title: Mixed-mode electrokinetic chromatography of aromatic bases with two pseudo-stationary phases and pH control.
abstract: The electrokinetic chromatographic (EKC) separation of a series of aromatic bases was achieved utilising an electrolyte system comprising an anionic soluble polymer (polyvinylsulfonic acid, PVS) and a neutral beta-cyclodextrin (beta-CD) as pseudo-stationary phases. The separation mechanism was based on a combination of electrophoresis, ion-exchange interactions with PVS, and hydrophobic interactions with beta-CD. The extent of each chromatographic interaction was independently variable, allowing for control of the separation selectivity of the system. The ion-exchange and the hydrophobic interactions could be varied by changing the PVS and the beta-CD concentrations, respectively. Additionally, mobilities of the bases could be controlled by varying pH, due to their large range of pKa values. The separation system was very robust with reproducibility of migration times being <2% RSD. The two-dimensional parameter space defined by the two variables, [beta-CD] and %PVS, was modelled using a physical model derived from first principles. This model gave very good correlation between predicted and observed mobilities (r2=0.999) for the 13 aromatic bases and parameters derived from the model agreed with the expected ion-exchange and hydrophobic character of each analyte. The complexity of the mathematical model was increased to include pH and this three-dimensional system was modelled successfully using an artificial neural network (ANN). Optimisation of both the two-dimensional and three-dimensional systems was achieved using the normalised resolution product and minimum resolution criteria. An example of using the ANN to predict conditions needed to obtain a separation with a desired migration order between two of the analytes is also shown.
authors.affiliation: Department of Chemistry, University of Tasmania, GPO Box 252-75, Hobart, Tasmania 7001, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Zakaria
authors.forename: Miroslav
authors.initials: M
authors.lastname: Macka
authors.forename: Paul R
authors.initials: PR
authors.lastname: Haddad
mesh_terms: D000588:Amines / Q000032:analysis*; D000814:Aniline Compounds / Q000032:analysis*; D001596:Benzylamines / Q000032:analysis; D002845:Chromatography / Q000379:methods*; D002852:Chromatography, Ion Exchange; D003505:Cyclodextrins; D019075:Electrophoresis, Capillary / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D008433:Mathematics; D016571:Neural Networks, Computer; D011145:Polyvinyls; D011725:Pyridines / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013451:Sulfonic Acids; D047392:beta-Cyclodextrins
chemical_list: D000588:Amines; D000814:Aniline Compounds; D001596:Benzylamines; D003505:Cyclodextrins; D011145:Polyvinyls; D011725:Pyridines; D013451:Sulfonic Acids; D047392:beta-Cyclodextrins; C008959:lyapolate; C030796:benzylamine; C031215:betadex; C023650:aniline