Beckers J L, Gebauer P, Bocek P
Eindhoven University of Technology, Department of Chemistry (SPO), The Netherlands.
Electrophoresis. 2001 Oct;22(17):3648-58. doi: 10.1002/1522-2683(200109)22:17<3648::AID-ELPS3648>3.0.CO;2-Q.
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.
本文概述了毛细管区带电泳（CZE）中的系统区带（SZs）及其对分析物区带迁移的影响。结果表明，SZs的形成和迁移是CZE的固有特征，且主要取决于实际背景电解质（BGE）的组成。可区分固定SZs和迁移SZs。固定SZs仅因电渗流而移动，通过进样在任何BGE中都会产生。迁移SZs可能由进样在具有以下至少一种特征的BGE中诱导产生：（i）BGE包含两种或更多种共离子；（ii）BGE具有低pH或高pH，其中H⁺或OH⁻作为第二种共离子；（iii）BGE包含多价弱酸或弱碱。SZs不包含任何分析物，且始终呈现类似BGE的组成。它们仅包含BGE的成分，且这些成分的浓度与原始BGE中的值不同。如果BGE的某些离子成分可被检测器检测到，则迁移的SZs可被检测到，并且它们以系统峰/谷的形式出现在电泳图中。结果表明，迁移的SZs可通过其迁移率来表征，并给出了该迁移率如何取决于BGE组成的示例。此外，还介绍了迁移的SZs（无论检测器是否可见）对分析物区带的影响，并举例说明了峰形典型的干扰情况（额外展宽、锯齿形、分裂行为）并进行了讨论。最后，给出了一些关于在实际操作中如何应对SZs的结论。所提出的方法基于SZs迁移率以及所谓不安全区域的理论预测和/或测量结果。然后，应选择这样的操作条件，使不安全区域位于所需分析窗口之外。
