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Inherent peak compression of charged analytes in electrochromatography
Author(s) -
Nischang Ivo,
Tallarek Ulrich
Publication year - 2009
Publication title -
journal of separation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.72
H-Index - 102
eISSN - 1615-9314
pISSN - 1615-9306
DOI - 10.1002/jssc.200900436
Subject(s) - electrochromatography , chemistry , analyte , analytical chemistry (journal) , concentration polarization , polarization (electrochemistry) , chemical physics , particle (ecology) , electric field , dispersion (optics) , ionic strength , capillary electrochromatography , chromatography , capillary electrophoresis , optics , biochemistry , oceanography , physics , quantum mechanics , membrane , aqueous solution , geology
This work resolves peak compression of charged analytes in CEC with strong cation‐exchange stationary phase particles. By combining electrochromatographic peak shape analysis with the results of numerical simulations and confocal laser scanning microscopy in the packed capillaries, we identify electrical field‐induced concentration polarization as the key physical phenomenon responsible for the inherent existence of local electrical field gradients on the scale of an individual support particle. Consequently, positive and negative field gradients exist between and inside the particles along the whole packing. Their intensity depends on the particles cation‐selectivity (governed by the particles volume charge density and the mobile phase ionic strength) and the applied field strength. The interplay of these local field gradients with the analytes retention (intraparticle adsorption) determines whether fronting, tailing, or spiked analyte peaks are observed, and it provides a mechanism by which strongly retained analytes can be eluted over long distances with little zone dispersion. Our analysis explains the “anomalous” peak compression effects with strong cation‐exchange particles, which have been reported more than a decade ago (Smith, N. W., Evans, M. B., Chromatographia 1995, 41 , 197–203) and since then remained largely unresolved.