and instrumental parameters (applied voltage or current) are considered. By methodically varying the input parameters and evaluating the overall quality of the separation, this computer program can be used to predict the experimental conditions required for optimal separation of the solutes. The computer optimization routine was experimentally validated with a mixture of nucleotide mono- and diphosphates in phosphate buffer solutions, with average errors in the effective electrophoretic mobility, electroosmotic mobility, and zone variance of 2.9, 2.3, and 9.4%, respectively.