Summary
Various methods are currently under investigation to improve concentration detection limits in capillary electrophoresis (CE). Stacking and isotachophoresis coupled in-line with free-solution electrophoresis are the techniques most frequently used. Samples containing a high and/or varying salt concentration, such as urine and serum, are difficult to handle: usually a significant loss in electrophoretic efficiency is observed compared with samples possessing a low electric conductivity. In the present paper an alternative approach is developed, i.e. a liquid chromatographic (LC)-type of sample pretreatment is coupled on-line with CE. To demonstrate the feasibility of this approach, the separation of three model compounds (benzoates) in water containing up to 400 mM of sodium chloride is studied using a 50 mM borate CE buffer of pH 9.5. The direct injection of samples with high salt concentrations in CE results in peak splitting and/or serious band broadening. These problems are not encountered when using the present LC-CE system. In addition, the detection limits are hardly influenced by the salt concentration of the sample; this underlines the robustness of the system.
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Veraart, J.R., Gooijer, C., Lingeman, H. et al. On-line chromatographic pretreatment of samples with varying salt concentrations for capillary electrophoresis. Chromatographia 44, 581–588 (1997). https://doi.org/10.1007/BF02466659
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DOI: https://doi.org/10.1007/BF02466659