Peak compression effects in capillary electrochromatography

Enlund, Anna Maria; Andersson, Margareta; Hagman, Gunnar

doi:10.1016/j.chroma.2004.04.080

Cited by 6 publications

(8 citation statements)

References 20 publications

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“…The result was further verified by the injection of sample solution for at least 15 times. As atenolol eluted closely behind the EOF marker, a case very similar to the peak compression effect reported by Enlund et al [23,24], it is reasonable to believe that the "continuous stacking" mechanism may also be responsible for such a phenomenon. The influence of phosphate concentration on the separation efficiencies of b-blockers was investigated, and the obtained results are shown in Figure 5.…”

Section: Separation Of Basic Analytes On a Monolithic Silica Columnsupporting

confidence: 81%

Preparation of monolithic silica column with strong cation‐exchange stationary phase for capillary electrochromatography

Xie¹,

Hu²,

Xiao³

et al. 2005

J of Separation Science

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Preparation of monolithic silica column with strong cation-exchange stationary phase for capillary electrochromatography A monolithic silica based strong cation-exchange stationary phase was successfully prepared for capillary electrochromatography. The monolithic silica matrix from a solgel process was chemically modified by treatment with 3-mercaptopropyltrimethoxysilane followed by a chemical oxidation procedure to produce the desired function. The strong cation-exchange stationary phase was characterized by its substantial and stable electroosmotic flow (EOF), and it was observed that the EOF value of the prepared column remained almost unchanged at different buffer pH values and slowly decreased with increasing phosphate concentration in the mobile phase. The monolithic silica column with strong cation-exchange stationary phase has been successfully employed in the electrochromatographic separation of b-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). The column efficiencies for the tested b-blockers varied from 210,000 to 340,000 plates/m. A peak compression effect was observed for atenolol with the mobile phase having a low phosphate concentration.

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Section: Separation Of Basic Analytes On a Monolithic Silica Columnsupporting

confidence: 81%

Preparation of monolithic silica column with strong cation‐exchange stationary phase for capillary electrochromatography

Xie¹,

Hu²,

Xiao³

et al. 2005

J of Separation Science

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“…Most data reported on peak compression in CEC, which are not (or not exclusively) caused by sample composition-induced system zones, are consistent with the operational domain of the CPbased electrical field gradients. This particularly explains the anomalous peak compression effects with SCX stationary phases that were reported more than a decade ago and since then have remained largely unresolved [24][25][26][27]52].…”

Section: Introductionmentioning

confidence: 99%

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Nischang¹,

Höltzel²,

Tallarek³

2010

Electrophoresis

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We analyze the systematic and substantial electrical field-dependence of electrochromatographic retention for four counterionic peptides ([Met5]enkephalin, oxytocin, [Arg8]vasopressin, and luteinizing hormone releasing hormone (LHRH) ) on a strong cation-exchange (SCX) stationary phase. Our experiments show that retention behavior in the studied system depends on the charge-selectivity of the stationary phase particles, the applied voltage, and the peptides' net charge. Retention factors of twice positively charged peptides ([Arg8]vasopressin and LHRH at pH 2.7) decrease with increasing applied voltage, whereas lower charged peptides (oxytocin and [Met5]enkephalin at pH 2.7, [Arg8]vasopressin and LHRH at pH 7.0) show a concomitant increase in their retention factors. The observed behavior is explained on the basis of electrical fieldinduced concentration polarization (CP) that develops around the SCX particles of the packing. The intraparticle concentration of charged species (buffer ions, peptides) increases with increasing applied voltage due to diffusive backflux from the enriched CP zone associated with each SCX particle. For twice charged and on the SCX phase strongly retained peptides the local increase in mobile phase ionic strength reduces the electrostatic interactions with the stationary phase, which explains the decrease of retention factors with increasing applied voltage and CP intensity. Lower charged and weaker retained peptides experience a much stronger relative intraparticle enrichment than the twice-charged peptides, which results in a net increase of retention factors with increasing applied voltage. The CP-related contribution to electrochromatographic retention of peptides on the SCX stationary phase is modulated by the applied voltage, the mobile phase ionic strength, and the peptides' net charge and could be used for selectivity tuning in difficult separations.

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“…The results which we present on inherent CP-based peak compression of charged analytes in CEC also explain the still largely unresolved observations that have been made in that regard in the past [58] and since then received often controversial (and emotional) discussions. Our conclusions in this direction can be summarized as follows.…”

Section: Discussionmentioning

confidence: 63%

“…In this work, we demonstrate that "anomalous" peak shapes and compression effects, which have been reported for polar (cationic) drugs, as summarized in Enlund et al [58], can be rationalized by the unique existence of CP in capillaries packed with strong cationexchange (SCX) particles as well as the sensitive response of CP to the applied field strength, mobile phase ionic strength, and cation-selectivity of the particles. We present and analyze the peak shapes of single positively charged drugs in dependence on the applied field strength and mobile phase ionic strength using 50 lm id capillaries packed with 5 lm sized SCX particles.…”

Section: Introductionmentioning

confidence: 83%

Inherent peak compression of charged analytes in electrochromatography

Nischang

Tallarek²

2009

J of Separation Science

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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.

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Peak compression effects in capillary electrochromatography

Cited by 6 publications

References 20 publications

Preparation of monolithic silica column with strong cation‐exchange stationary phase for capillary electrochromatography

Preparation of monolithic silica column with strong cation‐exchange stationary phase for capillary electrochromatography

Electrochromatographic retention of peptides on strong cation‐exchange stationary phases

Inherent peak compression of charged analytes in electrochromatography

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