Peaks in capillary zone electrophoresis: Fact or fiction

Beckers, JL Jozef; Boček, Petr

doi:10.1002/(sici)1522-2683(19990301)20:3<518::aid-elps518>3.0.co;2-f

Cited by 24 publications

(8 citation statements)

References 17 publications

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“…Consequently, so-called unsafe mobility regions have been defined [18], being the region close to the mobility of SZs (m SZ 6 10%), where the analytical evaluation of the peaks of sample components is deteriorated or even impossible. Generally, the migration of SZs and the shape (fronting/tailing) and polarity (peak/dip) of the peaks of analytes are closely interrelated as shown already in several papers [19][20][21][22][23]. The theoretical approaches to these problems can be found elsewhere [20,24].…”

Section: Introductionmentioning

confidence: 84%

System zones in capillary zone electrophoresis

2001

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This paper brings an overview of system zones (SZs) in capillary zone electrophoresis (CZE) and their effects upon the migration of zones of analytes. It is shown that the formation and migration of SZs is an inherent feature of CZE, and that it depends predominantly on the composition of an actual background electrolyte (BGE). One can distinguish between stationary SZs and migrating SZs. Stationary SZs, which move due to the electroosmotic flow only, are induced in any BGE by sample injection. Migrating SZs may be induced by a sample injection in BGEs which show at least one of the following features: (i) BGE contains two or more co-ions, (ii) BGE has low or high pH whereby H+ or OH- act as the second co-ion, and (iii) BGE contains multivalent weak acids or bases. SZs do not contain any analyte and show always BGE-like composition. They contain components of the BGE only and the concentrations of these components are different from their values in the original BGE. Providing that some of the ionic components of the BGE are visible by the detector, the migrating SZs can be detected and they are present as system peaks/dips in the electropherogram. It is shown that a migrating SZ may be characterized by its mobility, and examples are given how this mobility can depend on the composition of the BGE. Further, the effects of the migrating SZs (either visible or not visible by the detector) upon the zones of analytes are presented and the typical disturbances of the peaks (extra broadening, zig-zag form, schizophrenic behavior) are exemplified and discussed. Finally, some conclusions are presented how to cope with the SZs in practice. The proposed procedure is based on the theoretical predictions and/or measurements of the mobilities of SZs and on the so-called unsafe region. Then, such operational conditions should be selected where the unsafe region is outside of the required analytical window.

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Section: Introductionmentioning

confidence: 84%

System zones in capillary zone electrophoresis

2001

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“…The number N -2 is positive only if the number of BGE components is 3 or higher, i.e., a BGE with two components does not provide any system zone, a BGE with three components provides one system zone, a BGE with four components provides two system zones, etc. Recently it was shown that at conditions when a solvent ion behaves as a significant separate constituent (e.g., at high or low pH), the value of N increases by 1 [6,7] (see Section 4.1).…”

Section: The Origin Of System Zonesmentioning

confidence: 99%

“…Even in such cases, however, the models based on the movingboundary equation are successfully applicable by using iterative calculation procedures where the number and mobilities of all system zones are found by finding for which analyte mobilities infinite values of suitable zone properties are obtained. As such a property not only the velocity slope [8] can be used but also, e.g., transfer ratio, pH, conductivity ratio (k/k BGE ) or concentration of the counter-or co-ions [7,13,14]. Graphical presentations as Peak Shape Diagrams (a S X map in a pK X vs. u X network [15]) and SystCharts (above -mentioned quantities vs. u X [16]) were shown to be very helpful in predicting of the properties of system zones in various BGEs [5,6,8,13,14,[17][18][19][20][21].…”

Section: Models Based On the Moving-boundary Equationmentioning

confidence: 99%

“…It has been demonstrated that such systems show a system zone even if they have only one co-ion and this system zone was assigned to the effect of the H 1 /OH 2 constituent [7,18]. Explicit equations were derived [18] for the mobility of the system zone in the simple case of a BGE consisting of one weak acid HA and one weak base B.…”

Section: The Role Of Solvent Ionsmentioning

confidence: 99%

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Theory of system zones in capillary zone electrophoresis

2002

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In the last years, it has been shown that the formation and migration of system zones is an inherent feature of capillary zone electrophoresis (CZE) and that it depends predominantly on the composition of an actual background electrolyte (BGE). In most of the currently used BGEs, the SZs are invisible by the UV absorbance detection system, however, the comigration of SZs with the zones of analytes deteriorates the analytical performance of CZE and may be fatal for its utilization. Therefore, the theoretical predictions of the existence and migration of SZs is of key importance for the expediency of CZE. This is a review of the theoretical treatments of SZs which reveals the origin and the properties of SZs and shows how to cope with them. Also, a table of some typical BGEs is presented where the existence and mobilities of SZs are given.

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“…The term "system peaks" was introduced to denote these peaks. Over the last several years, a number of papers have addressed this topic [1][2][3][4][5][6][7][8][9]. Among the approaches, the migration vacancy provides a simple model to explain the origin of the system peaks [6].…”

Section: Introductionmentioning

confidence: 99%