title: On-line preconcentration of weak electrolytes by electrokinetic accumulation in CE: experiment and simulation.
abstract: A new on-line preconcentration technique was developed that makes possible to determine nanomolar concentrations of weak acidic analytes in CE. The method consists of long-running electrokinetic sample injection and stacking (electrokinetic immobilization) of the analytes at a boundary of two electrolytes with different pH values (pH 9.5 and 2.5) and consequent mobilization of the stacked uncharged analytes in a micellar system (containing SDS micelles). Several factors including buffer concentration, pH, applied voltage, time of preconcentration, and SDS concentration were tested to optimize the analysis method. An about 4600-fold increase of the sample concentration (in comparison with the standard CZE) can be achieved during the preconcentration step. Two preservatives applied in food industry -- benzoic acid and sorbic acid were used as model samples. The applicability of the proposed method in food analysis was demonstrated by determination of nanomolar concentrations of benzoic acid in sunflower oil. An extended version of the computer program Simul was used for modeling both the preconcentration and mobilization processes taking place in the capillary.
authors: Department of Analytical Chemistry, Palacký University, Trída Svobody, Olomouc, Czech Republic.
authors: Jana
authors: J
authors: Horáková
authors: Jan
authors: J
authors: Petr
authors: Vítezslav
authors: V
authors: Maier
authors: Eva
authors: E
authors: Tesarová
authors: Libor
authors: L
authors: Veis
authors: Daniel W
authors: DW
authors: Armstrong
authors: Bohuslav
authors: B
authors: Gas
authors: Juraj
authors: J
authors: Sevcík
mesh_terms: D019817:Benzoic Acid / Q000032:analysis; D002021:Buffers; D003198:Computer Simulation; D004573:Electrolytes / Q000032:analysis*; D019075:Electrophoresis, Capillary / Q000295:instrumentation* / Q000379:methods*; D005504:Food Analysis / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013011:Sorbic Acid / Q000032:analysis
chemical_list: D002021:Buffers; D004573:Electrolytes; D012967:Sodium Dodecyl Sulfate; D019817:Benzoic Acid; D013011:Sorbic Acid