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Mixed-mode electrokinetic chromatography of aromatic bases with two pseudo-stationary phases and pH control


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Zakaria, P, Macka, M and Haddad, PR 2003 , 'Mixed-mode electrokinetic chromatography of aromatic bases with two pseudo-stationary phases and pH control' , Journal of Chromatography A, vol. 997, No. 1-2 , pp. 207-218 , doi: 10.1016/S0021-9673(03)00064-5.

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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 β-cyclodextrin (β-CD) as pseudo-stationary phases. The separation mechanism was based on a combination of electrophoresis, ion-exchange interactions with PVS, and hydrophobic interactions with β-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 β-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, [β-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.

Item Type: Article
Authors/Creators:Zakaria, P and Macka, M and Haddad, PR
Keywords: Pyridines; Anilines; Amines; Picoline; Quinoline; Mixed-mode separations; Electrokinetic chromatography; Neural networks, artificial; Pseudo-stationary phases
Journal or Publication Title: Journal of Chromatography A
ISSN: 0021-9673
DOI / ID Number: 10.1016/S0021-9673(03)00064-5
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