Effect of sample stacking on resolution, calibration graphs and pH in capillary zone electrophoresis

Beckers, JL Jozef; Ackermans, MT Mariëtte

doi:10.1016/0021-9673(93)87051-m

Cited by 59 publications

(28 citation statements)

References 8 publications

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“…The ratio of overall effective mobilities of p-nitrophenol in these electrolyte systems was 5.91, illustrating that the contribution of differences in viscosiov ty is small and that the decrease in reef f is based mainly on micellar partitioning. In amplified sample stacking, peak shapes start to deteriorate with longer sample plugs, due to a mismatch in the EOF of the sample plug, and that of the electrolyte system [23]. For the m~ff-mediated sample stacking procedure, the curve starts to level off at higher injection constants, which is due also to an EOF mismatch.…”

Section: M'e'~f-mediated Sample Stackingmentioning

confidence: 99%

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Muijselaar

Claessens

Cramers

1997

Journal of Chromatography A

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Section: M'e'~f-mediated Sample Stackingmentioning

confidence: 99%

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Muijselaar

Claessens

Cramers

1997

Journal of Chromatography A

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“…The fast moving zones of highly concentrated Na 1 and Cl 2 under an electric field of reverse polarity induced pH changes at both boundaries of the sample zone to satisfy the electroneutrality overcoming the pH changes due to the mass imbalance of the hydrogen ions at the boundaries between the sample and the BGE [31]. When the pH-elevated zone moved toward the anode and met the pH-lowered zone, a significant pH junction was created.…”

Section: Introductionmentioning

confidence: 98%

“…As the rear boundary of Cl 2 moved toward the anode and the front boundary of Na 1 moved into the BGE zones, the OH 2 concentrations near the cathodic boundary of the sample zone increased to satisfy the electroneutrality condition and the pH started to increase above the BGE pH of 9.0. The pH increase at the cathodic side due to the charge imbalance caused by the migration of fast moving matrix ions in large numbers exceeded the pH lowering effect of the H 1 mass imbalance between the sample and BGE zones [31]. Similarly, the pH at the anodic side decreased (Fig.…”

mentioning

confidence: 94%

Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing

et al. 2003

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A dual stacking mechanism based on transient isotachophoresis (TITP) and induced pH junction focusing is demonstrated as a means to increase the concentration sensitivity in capillary electrophoresis of highly saline samples. When stacking was carried out with an unbuffered saline sample of fluorescein between two zones of low mobility background electrolyte at high pH under an electric field of reverse polarity, two transient peaks at both boundaries of the sample zone were observed. One peak at the rear boundary could be inferred as a transient isotachophoretic stacked zone. Through computer simulations of an unbuffered sample with a high concentration of sodium chloride, we showed that the fast moving zones of sodium and chloride ions induced pH changes at both boundaries to satisfy the electroneutrality condition and that the peak at the front boundary was due to the induced pH junction. To verify the pH changes, an indicator, thymol blue, was added to an NaCl solution and the color changes under an electric field were observed. The proposed mechanism was supported by observing the dual stacking procedure for an unbuffered sample of 4-nitrophenol and measuring additional sensitivity enhancements by dual stacking for ten weakly acidic compounds. For the ten analytes including nucleoside phosphates, every dual stacking of an unbuffered sample exhibited an additional enhancement up to 86% larger than that of usual transient isotachophoresis of the corresponding buffered sample without loss of separation efficiency and reproducibility. Therefore, it would be useful to skip over buffering in sample preparation for TITP, contrary to the general recommendation.

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“…For this purpose, field amplification [3,4] or sample stacking [5,6] is often applied. These techniques can result, however, in a disastrous decrease in separation power [7], especially for large sample volumes. Isotachophoresis (ITP) can also be used as preconcentration technique.…”

Section: Introductionmentioning

confidence: 99%

Isotachophoresis superimposed on capillary zone electrophoresis

Beckers

1993

Journal of Chromatography A

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Applying isotachophoresis (ITE') superimposed on capillary zone electrophoresis (CZE), which will be denoted the ITPlCZE mode, components migrate in an ITP way on top of a background electrolyte. In such an ITPKZE system the leading electrolyte consists of a mixture of an ionic species L, with a high mobility (the leading ion of the ITP system), an ionic species L, with low mobility (the co-ions of the ZE system) and buffering counter ions, whereas the terminating solution contains only the ionic species L, and the buffering counter ions. The zones of the components migrating in the ITPlCZE mode are very sharp owing to the self-correcting effect and the concentrations of the components are adapted to the concentration of the L, ions of the system. Calculated mobility windows are given, indicating which components can migrate in the ITP/CZE mode and features and possibilities of ITPICZE are discussed on the basis of several electropherograms.

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Effect of sample stacking on resolution, calibration graphs and pH in capillary zone electrophoresis

Cited by 59 publications

References 8 publications

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Migration behaviour of monovalent weak acids in micellar electrokinetic chromatography mobility model versus retention model

Dual stacking of unbuffered saline samples, transient isotachophoresis plus induced pH junction focusing

Isotachophoresis superimposed on capillary zone electrophoresis

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