title: Influence of high-conductivity buffer composition on field-enhanced sample injection coupled to sweeping in CE.
abstract: The aim of this work was to clarify the mechanism taking place in field-enhanced sample injection coupled to sweeping and micellar EKC (FESI-Sweep-MEKC), with the utilization of two acidic high-conductivity buffers (HCBs), phosphoric acid or sodium phosphate buffer, in view of maximizing sensitivity enhancements. Using cationic model compounds in acidic media, a chemometric approach and simulations with SIMUL5 were implemented. Experimental design first enabled to identify the significant factors and their potential interactions. Simulation demonstrates the formation of moving boundaries during sample injection, which originate at the initial sample/HCB and HCB/buffer discontinuities and gradually change the compositions of HCB and BGE. With sodium phosphate buffer, the HCB conductivity increased during the injection, leading to a more efficient preconcentration by staking (about 1.6 times) than with phosphoric acid alone, for which conductivity decreased during injection. For the same injection time at constant voltage, however, a lower amount of analytes was injected with sodium phosphate buffer than with phosphoric acid. Consequently sensitivity enhancements were lower for the whole FESI-Sweep-MEKC process. This is why, in order to maximize sensitivity enhancements, it is proposed to work with sodium phosphate buffer as HCB and to use constant current during sample injection.
authors.affiliation: Chimie ParisTech, Laboratory of Physicochemistry of Electrolytes, Colloids and Analytical Sciences, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Anres
authors.forename: Nathalie
authors.initials: N
authors.lastname: Delaunay
authors.forename: Jérôme
authors.initials: J
authors.lastname: Vial
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Thormann
authors.forename: Pierre
authors.initials: P
authors.lastname: Gareil
mesh_terms: D002021:Buffers; D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D003198:Computer Simulation; D004553:Electric Conductivity; D019075:Electrophoresis, Capillary; D008956:Models, Chemical; D010756:Phosphoric Acids / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry
chemical_list: D002021:Buffers; D010756:Phosphoric Acids; D012972:Sodium Hydroxide; C030242:phosphoric acid