Application of an electroosmotic flow gradient in capillary zone electrophoresis separations

• Published in: Journal of liquid chromatography & related technologies 1998-11, Vol.21 (19), p.2957-2976
• Main Authors: Soontornniyomkij, B, Chen, S, Minnoor, E.S, Pietrzyk, D.J
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; ions; magnesium; Other chromatographic methods
• ISSN: 1082-6076; 1520-572X
• DOI: 10.1080/10826079808006879

Resolution can be enhanced and separation time shortened in the capillary zone electrophoresis (CZE) separation of complex mixtures of acidic analytes that differ in pK a values but have similar electrophoretic mobilities through an electroosmotic flow (EOF) gradient. The EOF gradient is created by a dynamic dilution of Mg 2+ in the inlet reservoir, which is in the buffer as an EOF modifier, as the electrophoresis proceeds. Initially, the Mg 2+ buffer enters the capillary by electromigration and produces a low EOF compared to the absence of Mg 2+ . As the Mg 2+ in the buffer in the inlet reservoir is diluted dynamically the EOF from the inlet side increases dynamically. Migration times for the fast-moving analytes are increased at a high Mg 2+ buffer concentration in the initial stages of the separation while the migration times for the slow-moving analytes are shortened by the EOF increase generated as Mg 2+ is diluted during the gradient. The dynamic gradient, where EOF starts low and increases, influences analyte migration time, resolution, and separation time. The effect of initial Mg 2+ buffer concentration, the rate of Mg 2+ dilution, and the time delay in generating the gradient are parameters that can be altered to influence the CZE gradient separation. Several model analyte mixtures are used to illustrate the scope of the EOF gradient conditions. † nee B. Chanthawat