Introduction

The migration of charged particles under the influence of an electric field was discovered and characterized theoretically more than 100 years ago by Kolrausch et al. Foreseeing the possibility of separation of charged species through the application of a voltage, the term 'electrophoresis' was coined soon after. However, early attempts to use electrophoresis as an analytical tool were persistently frustrated by the existence of Joule heating, which acts to discount the electrophoretic effect. Thus a way of combatting the thermal effect during the electrophoretic process was needed. By 1950s, Tiselius et al. found that a variety of substances such as agarose and polymeric gels could serve as stabilizing agents in electro-phoretic analysis owing to their anticonvective properties. This eventually led to the creation of slab gel electrophoresis, which has become a fundamental technique for the study of proteins, DNA fragments and other biomacromolecules in life sciences and biotechnology. Notwithstanding its great success, slab gel electrophoresis has its drawbacks with respect to speed and automation when compared with contemporary chromatographic techniques such as high performance liquid chromatography (HPLC).

A straightforward way to speed up an electro-phoretic separation process is to apply higher electric fields, and this necessitates systems able to release the heat generated more efficiently. Electrophoresis with a tube as a separation channel is hence an attractive choice since the desired surface-to-volume ratio can be achieved by simply reducing the tube radius. Performing electrophoresis based on the tube format has an added advantage in that simultaneous detection may be implemented in a way analogous to HPLC, thus rendering the entire procedure fast and automatic. Running electrophoresis with a tube configuration was initiated by Hjerten as early as the 1960s, and further attempted by Virtanen et al. and Mikkers et al. in 1970s. During this period, the adopted inner diameters of tubes were in the range of 0.2-3 mm, and thermal effects confined the applied voltage to around 1000-2000 V, which was of the same order as in typical slab gel electrophoresis. As a consequence, despite these pioneering efforts to perform free solution electrophoresis with in-line monitoring, the full potential with respect to column performance was not yet attained. Also, complexity in instrumental design deterred follow-up by ordinary elec-trophoresis practitioners.

A milestone for column-based electrophoresis was set in the early 1980s, when Jorgenson et al. introduced capillary zone electrophoresis (CZE) with on-col-umn optical detection. They found that with the inner diameter of the capillaries scaled down to 80 |im, voltages as high as 30 kV could be applied without incurring overheating problems. Thus the separation time for most charged species, from small molecules to macromolecules, was shortened to less than 30 min, which is comparable to modern chromato-graphic methods. For the first time outstanding column efficiencies of several hundred thousand plates was routinely obtained. The unprecedented performance, relatively simple instrumentation, concurrent with the widespread availability of fused silica capillary columns by the mid-1980s quickly aroused the interests of both electrophoresis practitioners and chromatographers, thus making capillary electrophoresis (CE) one of the most exciting research areas. Today, it has become an indispensable branch of modern separation science. The powerful separation ability of CE was exemplified in an early electropherogram concerning the resolution of de-rivated peptides originated from egg white lysozyme (Figure 1).

This article serves as an introduction to CE. It covers the basic principles, various aspects of instrumentation, separation modes and major applications. Some future trends of CE are discussed in the final section.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment