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Double gradient ion chromatography using short monolithic columns modified with a long chained zwitterionic carboxybetaine surfactant


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O'Riordain, C and Nesterenko, EP and Nesterenko, PN and Paull, B (2006) Double gradient ion chromatography using short monolithic columns modified with a long chained zwitterionic carboxybetaine surfactant. Journal of Chromatography A, 1109 (1). pp. 111-119. ISSN 0021-9673

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The rapid separation of inorganic anions on short monolithic columns permanently coated with a long chained zwitterionic carboxybetaine-type surfactant is shown. The surfactant, N-dodecyl-N,N-(dimethylammonio)undecanoate (DDMAU), was used to coat 2.5, 5.0 and 10 cm long reversed-phase silica monoliths, resulting in a permanent zwitterionic exchange surface when used with aqueous based eluents. The unique structure of the surfactant results in a charge double layer structure on the surface of the stationary phase, with strong internal anionic and weak external cationic exchange groups. The dissociation of the weak external carboxylic acid group acts to shield the inner anionic exchange site, resulting in substantial effective capacity changes with eluent pH. Utilising this effect with the application of an eluent pH gradient, simultaneously combined with eluent flow-rate gradients, very rapid simultaneous separations of both weakly retained anions and strongly retained polarisable anions was possible, with up to 10-fold decreases in overall run times. Coating stability and retention times under isocratic and isofluentic eluent conditions were shown to be reproducible over >450 repeat injections, with peak efficiency values averaging 29,000 N/m for the 2.5 cm column and 42,000 N/m for the 10 cm monolithic column, again under isocratic elution conditions.

Item Type: Article
Keywords: Ion chromatography; Inorganic anions; Monolithic column; N-dodecyl-N,N-(dimethylammonio)undecanoate
Journal or Publication Title: Journal of Chromatography A
Page Range: pp. 111-119
ISSN: 0021-9673
Identification Number - DOI: 10.1016/j.chroma.2006.01.002
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Date Deposited: 17 Sep 2008 04:28
Last Modified: 18 Nov 2014 03:50
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