Sample stacking in CZE using dynamic thermal junctions II: Analytes with high dpKa/dT crossing a single thermal junction in a BGE with low dpH/dT

• Published in: Electrophoresis 2009-05, Vol.30 (9), p.1510-1515
• Main Authors: Mandaji, Marcos, Rübensam, Gabriel, Hoff, Rodrigo Barcellos, Hillebrand, Sandro, Carrilho, Emanuel, Kist, Tarso Ledur
• Format: Article
• Language: English
• Subjects: Algorithms; Amino acids; Amino Acids - chemistry; Band compression; CZE; Electric Conductivity; Electrolytes - chemistry; Electrophoresis, Capillary - instrumentation; Electrophoresis, Capillary - methods; Equipment Design; Ethanolamine - chemistry; Hydrogen-Ion Concentration; Lysine - chemistry; Models, Theoretical; Naphthalenes - chemistry; Sample stacking; Temperature; Thermal junctions; Viscosity
• ISSN: 0173-0835; 1522-2683
• DOI: 10.1002/elps.200800585

In a previous work [M. Mandaji, et al., this issue] a sample stacking method was theoretically modeled and experimentally demonstrated for analytes with low dpKa/dT (analytes carrying carboxylic groups) and BGEs with high dpH/dT (high pH-temperature-coefficients). In that work, buffer pH was modulated with temperature, inducing electrophoretic mobility changes in the analytes. In the present work, the opposite conditions are studied and tested, i.e. analytes with high dpKa/dT and BGEs that exhibit low dpH/dT. It is well known that organic bases such as amines, imidazoles, and benzimidazoles exhibit high dpKa/dT. Temperature variations induce instantaneous changes on the basicity of these and other basic groups. Therefore, the electrophoretic velocity of some analytes changes abruptly when temperature variations are applied along the capillary. This is true only if BGE pH remains constant or if it changes in the opposite direction of pKa of the analyte. The presence of hot and cold sections along the capillary also affects local viscosity, conductivity, and electric field strength. The effect of these variables on electrophoretic velocity and band stacking efficacy was also taken into account in the theoretical model presented. Finally, this stacking method is demonstrated for lysine partially derivatized with naphthalene-2,3-dicarboxaldehyde. In this case, the amino group of the lateral chain was left underivatized and only the alpha amino group was derivatized. Therefore, the basicity of the lateral amino group, and consequently the electrophoretic mobility, was modulated with temperature while the pH of the buffer used remained unchanged.